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2023 | Buch

Proceedings of The 17th East Asian-Pacific Conference on Structural Engineering and Construction, 2022

EASEC-17, Singapore

herausgegeben von: Guoqing Geng, Xudong Qian, Leong Hien Poh, Sze Dai Pang

Verlag: Springer Nature Singapore

Buchreihe : Lecture Notes in Civil Engineering


Über dieses Buch

This book presents articles from The 17th East Asian-Pacific Conference on Structural Engineering and Construction, 2022, organized by National University of Singapore. These peer-reviewed articles, authored by professional engineers, academics and researchers, highlight the recent research and developments in structural engineering and construction, embracing the theme- “Towards a Resilient and Sustainable City”. The papers presented in this proceeding provide in-depth discussions with key insights into the future research, development and engineering translation in structural engineering and construction.



Sustainable Binding Materials

Study of Methods for Improving Strength and Durability of Low-Quality Recycled Aggregate Concrete

In recent years, the amount of concrete waste is increasing every year by demolishing and renewing of concrete structures in Japan. In addition, it is expected to continue to increase in the future. In addition, there is a concern about the decrease of disposal sites, so it is necessary to have an effective method to use concrete waste. As an effective method of using concrete waste, the use of recycled aggregate can be considered. In order to promote the use of recycled aggregate, it is necessary to promote the use of low-quality recycled aggregate that can be produced with low energy and low cost. However, the strength and durability of concrete using low-quality recycled aggregate are significantly lower than those using normal aggregate. In previous studies, we examined the improving methods of mortar using low-quality recycled fine aggregate and concrete using low-quality recycled coarse aggregate. It was found that accelerated carbonation of recycled aggregate was optimal for mortar using low-quality recycled fine aggregate, and addition of C–S–H type accelerator was optimal for concrete using low-quality recycled coarse aggregate. Therefore, in this study, we aimed to improve the strength and durability of concrete using both low-quality recycled fine and coarse aggregate, so we examined the improving methods and its mechanism. There are two methods to improve the strength and durability of concrete using low-quality recycled aggregate: accelerated carbonation of recycled aggregate and addition of C–S–H type accelerator. As a result, it was found that the combinations of accelerated carbonation of recycled fine aggregate and addition of C–S–H type accelerator had a high improving effect in concrete using both low-quality recycled fine and coarse aggregate.

R. Yuya, N. Matsuda, M. Kojima, T. Iyoda
A Study on Strength and Durability of Mortar Using Low-quality Recycled Fine Aggregate with Accelerated Carbonation

Recycled aggregate produced from demolished concrete and waste fresh concrete are classified into three types of quality using the density in oven-dry condition and water absorption ratio in Japan. Among the three types, compared to medium and high quality recycled aggregate (M and H), low quality recycled aggregate (L) can be produced with less energy and cost, and reduces the generation of fine powder by-product. However, concrete made from L have problems are it has lower strength and greater length change due to drying shrinkage. When considering the widespread use of L, these must be improved with less cost. For these modifications, we have been investigating the use of CO2 gas for accelerated carbonation technology. This technology focuses on the carbonation mechanism of concrete and blows CO2 gas on recycled aggregate to carbonate the cement paste that are attached mortar. It has been found that the physical properties of recycled fine aggregate are greatly improved using this technology. Therefore, to investigate the effect of recycled fine aggregate with accelerated carbonation on the hardened samples, we conducted tests on mortars made from that fine aggregate. It has shown that mortar has improved strength and durability due to the reduction of mortar voids attached on recycled fine aggregate. Especially, we reported that there was a large improvement in the out of specification of L (outside of L). There is a difference in amount of fine powder. L contains 3% fine powder, while outside of L contains 12%. We considered that the fine powder influenced the hardened samples. Therefore, in this study we focused on the granularity, such as fine powder of low quality recycled fine aggregate and conducted tests on mortar to compare the difference in the effect of accelerated carbonation modification technology.

Y. Inoue, N. Matsuda, Y. Nishioka, T. Iyoda
Experimental Study to Improve Performance of Two-Stage Concrete Without Injection Focusing on the Interfacial Transition Zone

Two-stage concrete (TSC), also known as preplaced aggregate concrete, prepacked concrete, and rock-filled concrete, is a non-conventional concrete with an unusual construction method. It is produced by firstly placing the coarse aggregate into the formwork and after that, the voids are filled with a high-flow mortar mixture. This type of concrete has been applied in mass concrete, underwater concrete, and repair and strengthening of existing structures with economical and technical benefits. Previous studies showed that the interfacial transition zone between the coarse aggregate and the cementitious material has a primary influence on TSC, affecting the performance of hardened concrete. Also, more than the mechanical resistance of the coarse aggregate, other factors such as shape, good particle size distribution, combined with a mortar with non-shrinkage, non-segregation characteristics, and good flowability are important to achieve satisfactory performance of TSC. In this experimental study, several types of admixtures (C–S–H type hardening accelerator and three types of expansive mineral admixtures) were added to a premixed high flow mortar to improve the interfacial transition zone between aggregate and mortar of TSC blocks without injection. Measurements of porosity, air permeability coefficient, and compressive strength were conducted for TSC cores and conventional concrete specimens. Experimental results showed that the use of Calcium Oxide (CaO) expansive admixture was the most effective method evaluated and that there is a high potential to expand applications of the TSC produced without injection, as it was possible to improve significantly both mechanical performance and mass transfer resistance, reaching similar values when compared to conventional concrete.

Karen Midori Masunaga, Tomoki Nagoya, Takeshi Iyoda
Application of Granite Fines to Substitute Sand in Concrete Production

Nowadays, sustainable construction by using alternative concrete materials has been advocated around the globe due to the exhaustion of major sources of natural sand (NS), compounded with environmental and ecological considerations. In the meantime, a huge amount of granite fines (GF) as a by-product of crushing and sizing of granite in production of building stone for masonry industry, tile, coarse aggregate for the concrete industry, etc. are produced every year which generally treated as waste. And the landfilling of them causes serious environmental problems. Considering the stable source and sand-like physical properties of GF, it can serve as an ideal alternative material to substitute sand as the fine aggregate component in the production of concrete, which not only minimizes environmental issues but also provides economic benefits, especially in small countries such as Singapore with limited or almost zero sources of sand. The technical feasibility is conducted for three classes of concrete, i.e., C32/40, C40/50, and C50/60 produced with GF with varying fines content which is defined as the percentage of particle size finer than 62.5 μm (10%, 16%, and 22%) and percentage substitution (0%, 30%, 50%, 75%, and 100%). The technical feasibility of producing concrete with GF substitution is then evaluated based on performance comparisons between specimens with GF and NS (0% substitution) with regards to fresh concrete properties (workability through slump test, and setting time) and durability of hardened concrete properties (water absorption, water penetration, and rapid chlorine penetration).

Shunzhi Qian, Kang Hai Tan, Ziyang Li, Namyo Salim Lim, Lu Jinping, Wong Sook Fun
Effects of Various Ions in Seawater on Chloride Ion Behavior in Mortar Using Ground Granulated Blast-Furnace Slag

Concrete using ground granulated blast-furnace slag (GGBS) is said to have a greater effect on suppressing chloride penetration than concrete using only ordinary Portland cement (OPC). However, the chloride behavior and change of the pore structures in concrete using GGBS in the presence of various ions such as magnesium ions or sulfate ions in seawater have not been well investigated. This study aims to clarify the effects of various ions in seawater on chloride behavior in the mortar using GGBS. Two types of mortar were prepared with a water to binder ratio of 0.50. Only OPC and a mix of OPC and GGBS with a replacement ratio of 50% were used as binders. Crushed sand and tap water were used as fine aggregate and mixing water, respectively. After water curing of specimens at 20 ℃ for 28 days, an immersion test was conducted with four types of solutions for 28 or 56 days. The parameters for investigations in the immersion test were the total chloride content, the amount of Friedel’s salt measured with powder X-ray diffraction analysis, the porosity, and the pore size distribution. The results showed that the effect of various ions in seawater on the penetration of chloride ions was smaller for the mortar blended with GGBS than for the mortar using only OPC. In the chloride binding ability tests, regardless of the presence of various ions, the mortar blended with GGBS produced more Friedel’s salt than the mortar using only OPC. In addition, it was confirmed that the amount of Friedel’s salt in mortars using only OPC was reduced due to the influence of sulfate ions. Also, for the mortar using only OPC, the filling of hydrates into pores was observed after immersion in the solution with various ions, but only slightly for the mortar blended with GGBS.

Takuma Nakada, Yuko Ogawa, Kenji Kawai, Riya Catherine George

Advanced and Sustainable Concrete Materials

Carbonation of Granite Fines Concrete in the Tropical Environment

The exhaustion of major sources of natural sand in the region has provoked the use of alternative materials for sustainable concrete construction. Granite fines (GF) has been encouraged in many countries, including Singapore, to replace natural sand in concrete mixing. Carbonation is one of the most detrimental durability problems that cause the deterioration of reinforced concrete in the tropical countries like Singapore. However, the effect of GF replacement on the carbonation resistance of concrete is not well understood at present. The objective of the current work is to understand the effect of substituting natural sand with GF on the carbonation resistance of concrete in both accelerated and natural exposure condition. This study conducted a series of carbonation tests in both accelerated testing condition and natural exposure condition, on concrete produced with 0, 50, and 100% of granite fines substitution. The test results demonstrated that the replacement of natural sand with GF can enhance the carbonation resistance of the concrete. This study also established a correlation between the accelerated testing condition and natural exposure condition. The findings of this research provide recommendations on the service life design for industrial projects and may be further incorporated in design codes of the region.

Ni Zhen, Xudong Qian
Carbonation Resistance of Portland Blast Furnace Slag Cement Type B Concrete Internally Cured by Using Roof-Tile Waste Aggregate

Internal curing is a method in which a portion of the aggregate is replaced by a porous material having a high water absorption to supply curing water inside the concrete. The use of roof-tile waste aggregate as an internal curing material has been investigated, and its effect on reducing the autogenous shrinkage and increasing the compressive strength of ultra-high strength concrete has been reported. The purpose of this study was to evaluate the effects of roof-tile waste aggregate on the carbonation resistance of Portland blast furnace slag cement type B concrete. Six types of concrete with water-to-cement ratios of 0.50 and 0.35 were prepared with different replacement ratios of roof-tile waste coarse aggregates and fine aggregates. Concrete specimens were cured under sealed condition at 20 ℃ for 7 days before exposing to the air (20 ℃, 60%R.H.). The accelerated carbonation resistance, air permeability, and pore structure of concrete near the exposed surface were investigated. From the investigations, no densification of the pore structure by roof-tile waste aggregate was observed. It was found that roof-tile waste aggregate did not improve the carbonation resistance with a water-to-cement ratio of 0.50. When the water-to-cement ratio was 0.35, carbonation did not proceed enough to measure the carbonation depth and no difference was observed in the use of roof-tile waste aggregate. On the other hand, the use of roof-tile waste aggregate reduced permeability, regardless of the water-to-cement ratio. Therefore, the relationship between carbonation resistance and air permeability was different depending on the presence or absence of roof-tile waste aggregate. It is because the surface water content of concrete with roof-tile waste aggregate is higher than that without roof-tile waste aggregate, allowing more water to be stored inside the concrete and consequently increasing its impermeability.

Yusuke Inoue, Yuko Ogawa, Kenji Kawai, Riya Catherine George
Strength Characteristics of Blast-Furnace Cement Mortar with Silicate-Type Surface Penetrants

Concrete-using blast-furnace cement is more effective in increasing long-term strength, suppressing chloride-ion permeation, and alkali-silica reaction than ordinary cement. However, its strength development takes time, and it requires proper curing. In Japan, surface penetrants are used to maintain existing structures. In addition, the latent hydraulic property is promoted because the silicate-type surface penetrants are alkaline. The cover concrete becomes dense by reacting with the unreacted slag in the blast-furnace cement. The curing period can be shortened, and the quality of the cover concrete can be improved using this mechanism, leading to a new curing method. Therefore, in this study, we prepared a specimen in which 28 days old blast-furnace mortar was supplied with the amount of silicate-type surface penetrants used and an aqueous solution of calcium hydroxide as a reaction aid. We investigated its effect on strength characteristics.

Kei Futagami, Takuya Kondo, Katsunori Yokoi
Three-Dimensional Mesoscopic Modelling of Concrete Confined by FRP Under Static and Dynamic Loading

The strengthening of concrete materials has become one of the most important aspects in the design of any civil engineering structure, leading to a number of research to investigate and improve its mechanical behavior. The purpose of this study is to investigate the mechanical behavior of concrete confined with fiber reinforced polymer (FRP) under static and dynamic loading using a simple and thorough method. Two identical mesoscale concrete specimens and one FRP layer were created (concrete cylinder with a diameter of 50 mm, a depth of 100 mm, and the FRP layers with 1.27 mm of thickness) to compare the Finite element results to those of an existing experiment and a similar study previously conducted. The mechanical behavior of the simulated confined and unconfined concrete was compared to the mechanical behavior of an experiment with the same specimen size ratio. The localized phenomena in each element were considered in order to investigate the overall reaction of the created specimens, driven by the fact that concrete is a heterogeneous material made up of coarse particles, ITZ (Interfacial Transition Zone), and mortar. The parameters such as unconfined strength of concrete, maximum tensile, and maximum confinement stress are determined utilizing the confining pressure generated by the wrapped Fiber Reinforced Polymer on the three-dimensional mesoscopic concrete model based on the concrete-to-FRP confinement mechanism. From the findings of the investigation carried in this work, it is demonstrated that this study provides substantial insights into the question of strengthening and improving the mechanical behavior of concrete specimens subjected to static and dynamic loading.

Nyembo Ya Lumbu Lars, Jinhua Zhang

Seismic Resilient Structures

Development of Energy Dissipation Walls with Oil Dampers and Totally Reinforced Support Members Using Pre-stress

Many studies have been conducted on energy dissipation walls for small houses to improve the earthquake resistance of structures in Japan. Oil dampers, a main damper, is installed in studs to increase their strength. However, this method tends to deform each member and joint—“support members”—owing to tensile force, and therefore, the energy absorption performance of the damper tends to decrease. In this study, we propose an energy-dissipation wall that increases the overall stiffness by prestressing the support members to prevent tensile deformation. From 2020 to 2021, two types of specimens using laminated veneer lumber (LVL) as supporting members—Type 1 and Type 2—were tested to understand the mechanical behavior of the wall. Both types were subjected to static loading tests. Additionally, dynamic loading tests were applied to Type 2. Moreover, the dynamic behavior of the one-story wooden structure installed on the Type 1 wall was investigated by subjecting it to artificial earthquake waves. In state R which the damper part of the energy dissipation wall is restrained the load-deformation relationships obtained from the static loading tests for the two types of specimens using LVL as support members showed almost linear behavior up to the assumed damper load level for both specimens. In the dynamic loading test on Type 2, a stable load-deformation history with almost no slip was obtained. In shaking table test on Type 1, it was found that the energy dissipation wall incorporated into the wooden structure absorbed the energy of the artificial earthquake shaking and prevented the deterioration of its bearing capacity.

R. Sakamoto, K. Matsuda, S. Hanai
Comparative Numerical Study on Efficiency of Various Energy Dissipating Devices Used in Hybrid Post-tensioned Shear Wall

Conventional shear walls as a lateral-load resisting system have the disadvantage of getting damaged during severe earthquake shaking and can only be used after repair. This violates the philosophy of sustainable development, which is a critical aspect of the modern socio-economic scenario. To overcome this problem, shear walls are integrated with the post-tensioned (PT) tendons and are referred to as “PT shear walls.” Since the PT tendons remain elastic, the PT shear walls undergo rocking motion over the base and regain the original position after the seismic event; thus, the wall posses self–centering behaviour. Thus, they are reusable even after such events, and the downtime of the structure is minimal, thereby fulfilling the goal of resilient and sustainable development. However, the problem with the PT shear walls is that they have low energy dissipation capacity, owing to their elastic rocking behaviour. For energy dissipation, PT shear walls are fitted with additional energy dissipating devices and are known as “hybrid PT shear walls.” Conventionally the dissipating devices are placed internally, which solves the issue of low energy dissipation; however, it makes the shear wall weaker after an earthquake, and the replacement of dissipating devices is not possible. Therefore, recently the hybrid walls are fitted with dissipating devices externally, which provides good energy dissipation and the benefit of ease of replacement. Although several dissipating devices have been used in the past in various civil engineering applications, their suitability in hybrid PT shear walls is not available in the literature. Therefore, the present study aims at assessing the comparative response of these dissipating devices subjected to axial monotonic and cyclic loading through finite element (FE) analyses.

Shubham Tiwari, S. R. Dash, G. Mondal
Three-Dimensional FEM Simulation of Hysteretic Performance of Traditional Chinese Dou-Gong Connections

Dou-gong connection (complex bracket) is one of the typical wood-wood connections commonly used in traditional Chinese timber structures. The hysteretic performance of dou-gong connections is pertinent to the seismic performance of the traditional timber structures. Compared with experimental research, numerical simulation is more cost effective and not limited experimental techniques and thus is more versatile in study of hysteretic performance of dou-gong connections. In this paper, a three-dimensional finite element method(FEM) based analysis on hysteretic performance of single and double dou-gong connections was presented considering three dimensional elastic-plastic and damage constitutive model of wood. The results showed that the model prediction of the initial stiffness and lateral resistance of the connections agreed well with the test results in literature.

Xiaogang Zhang, Xiaobin Song, Jingliang Dong
Research on Seismic Behavior of CFT-Frame-Buckling Restrained Steel Plate Shear Wall Structures Using Recycled Aggregate Concrete

Several studies on steel plate shear walls (SPSWs) systems have revealed that the seismic demand on the vertical boundary elements (VBEs) is relatively high for ordinary structures. To resolve this problem and boost the application of concrete-filled steel tubes, two types of concrete-filled steel tubes (CFT) columns (square and L-shaped sections) for SPSWs, consisting of one span and two stories, were designed and tested under quasi-static load. Four corner and double sides connections welding form between frame elements and the shear wall were used to enhance the bearing capacity and stiffness. On the other hand, four corner and double sides fish plates were connected to the steel plate using high-strength bolts to improve the ductility and reduce the local buckling of the steel plate. In terms of buckling restrained, recycled aggregate concrete (RAC) and autoclaved lightweight concrete (ALC) were used as panels to minimize the buckling of steel plates. RAC was also used as a concrete infill. The specimens were evaluated based on hysteretic and skeleton curves. The bearing capacity and stiffness of both types VBEs using four-corner connections were enhanced while the double-sides connections improved the ductility of the SPSWs. Furthermore, connecting the frame elements by high-strength bolts improves the ductility but reduces the bearing capacity and stiffness compared with the welding ones. Finally, both RAC and ALC contributed almost the same buckling restraint in this study.

Amer Mohammed, Yansheng Du, Zhihua Chen, Jin Huang
Seismic Response Mitigation of Atrium Buildings with Truss-IMD System

In this paper, a novel truss-inertial mass damper (IMD) system is developed for seismic response mitigation of atrium buildings with an internal structure. An IMD with nonlinear damping characteristic is introduced to provide passive vibration control, and the unsynchronized dynamic response between the tops of the building and the structure inside the atrium is utilized to activate the IMD for energy dissipation purpose. Parametric studies are conducted to evaluate the effectiveness of the truss-IMD system on suppressing structural responses under earthquakes, with two performance indices set to reflect the response intensities in interstory drift and story absolute acceleration. Results indicate that for a preset IMD nonlinearity, there exists an optimal combination of inertance and damping coefficient to maximize a building performance for a given equivalent stiffness of the truss and internal structure. Results also show that the maximum achievable structural performance and the corresponding optimal IMD design parameters generally increase with increasing effective stiffness for a given velocity exponent. Multi-objective optimizations are also performed to further evaluate the capacity of the proposed system in reducing the interstory drift and story acceleration simultaneously using a 6-story building.

Siyuan Li, Yung-Tsang Chen
Seismic Performance of Isolated Liquid Storage Tanks Supplemented with Negative Stiffness and Inerter Based Dampers

Liquid storage tanks (LSTs) are lifeline structures that must stay operational during and after earthquakes. Their ability to withstand large earthquakes is a major worry. Although base-isolation protects LSTs from far-fault earthquakes, large-amplitude and long-period velocity pulses seen in near-fault earthquakes can generate substantial isolator and sloshing displacements, posing a problem. Supplemental damping in the isolation system may reduce isolator displacements, but the superstructure response may be hampered. To remove the drawback, this study presents novel combinations of negative stiffness dampers (NSDs) and inerter based dampers that utilise minimal dashpot co-efficient as supplemental dampers to base-isolated LSTs. The continuous liquid mass of the tank is modelled as lumped masses known as sloshing mass, impulsive mass and rigid mass. Based on the tank wall and liquid mass parameters, the stiffness constants associated with these lumped masses are calculated. The governing equations for isolated LSTs with proposed supplemental dampers are derived and represented in state-space form. Numerical studies show that combinations of optimally designed NSDs and inerter based dampers improve the performance of base-isolated LSTs in terms of isolator displacement, sloshing displacement and sloshing height under both near-fault and far-field ground motion.

Naqeeb Ul Islam, R. S. Jangid
Experimental Study on Seismic Behavior of Liquid Storage Tanks Subjected to Vertical Earthquakes

Previous studies on seismic performance of large-scale liquefied natural gas (LNG) storage tanks mainly focused on the horizontal earthquake excitations. However, vertical earthquake actions may lead to structural damage, overturning and even failure of a liquid storage tank, especially under near-fault earthquakes. In this study, aiming to investigate seismic behavior of the inner tank of a large-scale LNG storage tank subjected to vertical earthquakes, a shaking table test of a 1:25 scaled steel tank with full-filled liquid was carried out. Vertical components of El Centro waves, Chi-Chi 1529 waves and Chi-Chi 1505 waves were selected as input, representing near-field earthquakes, near-fault earthquakes without and with vertical velocity pulse, respectively. Seismic responses, including the sloshing wave height, hydrodynamic pressure and stress on the tank wall were obtained and analyzed. Results showed that the sloshing wave height under Chi-Chi waves was 1.2 ~ 2.5 times larger than that under El Centro waves. In comparison with El Centro waves with the peak ground acceleration (PGA) of 0.26 g, the peak hydrodynamic pressure increased by 10 and 36% under Chi-Chi 1529 waves and Chi-Chi 1505 waves, respectively. In addition, the vertical velocity pulse contained in near-fault earthquakes significantly amplified the stress on tank wall. For instance, the hoop and axial stress were increased by 269.12 and 63.50% at most under the excitations of Chi-Chi 1529 waves, respectively. Dynamic responses of liquid under vertical near-fault earthquakes were greater than that under near-field earthquakes, especially under the near-fault earthquakes with vertical velocity pulse.

J. Y. Wu, Q. Q. Yu, X. L. Gu

Resilience of Steel and Composite Structures

Axial Behavior and Design of High-Strength Rectangular Concrete-Filled Steel Tube Long Columns

Due to the lack of adequate research and deep understanding of high-strength concrete-filled steel tube (CFST) long columns, the current specifications cannot provide the available guidelines and design equations. To address the gap, this paper investigates the axial behavior of high-strength rectangular CFST long columns by experimental database, finite element analysis, and theoretical modeling. Firstly, the experimental database including 74 specimens for high-strength rectangular CFST long columns was compiled. Then, the detailed 3D non-linear finite element method (FEM) models were developed and verified for parametric studies. The effects of steel yield stress, concrete strength, section slenderness ratio and slenderness ratio on the ultimate strength and slenderness reduction factor were investigated. Finally, the possibility of extending the current design equations in different specifications was evaluated.

Zhichao Lai, Jie Yan, Dong Li
On the Accurate Strain Measurement in Split Hopkinson Tensile Bar Tests

The Split Hopkinson Tensile Bars (SHTB) are utilized to evaluate the dynamic material property under high strain rates. The one dimensional (1D) wave theory applies to determine the stress and strain of the test specimen. This study adopts the digital image correlation (DIC) technique to measure the full-field deformation along the specimen and compare the strain results with those collected from the strain gauges. The DIC-based strain results reveal nonhomogeneous specimen deformation under the dynamic conditions, and thus provide more accurate strain measurement to establish the stress-strain curve in the SHTB tests.

Cheng Chen, Xudong Qian
Adaptive Fatigue Assessment of Welded Plate Joints Based on Crack Measurements

Accurate fatigue assessment of welded plate joints remains critical for bridges, ships, offshore platforms, and steel structures subjected to cyclic environmental actions. Adaptive fatigue assessment of the structures incorporating with the crack measurement is essential for the digitalization process in civil engineering. This study conducts high-cycle fatigue tests of welded plate joints and proposes a new and enhanced constitutive damage model to simulate the fatigue damage. The constitutive damage model successfully predicts the fatigue life of welded plate joints under different levels of cyclic loadings. The remaining fatigue life of welded plate joints is updated through adsorbing periodic crack measurement information and achieves good agreement with the experimental results. The framework of this study lays the foundation in the digital twin of the local welded plate joints in offshore structures.

Liuyang Feng, Xudong Qian, Wei Zhang
Experimental Study on a Novel Sandwich Panel Under Repeated Impact Loads

Engineering structures may suffer repeated impacts from vehicles or falling objects during service life. Compared to traditional reinforced concrete structures, Steel-concrete-steel (SCS) sandwich composite fully uses the excellent tensile property of steel and compressive property of concrete. When subjected to impact, the steel plate can effectively prevent the impactor penetration, and the concrete core works as the energy dissipation layer, leading to excellent impact resistance of the sandwich structure. To further improve the impact performance, on the material side, the study adds rubber powder into the Ultra-Lightweight High-Ductility Cement Composite (ULHDCC) to develop the rubberized ULHDCC, i.e., RULHDCC; and on the structural side, the study utilizes hybrid shear connectors and double-layer sandwich. The study conducts an experimental program on the newly developed sandwich panels under repeated impact loads using the drop-hammer impact test machine. The failure modes, impact force responses, mid-span displacement responses, peak impact force, peak displacement and residual displacement are discussed in detail. The study also reveals the influences of the design parameters to the impact resistances of the sandwich panels, such as layer number, type of shear connector, spacing of shear connector, rubber content and impact number.

Wei Zhang, Zhenyu Huang

Smart Construction and Management

Readiness and Potential Application of Smart Contracts in the Indonesian Construction Industry

A construction project requires a contract to run safely by minimizing costs, schedules and maintaining project quality. In traditional contracts, contractual transactions between trustless parties are generally conducted in a centralized form, requiring a trusted third party to act as witnesses and make them legally binding, enforceable, and trustworthy. However, involving third parties is associated with high costs and delays. In this case, Smart Contracts can be a solution. A smart contract is a code that contains rules that will execute a transaction itself according to the agreement of two parties. Smart Contracts contained in Blockchain Technology have received much attention globally, including in the construction industry. Smart Contracts can enable automatic payments without delays, hassles and without third parties (mediators) carried out in a decentralized network to ensure integrity and transparency by preventing the potential of record manipulation existed in traditional contracts. This paper presents an overview of the potential application of Smart Contracts in Indonesian construction industry. This paper was prepared based on a literature review of several existing studies to obtain data related to the current state of Blockchain Technology, technological readiness, and the potential areas that Smart Contracts can be applied. It is hoped that the findings from the literature review will explain various aspects of the potential for adopting Smart Contracts in the construction industry and can assist in the development of further research that will focus on the application of Smart Contracts in the Indonesian construction industry.

Kartika Wulandary, Kriengsak Panuwatwanich, Michael Henry
Construction Process Simulation Facing Digital Twin

With the development of digitization, informatization, and intelligence in the field of civil engineering, a large amount of data has been accumulated during the construction process, forming engineering big data. How to effectively analyze the construction process by mining the relationship between these data to improve the management efficiency will be an important research direction. Graphs have natural advantages in describing complex association relationships between data and are widely used in the analysis and mining of association relationships. Therefore, this paper will make full use of the relationship between construction data based on the graph database to establish a process simulation framework facing digital twin. This framework consists of three parts. Firstly, data collection from BIM models, surveillance videos, and IoT networks is stored in a graph database. Secondly, the graph database will be imported into a discrete event simulation model to automatedly simulate the future construction process with the results written back to the graph database. This DES model will make full use of this data and its relationships to obtain a more reasonable result. Process information obtained from this DES, such as schedule information, resource information, cost information, will be directly connected to the components. Thirdly, the as-planned process, as-built construction process, and graph database-based process analysis results will be dynamically displayed on the digital twin model to support real-time decision-making. A case study is demonstrated to verify the proposed framework’s validity and feasibility.

M. S. Dong, B. Yang, Y. L. Han, S. S. Jiang, B. D. Liu
Establishment and Application of Multi-agent Simulation System Based on On-Site Construction Performers

Despite the literature on multiple decision agents in the construction process, questions regarding the on-site behaviour of construction performers and their interaction with the site remain unanswered. The study aims to simulate the construction process based on the behaviours of on-site construction performers. It first establishes a multi-dimensional simulation environment that includes construction procedures, work plane and component states. Then the Spatio-temporal attributes of the construction performs are encapsulated into the agents. And last, the interaction mechanism between the agents and the simulation environment is defined, that forming a multi-agent-based simulation system for the construction process. The proposed system is developed using Python code, which can be applied to simulate short-term construction process with agents modeling, environment modeling and agents’ strategies et al. information imported, and a real case study is carried out through this way. The case study shows that the result of the established system has passed the verification of the traditional discrete event simulation result. And a construction strategy testing proves that this system can help managers to test and quantify the impact of different construction strategies so as to choose the most effective one to execute.

B. D. Liu, B. Yang, Yilong Han, J. Z. Xiao, M. S. Dong
Digital Fabrication for DfMA of a Prefabricated Bridge Pier

Many countries have a strategy to increase the ratio of off-site construction. Design for manufacturing and assembly (DfMA) is a challenging requirement for a designer in the construction industry. Prefabricated structural members are widely utilized for bridge construction to minimize on-site activities. This paper proposes digital fabrication models for DfMA considering 3D concrete printing and CNC milling. Data-driven information delivery between the digital model and the robot arm was defined. Prefabricated bridge columns require strict geometry control, especially for match casting. Design for assembly procedure through digital models and robotic technology is proposed. Digital fabrication is essential for a fully prefabricated bridge. Consequently, a printed permanent formwork has been applied for a novel digital fabrication method of the prefabricated column segments.

T. K. Kim, D. C. Nguyen, C. S. Shim
Study on the Open Data System for Infrastructure Maintenance and Management

In Japan, periodic inspection of social infrastructure is compulsory every five years. Consequently, after infrastructure inspection, many valuable data sets are accumulated. In Yamaguchi Prefecture, however, data are managed using an Excel file format. This makes it difficult and inefficient to extract information from data. Also, incorrect data input can occurs, because data are input manually by a person. In response to this problem, the authors developed a data extraction and conversion system. Which extracts a specific range of Excel format data and converts it to JSON format, making it easier to utilize information by correlating data based on bridge inspection data. By using such a data modification system with Google Map, incorrect data can be identified and corrected. Furthermore, an open data Web API system structure was developed, for future visualizations and analysis. The paper will conclude the authors assessment of the performance of those systems as well as their thoughts on the future utilization of bridge inspection data.

Junha Hwang, Kei Kawamura, Shuji Sawamura
Road Development Risks and Challenges in the Philippines

The Philippines, as a fast-growing country, has had the highest road infrastructure investment to date for the past five years compared to the previous years. The infrastructure programs of the government as a solution to decongest Metro Manila and develop the countryside for economic growth are promising yet result in various risks and challenges. This research presents the road development issues from multiple sources; primary data from interviews of stakeholders of road development, secondary data from online news articles, social network services, government issuance, policies, and related literature. The Philippines is in a dire economic situation due to the Covid-19 outbreak that resulted in the country’s worst economic performance since the Asian financial crisis in 1998. The country’s economic managers pinned high hopes on the government infrastructure programs as a vital strategy to help pump-prime the economy towards recovery due to its job generation and multiplier effects. Hence, it implicates enormous risks and challenges such as low tax revenues, the trade-off with more urgent Covid-19 response measures, foreign and private companies support, unsolicited project proposals, inequitable distribution of infrastructures, and delays in construction activities. Various road development stakeholders also mentioned the need for strict road regulations, urban and regional planning, aesthetic improvement, urban renewal in aid of car-centric infrastructures, and routine maintenance on-road sections. The data are structured in various categories such as public involvement, environmental preservation, public policy, project planning, road design, road safety, economic recovery, and construction time. Lastly, the implications for future research directions are discussed.

Kenneth Edward Torrella Fernando, Michael Henry

Teaching and Learning During and After Pandemic

Understanding Sustainability Practices Through Sustainability Reports and Its Impact on Organizational Financial Performance

Beyond publishing annual reports, which document organizational activities and their financial performance, organizations are increasingly publishing sustainability reports to inform stakeholders and the public about their sustainability practices. This raises the question as to whether there is a correlation between sustainability practices and financial performance. However, sustainability reports contain huge bodies of text, and much time is required to analyze the content manually. Hence, text mining was employed in this study, by which the top-ten sustainability-related words in the sustainability reports were identified. Subsequently, these ten words were mapped to 5 UN SDGs: (1) Goal 3: Good health and well-being, (2) Goal 8: Decent work and economic growth, (3) Goal 9: Industry, innovation, and infrastructure, (4) Goal 12: Responsible consumption and production, and (5) Goal 13: Climate action, which were categorized into three themes: (1) Social (Goal 3), (2) Economic (Goal 8 and 9), and (3) Environment (Goal 12 and 13). The relationship between organizational sustainability performance and financial performance was subsequently examined with correlation analyses. The results revealed that organizations with higher FTSE Russell ESG ratings had higher GTI scores, which indicates higher transparency in their reporting. Organizations with higher FTSE Russell ESG ratings also had lower net profits, although the average net profit for these organizations was positive. Furthermore, no statistically significant relationship between FTSE Russell ESG and ROE was found. These findings suggest that ESG-rated organizations are still profitable, and that there is value in investing in ESG-rated organizations. Findings from this study provide an overview of the sustainability practices that local organizations are practicing, and could serve as a reference for other organizations to move towards a green economy.

Mavian Xin Yi Tay, Stephen En Rong Tay
Broadening the Perspective of the Roles of Civil Engineers – A Freshmen Module on How Engineers Solve Real-World Problems

Taking the role of a team of civil engineers, students working in a group of five prepare a bid for a civil infrastructural project for the government to address a pressing need in society. Students were guided using a framework where they identify, define, set goals, generate solutions, and evaluate alternatives from the financial, economic, environmental and society perspectives. This Year 1 module was conducted using a flipped classroom approach in the second semester over a 13-week period. A different theme could be assigned for every new semester and the theme of “Designing Infrastructural Solutions to Tackle the Effects of Climate Change” was adopted for the most recent run of the module to reflect the current interest on this topic. This paper will outline the philosophy behind the development of this module and other details including the format and learning support provided for students, student activities and deliverables, assessment and student feedback. A discussion of the main lessons learnt and some recommendations for future adoption of this learning approach in a civil engineering programme will also be presented.

Kevin Sze Chiang Kuang, Weng Tat Chan
SafeSim Design: A Digital Game-Based Learning Approach to Address Design for Safety (DfS) Competency

The Singapore government enacted the Workplace Safety and Health (Design for Safety) Regulations in 2015. However, the construction industry continues to be the nation’s main contributor to workplace injuries. As such, there is a need to develop competency in Design for Safety (DfS) within the industry so that designers (i.e., engineers and architects) can anticipate and “design out” construction, maintenance, and demolition hazards and risks. One way to improve the DfS competency of designers is through digital game-based learning (DGBL), a research-based educational approach developed to motivate and engage learners through interactive gameplay. Thus, this study developed SafeSim Design (SSD), a single-player digital game, to educate designers on the difference between design risks and occupational hazards, conduct risk evaluation, and design out risks through various design-related controls. SSD incorporated different game design elements that could effectively support the learning needs of designers. In addition, the game content is a collective effort from the authors and industry professionals in collating design-related case studies, ensuring fidelity and authenticity. This paper presents the development process of SSD, including the different game design elements and the incorporation of specific teaching strategies. The study also demonstrates how SSD can be an effective teaching tool for professional development (PD). Future studies will include an experimental study to evaluate the effectiveness of DGBL as an instructional tool in the context of the Built Environment.

Sufiana Safiena, Juliana Tay, Yang Miang Goh, Michelle Lim
Identification of Critical Factors Influencing Students’ Engagement and Satisfaction of Online Live Learning in Higher Education

In response to the COVID-19 epidemic, online live teaching becomes the main teaching method rather than a choice. Considering the immediate habit change in education, this study aims to identify the critical factors influencing students’ engagement and satisfaction with the online live courses using a structural equation model and an online questionnaire survey. Through a comprehensive literature review, four critical factors influencing students’ engagement and satisfaction which are instructor behaviors, student characteristics, course organization, the state of health, wellbeing, and sense of community-related (HWC) issues were identified and their relationships as well as measurement indicators for each factor were proposed. Through a survey, 306 valid responses were collected from civil engineering students in China in 2020. The results showed that instructor behaviors and student characteristics have the highest impact on student engagement and perceived learning, respectively. Moreover, the mediating effects of student engagement between instructor behaviors and student characteristics and perceived learning and satisfaction are statistically significant. Furthermore, the state of HWC issues caused by intensive online learning does have a significant negative impact on student satisfaction. Besides, the relative importance of practices affecting student online learning effects was prioritized. The findings contribute to the body of knowledge of online teaching theories and strategies. Moreover, the instructor and the education manager can improve their online live arrangement by referencing the findings of this study.

Lei Zhu, Lina Zhang, Guifeng Zhu
Preliminary Implementation of Adaptive Learning for Teaching Structural Systems to Non-engineering Students

The pandemic has caused a drastic shift to online teaching and learning. However, online teaching and learning still face similar problems to traditional teaching and learning, and one example is the “one-size-fits-all” approach. The ineffectiveness of such an approach is particularly pronounced in interdisciplinary teaching and learning. For example, non-engineering students entering engineering-related courses (e.g., engineering project management and facilities management) have diverse math, physics, and chemistry knowledge backgrounds. Correspondingly, students face different challenges in obtaining the necessary background knowledge for engineering-related courses. One solution to overcome the challenges is adaptive learning, an intelligent approach to providing personalised educational paths for each learner to learn more effectively and efficiently. This study proposes a preliminary framework for implementing adaptive learning for teaching structural systems, a subject in structural engineering, to students with diverse backgrounds. The framework consists of five modules: adaptation, content, learners, instructors, and feedback. The paper discusses a case study of a Structural Systems course for non-engineering students, which utilised the framework to implement adaptive learning in 2021. Preliminary findings show that students are generally satisfied with the adaptive learning approach. Furthermore, the preliminary framework can be adapted and applied to other interdisciplinary teaching and learning settings.

Xinping Hu, Yang Miang Goh, Alexander Lin, Qizhang Liu

Resilient Infrastructural Solutions

Analysis of the Clearance Time of Roadblock Events Caused by Geohazards in Bhutan

The importance of providing precise Real Time Information (RTI) to road users has become one of the key roles for the concerned government agencies in Bhutan to ensure the safety of road commuters and also regulate the smooth flow of goods and people in the country. However, to date, the essence of RTI is usually compromised, owing to several unforeseen factors and a lack of sufficient resources at the site. Thus, this research studied and analyzed factors governing the clearance time of roadblock events caused by road geohazard such as landslide, rockfall, flood, etc. Statistical and Geospatial analyses were carried out on the roadblock data (2020) obtained from the Department of Roads. A Theissen Polygon technique in the GIS platform was constructed to obtain the rainfall intensity that was recorded during and after roadblock clearance time. Locations of pre-deployed machinery were also included to investigate the relationship between these two variables and the clearance time. Overall, it took an average of 12.2 h to clear the roadblocks that were recorded, with the longest and shortest times recorded in the Phuentsholing and Trongsa region, i.e., 360.2 h and 0.2 h, respectively. Concurrently, the locations that took the longest were those that did not have machinery on-site. The average time for clearing a block with and without machinery was 10.4 h and 13 h, respectively. Concerning the rainfall data, the clearance time was directly proportional to the accumulated rainfall intensity from the occurrence time to the clearance time. Thus, knowing such relationships and patterns can assist agencies in prioritizing locations and allocating necessary resources, as well as improving the predictability of tentative clearance times to reduce errors in sharing RTI with commuters so that they are not misinformed.

Dhan Raj Chhetri, Michael Henry
Research on Cumulative Plastic Deformation of the Soft Clay Under Cyclic Loading

In coastal areas, the cumulative plastic strain development characteristics of soft clay foundation of wharf, airport, highway, etc., will change under long-term loads. In order to reveal the influence of the consolidation state and the drainage conditions on the cumulative plastic deformation of soft clay, a series of dynamic triaxial tests were carried out by the GDS triaxial apparatus, and then the cumulative plastic deformation of clay was analyzed and studied based on the fractional partial differential theory model. The test results show that the cyclic strain amplitude of drained triaxial test decreases with the increase of confining pressure, the base value creep curve decreases, and the cyclic strain amplitude also decreases; With the increase of vibration times, the hysteretic curve moves to the right and quickly tends to be dense. A certain amount of plastic strain will be accumulated in each loading cycle, but the accumulation decreases gradually. The plastic strain tends to be stable, and the elastic properties of soil become more prominent. Under different drainage conditions, the undrained cyclic strain curve is less than the drained cyclic strain curve, but the cyclic strain amplitude of the undrained cyclic strain curve is greater than that of the drained cyclic strain curve.

Xubing Xu, Zhendong Cui, Yonglai Zheng
Improved Vehicle Scanning Method for Bridge Damage Detection

In this paper, the bridge damage is detected by improved vehicle scanning method. In order to extract the narrowband signals from the vehicle response, the improved VSM uses a designed elliptic filter. These narrowband signals generally have a good signal-to-noise ratio. Therefore, the signals can reconstruct vibration modes accurately. For a damaged bridge, the kinks on the vibration modes reveal the damage locations. It has been found this improved VSM yields a better result with a series of vehicles passing over the bridge. In addition, the reconstructed mode shapes reveal a more noticeable kink. It can be used to point out the damage location when compared to the use of existing VSMs. As a result, the improved VSM can distinguish the damage locations directly with little to none post-process. This is unlike the other VSMs generally need to compare baseline model, construct damage index, etc. to determine the damage.

D. S. Yang, C. M. Wang, W. H. Duan
Positioning Accuracy Comparison of RTK Receivers Used for Disaster Investigation

In recent years, heavy rains that cause great deal of human damage have occurred in the northern Kyushu and the Chugoku regions, and severe sediment-related disasters have been caused. In the event of sediment-related disasters, a prompt survey is required to prevent the spread of damage. Therefore, the authors have developed a disaster investigation support system that aims to enhance the safety of investigators and their work efficiency by using a multi-band receiver. In this paper, the fixed-point positioning accuracy of some RTK receivers was evaluated at the disaster recovery site in Hiroshima Prefecture, where the sediment disaster surveys were actually conducted. In experiments on sabo dam aimed at confirming fixed-point positioning accuracy in a poor radio environment, it has been confirmed that the variation in horizontal positioning results is 22 mm (2DRMS) or less. Our experiments for the positioning performance in the forest have shown the variation in the horizontal positioning results being 0.65 m or less (2DRMS).

Toru Yamano, Kai Kiriyama, Osamu Okamoto, Kei Kawamura
Corrosive Behavior of Structural Steel and Hot Dipped Galvanized Steel in the Central Part of Thailand by Atmospheric Exposure Test

Central part of Thailand consists of several kinds of areas like metropolitan area and non-packed area. Those kinds of characteristics could cause different corrosion rates based on the atmospheric conditions and environmental pollutions. In this paper, atmospheric exposure test study with six test locations for bare steel and hot dipped galvanized steel is illustrated. The chosen test locations conformed to ASTM G50 standard. Environment parameters have been collected at the test locations. The meteorological data from the governmental website has also been collected to complete the gap. After exposure, the specimens have been collected and analyzed based on ASTM and ISO standards. This study result shows the thickness loss for bare steel and hot dipped galvanized steel at each test location and how important and effective the galvanized coating is in the test locations.

Bunya Chea, Taweep Chaisomphob, Takashi Matsumoto

High Performance Materials and Structures

Experimental Investigation of Circular Reinforced Concrete Columns Exposed to Elevated Temperatures

This paper presents an experimental study on thermal and structural performance of fire-damaged circular reinforced concrete (RC) columns with medium and high strength concretes. A total twelve circular RC columns were exposed to elevated temperatures following the ISO 834 standard fire curves up to 120 min. The investigation focused on the effect of concrete compressive strength and fire duration on the residual axial capacity. The paper presents the temperature radiation into the column’s section versus duration and exterior temperature levels. In addition, detailed deterioration damage of the columns, residual axial load carrying capacity and load-displacement response of columns are presented. Detailed review of experimental work done by others is also presented.

Jia Xu, Riyad Aboutaha
Mechanical Model for Parallel-to-Grain Withdrawal Failure of Self-tapping Screws in Glulam

In response to the goal of carbon neutrality under the background of global climate crisis, timber as a kind of bio-based material regains a new attention in the field of building. When the building industry hopes to promote timber structure in practice, existing connection techniques are in urgent need of innovation. Currently the improving screw manufacturing process can supply the threaded fasteners such as self-tapping screw or threaded rod with sufficient lengths and optimized threads to the market, which provides a promising technical solution to realize the strong and stiff timber connections. Distinguished from the common laterally-loaded metal fasteners such as dowel and bolt, the self-tapping screw can be regarded as a kind of fastener capable of load transfer along the direction of its axis. Before the application of this axially-loaded threaded fastener in timber connection, the withdrawal failure mechanism of self-tapping screw in wood should be researched in depth to avoid the withdrawal failure at first. Different from existing models based on the classical theory of Volkersen, a new mechanical model for parallel-to-grain withdrawal failure of self-tapping screws in glulam is proposed in this paper. “Assembly unit”, which can be assembled to the whole fastener surrounded with failure wood and disassembled to some discrete parts, is first introduced as a mechanics analysis unit in this model to research the withdrawal failure of self-tapping screws in glulam and calculate the anchorage length of self-tapping screws in glulam. The model considers the distinctive mechanical behaviors caused by the thread of the screw: the local stress of wood filled in the screw pitch and the discontinuous transfer of shear stress/force on the failure surface. The theoretical calculations achieve an acceptable agreement with the results of two experimental investigations, and the reasons affecting the accuracy of the model are discussed for further improvement.

Lijing Fang, Wenjun Qu, Shengdong Zhang
Behaviors of Steel-Concrete Composite Structures at Cold-Region Low Temperatures

This paper delivers the recent research progress on steel-concrete composite structures at cold-region low temperatures, which aims on the engineering constructions in the Arctic/cold regions. This paper summarizes the recent research progress of the authors on the ultimate strength behavior of steel-concrete composite structural members at low temperatures. The paper firstly reported the research progress on the low-temperature mechanical properties of constructional materials in the CFSTs that included mild steel and high strength steel Q690. Secondly, the steel-concrete bonding behaviors of CFSTs at low temperature were also studied through full-scale tests. Thirdly, the axial low-temperature compression behavior of CFSTs using mild steel tubes and NWC were experimentally studied. Finally, the ultimate strength behavior of steel-concretes-steel (SCS) sandwich composite beams at cold-region low temperatures. The influences of different parameters on low-temperature ultimate strength behaviors of SCS sandwich composite beams were discussed and analyzed. All these studies built the foundations and clear the obstacles of application of steel and composite structures used in the Arctic and cold regions with low-temperature environments.

Jia-Bao Yan, Jian Xie
Development of Novel Sigma-shaped Self-locking Inter-modular Joints for Robust Modular Steel Buildings

Modular Steel Buildings (MSBs) are a new structure consisting of fully assembled volumetric units. The inter-modular connections are essential components contributing to MSB’s onsite assembly and structural safety. It is necessary to have a precise and valuable intermodular joining system that allows for efficient load transfer, safe handling, and the most efficient use of the modular components’ strength. The majority of inter-module connections are currently manual vertical column-to-column welded, bolted, or prestressed, which has a lot of shortcomings, including poor quality, inefficient construction, lack of space, full connectivity, and incompatibilities with interior design. Moreover, due to a discontinuous horizontal diaphragm and vertical walls, the lack of horizontal and vertical beam-to-beam connections between modular units reduces in-plane and out-of-plane stiffness and uniform lateral force transmission. To overcome the concerns mentioned above, this study first presents a unique self-locking automatic vertical column-to-column inter-modular connection that uses connection boxes with spring-loaded tenons and mortises with tongues and grooves to achieve vertical connectivity. Then, to guarantee horizontal diaphragm continuity, a horizontal beam-to-beam interlocking connection with a continuous group of interlocking clips with sigma-shaped tongues and grooves is proposed, welded on modular floor beams. Then, a vertical beam-to-beam interlocking connection with a group of interlocking clips is developed, welded on beams offsite to achieve vertical diaphragm continuity. The proposed vertical and horizontal connections satisfy simple splicing, non-welding, easy installation, complete and robust connectivity, and reliable connection characteristics. Furthermore, finite element analysis revealed that developed connections enhance in-plane rigidity and improve MSB vertical and horizontal connectivity, maximizing modular building assembly benefits.

Kashan Khan, Zhihua Chen, Xingwang Liu, Jia-Bao Yan, Jiadi Liu
Shear Performance of Interface Between Normal Concrete and Ultra-high Performance Concrete in Cryogenic Circumstance

Ultra-high performance concrete(UHPC) is known for its high strength, high toughness and durability, which makes UHPC be seen as a promising repairing material for normal concrete(NC). In order to make sure the application of UHPC in reinforcement, especially in cryogenic circumstance, it is critical to characterize the bonding performance between UHPC and NC. Through 11 sets of normal concrete and ultra-high performance concrete specimens (UHPC-NC specimens) were tested by double shear tests, the shear properties of UHPC-NC specimens in normal and cryogenic environment (−60 °C) were evaluated and discussed. Different interface treatments were used, including untreated, water jetting and using retarder. The effect of interface agent was also studied. The results show that the shear strength of the interface was improved by increasing surface roughness degree. The failure mode presented brittle failure, no matter what kind of interface treatments. Cryogenic circumstance can improve the bonding strength of UHPC-NC, and the group without interfacial agent had a more significant improvement. The performance of interfacial agent in low temperature limits the improvement of interfacial bonding strength to a certain extent.

Yujie Chen, Jian Xie, Ercong Kang, Chenglong Tong
Effects of Arctic Low Temperatures and Freeze-Thaw Cycles on Mechanical Properties of Ultra-high Performance Concrete

Ultra-high performance concrete (UHPC) has a significant advantage in complex structures relevant to Arctic environment conditions such as long-span bridges and offshore platforms due to its high strength, high toughness and excellent durability. To explore the compressive response of UHPC at low temperatures and after freeze-thaw cycles, two series tests were conducted. Firstly, the compressive strength of UHPC exposed to low temperatures was experimentally investigated. The UHPC cubes had good integrity after failure due to the bridging effect of continuous steel fibers. The compressive strength of UHPC increased almost linearly with reducing temperature in the range of 20–80 ℃. Then, a total of 17 groups of UHPC and NWC cubes were prepared to explore the compressive response of UHPC after freeze-thaw cycles. The investigated parameters include freezing temperature (−30, −60, and −80 ℃) and number of freeze-thaw cycles (25, 50, 75, and 100). With the increase of number of freeze-thaw cycles and the decrease of freezing temperature, the degradation in compressive strength of UHPC gradually became distinguished. Finally, the regression analysis was conducted to establish the empirical formulae for the compressive strength of UHPC at different low temperatures and after freeze-thaw cycles. The accuracy of the developed formulae was validated by the experimental results.

Ercong Kang, Jian Xie, Jiabao Yan, Jing Tang
Compressive Behavior of High Strength Steel Wire-Mesh Reinforced Concrete Filled Steel Tubular Columns

Square steel tube cannot provide effective confinement to core concrete in a concrete filled steel tubular (CFST) column, in this regard, the transversely-placed high-strength steel wire mesh (SWM) is proposed to enhance such confinement. The enhancement mechanism of SWM is rather different from traditional CFST columns where the confinement is provided from inside of core concrete through the interactions between SWM and surrounding concrete, such confinement reduces the dilation of concrete. The compressive behavior of high strength SWM reinforced square CFST columns were investigated experimentally, it is found the load-carrying capacity of square CFST columns can be largely improved.

Fangyuan Gao, Mingxiang Xiong, Fengming Ren

Prefabricated Construction and Composite Structures

Numerical Study on Out-of-Plane Mechanical Performance of New Type Precast Shear Wall with Unspliced Vertical Distribution Bars

To eliminate the shortcomings in the grouting sleeve in precast shear wall structure induced by the poor grouting, difficult quality assurance and low construction efficiency, a new type of precast shear wall structure with unspliced vertical distributed bars (SGBL precast shear wall) was proposed. In this paper, a numerical study was carried out to preliminary explore the out-of-plane mechanical performance of SGBL precast shear wall based on the verified finite element simulation method. The influence of different parameters on the out-of-plane mechanical performance of SGBL precast shear wall was investigated by FE analysis. The results show: 1. The out-of-plane mechanical performance of SGBL shear wall is similar to that of cast-in-situ shear wall; 2. The axial compression ratio is the key factor of out-of-plane mechanical performance of shear wall and increase of wall thickness can significantly improve the out-of-plane bearing capacity. Finally, several engineering suggestions were proposed to control the out-of-plane safety of SGBL precast shear wall.

Qiang Fu, Zhiwei Cao, Heng Dong
Lightweight and Advance Precast Concrete System for Modular Building Construction

Productivity and efficiency are the critical aspects emphasised by the present Singapore construction industry, and these demands are addressed from two key approaches: construction materials and methods. These aspects involve the intensive coordination amongst various stakeholders in construction, prompting a need to collaborate and utilise highly intricate technologies such as Design for Manufacturing and Assembly (DfMA) in Advanced Precast Concrete System (APCS) and Prefabricated Pre-Finished Volumetric Construction (PPVC). DfMA is a systematic quality control method of construction that is vital to Singapore’s Construction Industry Transformation Map. PPVC system taps on the 3-dimensional modular production technology, fabricating modules off-site, and later installed on-site. However, the limitation for incorporating Concrete PPVC in Healthcare and Institutional buildings lies in the mismatch between PPVC module dimensions and the predominant design philosophy of the flat slab system. Thus, there is a need for a more flexible PPVC construction methodology to allow the construction to tap on the benefits of DfMA. The proposed Large Panel System (LPS) is used in conjunction with Concrete PPVC to overcome the rigidity in the design and construction of healthcare and institutional buildings. In the present study, a typical cast-in-situ Lightweight Concrete (LWC) building and a PPVC-LPS Hybrid LWC building are modelled and analysed using a 3D Non-linear Structural Finite Element software. Both buildings are designed based on various design limit states from the Eurocode 2 (EC2) section of Structural Lightweight Aggregate Concrete (LWAC), and their performances are compared. This paper aims to study the viability of the PPVC-LPS Hybrid LWC construction for healthcare and institutional buildings. Compared to the conventional cast-in-situ method, the innovative hybrid construction is found to be more superior due to its rapid connection method, meeting the structural integrity performance of cast-in-situ buildings.

Junxuan Wang, Kian Hau Kong, J. Y. Richard Liew
Study of Initial Imperfection of Concrete-Filled Square Steel Tube Columns for Direct Analysis

The initial imperfection and residual stress play important roles in the buckling resistance of both structural system and structural members. The latest Standard for Design of Steel Structures (GB50017-2017) firstly introduces the direct analysis method for the stability design of steel structures in China. The equivalent initial imperfections for steel members have been well specified in this code. However, as an important part of modern structures, there is limited research on the initial imperfections of steel-concrete composite members in relevant regulations in China. Therefore, it is urgent to study the equivalent initial imperfections of steel-concrete members for direct analysis. This paper collects extensive experimental data on concrete-filled square steel tube columns (CFSSTC) for calibration of finite element models using software ABAQUS. The key factors affecting CFSSTC’s behaviors such as section dimensions, grades of steel and concrete, and width-to-thickness ratios have been taken into account. A comparative analysis for the CFSSTC with and without initial imperfections will be presented. From this study, the equivalent initial imperfection for CFSSTCs will be proposed for practical direct analysis of steel-concrete composite structures to achieve a safer and economical design without use of conventional effective length method.

Zijuan Zhang, Jiale Xing, Yao-Peng Liu, Guochang Li
Nonlinear Coupled Thermal-Structural Analysis of Monolithic and Precast Concrete Corbel Beam-to-Column Connection

In this paper, a nonlinear coupled thermal-structural analysis is executed using ANSYS Workbench to simulate the fire performance of monolithic and precast concrete corbel beam-to-column connection at high temperatures. The monolithic models, namely M22-S and M600-S, represent the testing temperatures of 22 ℃ and 600 ℃. The precast concrete corbel models, namely C22-S and C400-S, represent the testing temperatures of 22 ℃ and 400 ℃. The models are simulated to failure under incremental point loads at the end of the beam that produced hogging moments to the connections. The response of the models is validated against the load-deflection curves and toughness of connections from the previous experimental test. The relative connection performance at ambient and high temperatures is evaluated and discussed. The load-deflection curves for connections M22, M600, and C22 show a good agreement between the simulation and experimental results. The load-deflection curves are reduced with increasing temperatures. The toughness for connections M22, M600, and C22 (simulation and experimental) has verified the accuracy and applicability of the proposed simulation model. The toughness results show that the connection at ambient temperature (M22 and C22) has higher fracture resistance than at high temperatures (M600 and C400). The validation result of nonlinear coupled thermal-structural analysis executed using ANSYS Workbench gives good efficiency for predicting the fire performance of monolithic and precast concrete corbel beam-to-column connection at high temperatures.

Noor Azim Mohd. Radzi, Shanmugam Muniandy, Fadlin Sakina Ismasafie, Roszilah Hamid
Mechanical Performance of Novel UHPFRC Grouted SHS Tube-Sleeve Connection: Experiments, Numerical Simulation and Analytical Approaches

This paper presents the axial and lateral performance of a novel ultrahigh-performance fiber-reinforced concrete (UHPFRC) grouted SHS tube-Sleeve connection for prefabricated prefinished volumetric constructions (PPVC). The experimental study tested 18 full-scale specimens with varying shear key spacings, inner tube lengths, inner tube heights, and volume proportions of steel fiber in UHPFRC. The results showed that the connection have adequate resistance and ductility to resist tension and bending moment. The failure modes in tension mainly include the shear failure of the UHPFRC and the fracture of the inner tube, while the failure modes in bending mainly include the fracture of the inner tube and the slip of the grout. To further understand the load transfer mechanism of the connection, the advanced finite-element (FE) models were built to simulate the axial and lateral load–displacement behavior, strain and crack development of the grout. Thereafter, new design formulas are developed and evaluated to predict the axial and lateral resistance of the grouted connections. Validation against the test results showed that the new formulas can provide reasonably effective and accurate predictions of the axial-load and lateral-load resistance of the novel grouted connection.

Zhenyu Huang, Weixiong Deng
Effects of Gap Arrangement on the Compression Behavior of Square Tubed Steel Reinforced-Concrete Columns

For a tubed concrete column, generally, the tube gaps are arranged at column ends to avoid the steel tube carrying loads directly. This paper experimentally and numerically investigated the behavior of square tubed steel reinforced concrete (TSRC) columns with an additional gap at the mid-height of the steel tube. Four square intermediate TSRC columns were tested under axial and eccentric compression, and the main test parameters were the load eccentricity ratio and width-to-thickness ratio of steel tube. The failure modes and ultimate strength were analyzed. The test results demonstrated that the columns with two types of gap arrangement schemes showed similar failure modes. The axial compression strength of the column with an additional gap at mid-height was slightly higher than that of the column with gaps at the column ends, while the eccentric compression strength of column showed the opposite result. A detailed finite element (FE) model was developed and verified, in which the material nonlinearity and initial geometric imperfection were considered. Further parametric analysis was carried out based on the verified FE model.

Biao Yan, Quanlin Zhou, Dan Gan
A Modified Beam-to-Column Connection for Steel Modular Structures with Enhanced Repairability

This paper presents an investigation on the static strength of a modified beam-to-column connection in steel modular structures. The modified beam-to-column connection aims to enhance the repairability of the connection after an extreme loading condition. The onsite installation of the connection entails only bolt connections with the welding procedure completed in the pre-fabrication procedure in a factory. The current study examines the static strength of the beam-to-column connection under static loading conditions, and confirms that the proposed connection demonstrates sufficient moment resistance under static conditions. The parametric investigation examines three different effects on the moment resistance of the proposed connection scheme.

Jiajia Xu, Xudong Qian, Chengguang Xu, Ran Tao
Numerical Analysis of Precast Shear Wall with Opening and Unspliced Vertical Distribution Bars

To investigate the effect of opening on the lateral behaviour of precast concrete shear wall with unspliced vertical distribution bars, a series of nonlinear numerical analyses is carried out. Cohesive elements and nonlinear springs are adopted to simulate the joints around the precast wall panel and the steel bars across the joints, respectively. The numerical analysis model was verified based on test results of the lateral behaviour of precast shear wall with unspliced vertical distribution bars. Based on the verified model, parametric studies are carried out for the influence of the opening’s characteristic parameters and the length of the boundary element. The results show that the influence of the area ratio and location of the opening on the lateral behaviour of the precast shear wall is similar to that of cast-in-situ shear walls with openings. Compared with the cast-in-situ shear wall with opening, the load-carrying capacity and stiffness of the precast shear wall similarly decreased with the increasing opening area ratio; and the stiffness of the precast wall decreased up to 47.6%. The wall beneath the window opening can slightly compensate for the weakening effect of the unspliced vertical bars on cracking, but the vertical location of the opening had little effect on the lateral behaviour of the precast shear wall with unspliced vertical distribution bars. Finally, the length of the cast-in-situ boundary elements of the precast shear wall was more influential in the stiffness rather than the load-carrying capacity of the shear walls.

Qi Cai, Xiaobin Song, Xuwen Xiao

Structural Health Monitoring and Sensor Technologies for Civil Infrastructure

Evaluation of the Application of Unmanned Aerial Vehicle Technology on Damage Inspection of Reinforced Concrete Buildings

As for the damaged structures that suffered a destructive earthquake, damage inspection is essential to evaluate the seismic safety as well as assess the long-term performance for planning a suitable structural rehabilitation strategy for further service. However, the conventional inspection method by human hands is time-consuming, highly costly, and highly risky for inspectors’ life safety in the fieldwork. To summarise the current situation for structural damage inspection and explore the future potentials of newly-developed technology in this field, the application and usage of unmanned aerial vehicles (UAVs) that are commonly known as drones have been reviewed and evaluated herein. Presented in this study is the basic concept of the UAV-based damage inspection, in which drones are employed as useful tools to inspect and monitor the damaged condition of buildings by collecting photography data. Besides, a conceptual comparison with the conventional approach is consequently given for understanding the advantages and limitations of the UAV-based damage inspection approach. Also, discussions composing of instructions, recommendations, existing challenges, and future directions to address the UAV-based damage inspection approach into further practice are suggested.

Jiehui Wang, Tamon Ueda
Capture of Crack Evolution for Evaluation of Concrete Properties Using Dynamic Mode Decomposition

Cracks on concrete surface provide the earliest indication in structural damage diagnosis and durability evaluation. Currently, most image-based crack detection methods focus on static image, which is not optimal for tracking the evolution of cracks. To address this shortcoming, a novel crack detection method based on dynamic mode decomposition (DMD) of video images is developed. The DMD spectrum, based on two-dimensional matrix formed by a sequence of video frames, is employed to identify cracks from each video frame according to the distribution of eigenvalues. The method is demonstrated using the flexural test of ultrahigh-performance concrete (UHPC) in the laboratory. The surface cracks identified agree well with those of the original image. The total crack area and its projections on two major directions were computed. The relationship between crack development and force-displacement state was investigated. The crack propagation of UHPC and its effect on mechanical characteristics were revealed from analysis of the captured images. In this crack detection procedure, the cracks of concrete surface do not require any special marks and the video can be recorded using a smartphone. The simplicity of the proposed method and its ability to produce good results make it attractive for practical applications.

Jixing Cao, Ser-Tong Quek, Yao Zhang
Model Updating with Neural Network Based on Component Model Synthesis

Structural health monitoring usually depends on an accurate finite element (FE) model. Due to the complexity of the structures of long-span bridges, the initial FE model usually needs updating to reduce model errors and improve prediction accuracy. Neural network, relying on its strong ability of pattern matching, has gradually received more attention in the research fields of structural model updating. However, for large-scale complex structures, the amount of degrees of freedom of the model and the parameters need to be updated is huge. When using a single neural network for model updating, the required set of training data will be extensive to ensure the density of training samples, which leads to low efficiency or even infeasibility of network training. In this paper, a method of model updating with neural network method based on Component Model Synthesis (CMS) is proposed. In the proposed method, the sizeable full structure model is first divided into several substructures, and then each substructure is updated by a small neural network, respectively. After that, the updated substructures are assembled by the Craig-Bampton method, where the information of updating parameters from all substructures to the original complete structure, resulting in an updated full structural model. The feasibility and effectiveness of the proposed method are verified by a numerical simulation example of a FE model updating of a plane truss.

Zihan Cao, Tao Yin
Crack Assessment of Beam Using Machine Learning with Augmented Sensing

The modal frequency of a cracked beam is known to be smaller than that of an intact beam because cracks in the beam do not change the mass and only reduce the rigidity. Most previous studies have focused on assessing the crack location and depth by using the fractional reduction of the modal frequency based on the Euler–Bernoulli (E–B) beam theory. Because the effects of rotational inertia and shear deformation are disregarded in the E–B beam theory, the high-frequency dynamic behavior cannot be predicted appropriately. Furthermore, more than three cracks cannot be identified because 2n modal frequencies are required to assess n cracks, whereas the maximum number of available modal frequencies is six at most, based on previous studies. In this study, the broadband modal frequencies of a cracked beam are accurately predicted by using the Timoshenko beam theory. The use of broadband modal frequencies alleviates the sparsity of measurement information for crack assessment. Using the closed-form solution of the modal frequency for a Timoshenko beam with multiple incipient cracks, the computational cost can be reduced significantly during data augmentation. Data augmentation allows for augmented sensing, thereby providing machine learning with a sufficiently huge database of broadband modal frequencies associated with multiple cracks of arbitrary depths and locations on the beam. The proposed method is validated through the numerical simulation in which the number of cracks is estimated in free-free cracked aluminum beams with up to four cracks.

J. H. Hwang, H. W. Park
Structural Health Monitoring of Steel-Concrete Composite Beams Using Acoustic Emission

Steel-concretes composite structures have been widely used in buildings and bridges during the past decades. However, in the hogging moment regions of steel-concrete composite beams, the concrete slabs are vulnerable to cracks and the connection interfaces are subject to debonding and slip. These damages could substantially reduce the stiffness, strength and durability of the beams. Structural health monitoring of steel-concrete composite beams is thus of interest. In this study, acoustic emission (AE) is applied to detect and characterize damages in steel-concrete composite beams. The damage induced AE sources were located based on Akaike information criterion (AIC)and genetic algorithm (GA), where AIC helped to determine the arrival time of AE waves more accurately in the presence of noise and GA helped to find the optimal location considering AE waves received by all the sensors. With located AE sources, the damage size could also be estimated. After that, the crack types and orientations were diagnosed based on MTA. Through inversed four-point bending test, the proposed method was proved to be able to identify concrete cracks and steel-concrete debonding damages in steel-concrete composite beams with different sizes of headed studs. The beam with studs of lower shear capacity behaved with higher concrete crack resistance, and the dominant damage mechanism in the concrete slab was found to be tensile-mode cracks.

Dan Li, Jia-Hao Nie, Jia-Bao Yan, Chen-Xun Hu, Peng Shen
Predicting the Modal Frequencies of a Cracked Beam Considering Crack Modes I and II

Surface-mounted piezoelectric wafers allow for the evaluation of the dynamic characteristics of a cracked beam in the high-frequency range. The modal coupling between the adjacent axial and bending modes of the cracked beam was observed in the high-frequency range. The modal frequencies do not change in the low-frequency range owing to a crack located on the bending node of an intact beam. However, mode II crack causes a reduction in modal frequencies, particularly in the high-frequency range, in the presence of the crack on the bending node. When a crack is arbitrarily located on a beam, modal frequencies in the high-frequency range are simultaneously affected by mode I crack, which is associated with the axial-bending mode coupling, and mode II crack. The effect of mode I crack on the reduction in the modal frequency is dominant, except for the crack on the bending node. Mode II crack became more sensitive to the reduction in the modal frequency as the mode number increased. Therefore, crack modes I and II should be taken into account simultaneously for the accurate prediction of the modal frequency, which enables reliable crack diagnosis of a beam. In this study, the modal frequencies of cracked beams were predicted by considering both crack modes I and II. The characteristic equations of the cracked beam were derived from the compatibility equation corresponding to crack modes I and II, equilibrium equations, and boundary conditions. The modal frequencies calculated from the characteristic equations were verified through a comparison with the finite element analysis and experimental results.

Taejeong Lim, Hyun Woo Park
Deep Learning-Based Crack Detection and Classification for Concrete Structures Inspection

Automatic crack detection is a main task in a crack map generation of the existing concrete infrastructure inspection. This paper presents an automatic crack detection and classification method based on genetic algorithm (GA) to optimize the parameters of image processing techniques (IPTs). The crack detection results of concrete infrastructure surface images under various complex photometric conditions still remain noise pixels. Next, a deep convolution neural network (DCNN) method is applied to classify crack candidates and non-crack candidates automatically. Moreover, the proposed method compared with the different deep learning methods for crack detection. The experimental results validate the reasonable accuracy in practical application.

C. K. Nguyen, K. Kawamura, H. Nakamura

Bayesian System Identification of Civil Engineering Structures: Development and Application

Finite Element Model Updating Based on Neural Network Ensemble

Over the last few decades, structural health monitoring (SHM) has been gaining more and more attention, especially in civil engineering. Due to the assumptions and uncertainties in finite element (FE) modelling, there are inevitably various errors between the dynamic characteristics predicted by the FE model and the measured data. So it is necessary to calibrate the initial structural model, which is a typical inverse problem, and generally ill-posed. As a powerful artificial intelligence technology, artificial neural network (ANN) has been widely used in model updating due to its excellent pattern recognition ability. Compared with the traditional ANN approach, the Bayesian Neural Network (BNN) method is more robust to noise. However, with the increase in the number of dimensions and hidden neurons, the amount of samples required for training neural networks and the corresponding time consumption shows catastrophic growth, especially for training a single neural network to update large-scale FE models of civil engineering structures. To make progress, the ensemble of multiple neural networks fed with divided training sample sets is a feasible strategy. It is expected to improve the generalization performance compared to a single network for handling large-scale FE models, which is seldom emphasized in the current literature related to the FE model updating. This paper proposes a FE model updating method that utilizes the strategy of neural network ensemble by utilizing the modal flexibility matrix as the training input. The entire set of training samples is further divided into a series of smaller sample sets and used to train multiple BNNs, the final identification result is obtained by summing the outputs weighted by the evidence of each individual model. A truss model is employed in this paper to validate the feasibility and effectiveness of the method.

Yuxuan He, Tao Yin
Damage Statistics and Integrity Assessment of Brick Masonry Structures in Historic Buildings

Deterioration faced by brick masonry structure of historical buildings is more and more concerned. In this paper, two methods, statistical classification and quantitative mapping, have been carried out to analyze the damage apperance of the southeast and northwest facades based on a historical building project in downtown Shanghai. Then damage distribution characteristic and integrity assessment have been further analyzed. Statistics show that the damage area ratios on southeast and northwest facade are 8.71% and 8.06%, respectively. Specifically, dampness, saltpetering and peeling are three main damage features to these two facades. The damage distribution curves of the both in vertical direction have the similar appearance, Both show that the sum of damage reaches the maximum value at the level of 2 m above ground surface, and then gradually decreases with the elevation increase. In addition, the total damage length also increases near height of 9 m.

Haiyang Qin, Yongjing Tang, Jiao He, Zhiwang Gu
Multi-view Target-Free Video Structural Motion Estimation: A Self-adaptive Co-calibration Model

Target-free magnification-based vibration measurements can be used to compute the full-filed dynamic response of structures, which alleviate the need for structural surface preparation and can be implemented in an efficient and autonomous manner. However, up until now, such methods have limitations in the measurement range of motion that can be estimated, which fundamentally restricts their applicability. Moreover, they are only for one-dimensional (1D) or two-dimensional (2D) measurement. A rapid and accurate multi-view video estimation method is highly demanded. This paper presents a novel multi-view target-free video structural motion estimation method based on a self-adaptive co-calibration model. The model is derived from the maximum likelihood formulation with sparsity priors. Fast cosine transform with extension to phase correction operation across the levels of multi-scale pyramid is introduced. To apply it to three-dimensional (3D) video estimations, an iteratively reweighted method is employed to handle the lq-norm multi-view minimization problem. The proposed method is demonstrated in case studies considering analyses of video motion estimates for structural health monitoring (SHM). Compared to conventional methods, the proposed method provides more accurate measurement of structural motions in both time and frequency domains.

Yi Zhang, Enjian Cai
A Robust Bayesian Sensor Placement Scheme with Enhanced Sparsity and Useful Information for Structural Health Monitoring

For the application of structural health monitoring in civil engineering structures, one common bane is the need for sensors. Optimizing the type of sensors, the number of sensors, and the location of sensors is therefore important in ensuring that the most optimal amount of information is obtained from measurement data while making the monitoring systems (including the sensors) economical. In this study, the issue of sensor placement is addressed by developing a simple Bayesian scheme based on information entropy and progressive increment or decrement in the number of available sensors. Compared to other conventional placement schemes available in the literature, the proposed scheme offers a simple yet robust configuration optimization, with results almost always the same as a full one-by-one search through all possible configuration candidates. The proposed scheme also provides enhanced sparsity of sensors by incorporating a spatially correlated covariance matrix for the measured data. The enhanced sparsity ensures that more “useful” information is contained in the measured data. To verify the proposed scheme’s acclaimed improvement, especially for damage detection purposes, the analysis results for configurations selected by conventional algorithms and those selected by the proposed scheme are compared for a ballasted track system. Results clearly show significant improvement in configurations’ optimality, with minimal computational cost.

Mujib Olamide Adeagbo, Heung-Fai Lam
Investigation of the Performance of a Bioinspired Two-Fold Blades Wind Turbine with Airfoil Blade Sections by Using QBlade

The current study focuses on the investigation of the power and thrust performance of a new two-fold blades wind turbine design by using blade element momentum (BEM) based wind turbine analytical software, namely the QBlade. The two-fold blades wind turbine is a downwind, 3-bladed airfoiled wind turbine that consists of a root fold axis and a mid-span fold axis. The blade sections are shaped by using the SD8000 airfoil. The idea of folding the straight blade wind turbine was inspired by the winged seed of the Borneo Camphor tree (Dryobalanops aromatica), which consists of wings that are folded. It was presumed that the folding of the wind turbine blades would alter the pitch and cone angles of the blade sections, which consequently affect the angle of attack, changing its power and thrust performance. Fixed fold axis angles and two levels of fold angles were applied to the root and mid-span fold axis. The unfolded wind turbine blade was also the benchmark wind turbine adopted from the study conducted by a previous researcher. This unfolded wind turbine blade was with the size of one meter in diameter and with a constant chord length of 90 mm throughout the span. The fold at the root made the blade tilt towards the downstream direction, while the mid-span fold tilts the blade tip towards the upstream direction in an attempt to mimic the folding pattern of the wings of Borneo Camphor seed. The analytical results show that under the wind speed of 10 m/s, the proposed two-fold blades wind turbine outperformed the benchmark (unfolded) wind turbine at low tip speed ratios. Thus, this confirms the potential application of the two-fold blade wind turbine design in the wind energy industry, where it can be used in power regulation through folding mechanisms.

Yung-Jeh Chu, Heung-Fai Lam, Hua-Yi Peng
A Bayesian Adaptive Resize-Residual Deep Learning Network for Fault Diagnosis of Rotating Machinery

Due to the high accuracy achieved in data-driven fault diagnosis, time-frequency images generated by Continuous Wavelet Transform (CWT) are widely used as the input of deep learning methods. However, the image data require huge amount of data memories. An adaptive resize technique provides a reliable way for deducing the scale of image and achieving good effect. In this study, a novel Bayesian adaptive resize-residual network was proposed to resize the input data scale and extract the image feature for mechanical fault diagnosis. The CWT and Histogram Equalization (HE) algorithm were used to generate enhanced time-frequency images. The newly developed adaptive resize-residual network was applied for feature extraction, in which the adaptive resize block can adaptively resize input image by self-learning, and the residual block was used for classification. The Bayesian optimization was introduced to optimize the model hyper parameters and obtain an effective model. A testbeds of rolling element bearings are introduced to support the experiments. The experimental results indicate that the proposed Bayesian adaptive resize-residual network obtains superior recognition accuracy and outperforms many state-of-the-art methods. This method is conducive to improving the capabilities of rotating machinery fault diagnosis, and reduces the repair time of fault.

L. Zou, K. J. Zhuang, J. Hu

Mechanics of Materials and Structures with Generalized Continua: Flexible Structures, Composite Materials, Optimizations, and Applications

Nonlinear Vibrations of Deepwater Catenary Riser Subjected to Wave Excitation

The purpose of this research is to present the mathematical model for the nonlinear vibration analysis of a deepwater catenary riser subjected to a wave excitation. The mathematical model of the catenary riser is derived from the work-energy principle, including the geometrical nonlinearity and nonlinear loading from a square drag term of hydrodynamic force. The finite element method is used to form the equation of motion for solving the numerical solution. The nonlinear equation of motion can be written in the appropriate form, which is convenient to perform the numerical integration. The Newmark time integration incorporated direct iteration is used to solve the nonlinear vibration response of the catenary riser. The nonlinear forced vibration analysis is carried out for both small and large vibration amplitudes. From numerical investigation, it was found that the vibration response of the riser due to wave force is a harmonic motion and the vibration amplitude increases as the increasing in wave amplitude. In addition, the effect of nonlinear geometry has a significant influence on the vibration amplitude of the riser.

Nutwadee Lertchanchaikun, Karun Klaycham, Chainarong Athisakul, Somchai Chucheepsakul
Effects of High Turbulence Intensity on Dynamic Characteristics of Membrane Structure in Typhoon

To investigate the effects of high turbulence in typhoon on the aerodynamic characteristics of membrane structure, wind tunnel tests of an umbrella-shaped tensioned membrane structure were carried out in both typhoon and traditional atmospheric boundary layer in terrain B field (B-type). Dynamic identification of the aeroelastic model in these two wind fields are discussed in terms of frequency, modal shape and damping ratio. Results show that the influences of high-level turbulence intensity are (i) the fluid-structure interaction in typhoon becomes more severe with larger damping ratio, resulting in the reduction of displacement response and frequency, (ii) the frequencies in different order distribute closely in some narrow bands and perform localization, and (iii) the non-Gaussian distribution of displacement response appears more obvious in typhoon condition, which should be considered in reliability design of membrane structure. This study can address the deficiency of current studies for dynamic characteristics of membrane structure in typhoon.

Dong Li, Yiteng Lin, Hongwei Huang
Effects of Discretization Schemes on Free Vibration Analysis of Planar Beam Structures Using Isogeometric Timoshenko-Ehrenfest Beam Formulations

Several Timoshenko-Ehrenfest beam formulations have been presented in the literature for analysis of planar beam structures. In general, the displacements of the beam axis and the cross-sectional rotation are taken as kinematic unknowns. Two discretization schemes are available, namely discretization of local displacements and discretization of global displacements. In the case of linear static analysis, it has been shown that discretization of local displacements fails to accurately represent rigid transformations, whereas discretization of global displacements does not. Consequently, numerical instability is observed in analysis using discretization of local displacements. This paper investigates the effects of the two discretization schemes on free vibration analysis of planar beam structures using isogeometric Timoshenko-Ehrenfest beam formulations. Several numerical experiments on a free-form cubic beam are used for the investigation. In terms of accuracy, better performance from a formulation that employs discretization of global displacements is noticed.

Duc Van Nguyen, Duy Vo, Pruettha Nanakorn
Geometrically Nonlinear Behavior of L-Shaped Frames Under Forces Applied at Different Positions

L-shaped frames are widely encountered in engineering applications, and the most notable examples are perhaps cranes at container ports and construction sites. In these applications, L-shaped frames are designed to support vertical and horizontal movements of heavy loads. For their safe and efficient designs, thorough insights into the nonlinear behavior of such frames are crucial. Although several studies on geometrically nonlinear responses of L-shaped frames exist, a single force applied at a specific position is commonly considered. For a comprehensive reflection of practical operations of L-shaped frames, this paper presents a numerical investigation of the geometrically nonlinear behavior of L-shaped frames under a concentrated force applied at different positions. The frames are analyzed by using an isogeometric Timoshenko-Ehrenfest beam formulation. The load-displacement curves of the frames with different force positions are exhibited. The influence of the ratio between the lengths of the two members is also discussed.

Nghi Huu Duong, Duy Vo, Pruettha Nanakorn
Interfacial Displacement Discontinuity in Coated Substrate with Couple-Stress Effects

A size-dependent elastic response of a thin-layer-coated substrate induced by a finite-length interfacial displacement discontinuity is fully investigated in the present work. The material microstructures responsible for the size effects are simulated within a continuum-based framework via the couple stress elasticity theory. A method of Fourier transform is adopted first to derive the general solution of an elastic field for both coating layer and coated substrate. The boundary conditions on the free surface, the continuity and discontinuity conditions along the coating interface, and the remote conditions are subsequently enforced together with the established general solution to solve for all key unknowns. Results are collected to demonstrate the effect of material contrast between coating layer and coated substrate and the crucial role of material microstructures on predicted response as the length of displacement discontinuity and the thickness of coating layer becomes comparable to the material length scale.

W. Wongviboonsin, P. A. Gourgiotis, J. Rungamornrat
Mechanical Properties of Lattice Specimens Having a Triangular Pattern with Different Relative Densities

This study experimentally investigates the mechanical properties of lattice specimens with triangular unit cells using a tensile test, including Young’s modulus and yield strength. The lattice specimens made of 316L stainless steel are fabricated by a metal 3D printer. The mechanical properties of the lattice specimens with different relative densities are studied. Formulas of the normalized Young’s modulus and normalized yield strength of the lattice structure obtained from the literature are used to validate the experimental results. The discrepancies between the normalized results obtained from the experiment and the formulas are also discussed.

Itthidet Thawon, Pana Suttakul, Thongchai Fongsamootr, Yuttana Mona
Analytical Solution for Circular Microbeams with Strain Gradient Elasticity

In the analysis of skeletal structures, circular beams are widely studied since their simple geometry allows the derivation of analytical solutions which are useful tools to assess the accuracy and efficiency of numerical ones. With such feature, the present study aims mainly to establish the key governing equations, boundary conditions, and corresponding analytical solutions of circular microbeams within the framework of strain gradient elasticity and Timoshenko-Ehrenfest beam theories. It is worth highlighting that the curviness is also included in the formulation, and its influence on the predicted responses is explored. A solution procedure is implemented to establish the analytical solutions for general loading and boundary conditions. A representative semi-circular beam is subsequently analyzed with the adopted procedure, and a selected set of results is reported to illustrate the effects of the curviness.

Zwe Yan Aung, Duy Vo, Toan Minh Le, Jaroon Rungamornrat
Free Vibration Analysis of Toroidal Shell Segments with Novel Four-Unknown Refined Theory

This study presents an analytical solution for the free vibration response of toroidal shell segments subjected to different boundary conditions. The shell segments are made of a functionally graded graphene platelet reinforced composite (FG-GPLRC). The modified Halpin-Tsai model together with the rule of the mixture is adopted to derive the effective material properties of the nano-composites. The governing equation of motion for the shell is formulated within the framework of the novel four-unknown refined shell theory. The positive feature of such adopted shell theory results directly from the reduction of the number of key unknowns, without using the shear correction factor. The Rayleigh–Ritz procedure is subsequently implemented to determine the natural frequencies of the shell with different boundary conditions. Finally, numerical results and useful remarks on the free vibration of the shells are provided.

Van-Loi Nguyen, Suchart Limkatanyu, Jaroon Rungamornrat
Linear Analysis of Planar Curved Bi-directional Functionally Graded Microbeams Using the Modified Couple Stress Theory

This paper presents an efficient formulation for linear analysis of planar curved microbeams made of bi-directional functionally graded materials. The formulation is derived using the modified couple stress theory in conjunction with the kinematic assumptions of the Euler-Bernoulli beam theory. Univariate non-uniform rational B-spline (NURBS) basis functions are used to discretize the kinematic unknowns. In addition, the volume fraction of materials is described by a NURBS surface to enable the consideration of arbitrary variations of material properties in two directions, i.e., the directions of the beam axis and cross-sectional height. To validate the presented formulation, linear static and vibration analyses of a semi-circular microbeam are performed. Since the exact solutions of the considered problems do not exist, the reference solutions are obtained with significantly many isogeometric plane elements, and the accuracy and efficiency of the proposed formulation are assessed.

Duy Vo, Pana Suttakul, Jaroon Rungamornrat, Pruettha Nanakorn
Steel Braces Optimization Design of Steel Tall Building Based on Stiffness Performance Sensitivity Data

Complex high-rise steel structures have many design variables. Through sensitivity analysis of grouping of different types of components, it can be determined that optimizing the form, quantity and arrangement of steel braces can effectively reduce the maximum inter-story drift, which is the controlling wind response of the structure, so as to save the time cost of optimization. Adjusting the form, quantity and arrangement of steel braces to achieve the ideal steel consumption on the premise of satisfying the limit of maximum inter-story drift is a process of re-analyzing the modified results and guiding the next modification until the results converge. An effective re-analysis method can also reduce the calculation times and save the time cost of optimization. In the optimization process, sensitivity analysis and reanalysis are indispensable. In this paper, high-rise braced steel frame structure is taken as the research object and the steel braces are divided into groups according to different vertical zones and different plane positions, to analyze the sensitivity of maximum inter-story drift under wind load to different groups of steel braces, and to study the reanalysis method of specific steel structure system, specific design constraints, and specific optimization variables, so as to achieve rapid and efficient optimization design. Finally, a 150 m high-rise steel structure residence is taken as an engineering case to verify the correctness of sensitivity analysis results of high-rise steel structure for wind vibration stiffness performance control, and the effectiveness and practicability of re-analysis method in optimization design.

Yuzhou Hou, Xin Zhao
Sensitivity Data Driven Composite Floor Structural Optimization for Tall Office Buildings

In tall office buildings, steel beam composite floor system is a popular solution for floor systems as it is known for requiring less construction time and having good weight-to-strength ratio. However, despite being a relatively light-weight floor system, steel beams in composite floor systems are still accountable for a large percentage of buildings’ self-weight. Therefore, optimization of this floor system design is still required, especially for tall buildings, and it can be achieved by reducing the weight of steel beam supporting the composite deck. In this paper, optimization methods, Multiple Decomposition Method and Sensitivity Data Driven Algorithm, are employed to design and optimize a large span steel beams supporting deck floor of a tall office building. Based on Multiple Decomposition Method, the composite floor’s beams are divided into three substructure levels. To global structural performance, the 1st level which consists of the entire composite deck floor aims to achieve floor the serviceability performance. Subsequently, the 2nd level involves serviceability requirement of composite beams within the floor. Lastly, the 3rd level consists of structural elements such as the composite deck, steel beams, and shear studs, and the optimization problem is related to sizing the cross-section dimensions of each beam to meet the design requirements from both the 2nd level and 3rd level. In addition, Sensitivity Data Driven Algorithm is also used to further determine design constraint sensitivity coefficients to design variables as guidance to examine optimum beam sizing proportion.

Morn Chornay, Xin Zhao
Load-Resistant Mechanism and Failure Behaviour of RC Flat Plate Slab-Column Joints Under Concentric and Eccentric Loading

Progressive collapse, usually caused by accidental or abnormal loading, is a structural failure disproportionate to its original cause. Reinforced concrete (RC) flat plate structures are vulnerable to brittle punching shear failure in the vicinity of slab-column joints, which may initiate disastrous progressive collapse causing significant economic, social, and psychological consequences. This paper presents a series of experimental investigations of twenty-one 1/3-scaled slab-column joint specimens with in-plane restraints, under opposite punching shear directions, and subject to concentric and eccentric loading conditions. Three design parameters (slab thickness, reinforcement ratio, and flexural reinforcement extension) and three strengthening methods (embedded beams, stirrups in punching area, and ring beams) were considered. The load-resisting and deformation capacities of the joints, as well as their punching shear and post-punching failure behaviours were examined in detail. In addition to the experimental studies, numerical modelling techniques were also developed to simulate the physical tests with emphasis on their load-displacement responses, punching shear and post-punching capacities and crack development. Results demonstrate that (1) the punching shear capacity is mainly governed by the geometrical dimensions of the slab; (2) the post-punching strength is primarily regulated by the integrity rebars going through the column. The continuous integrity rebars are imperative for activating tensile membrane action thereby enhancing post-punching capacity in progressive collapse events.

Mengzhu Diao, Hong Guan, Huizhong Xue, Yi Li, Xinzheng Lu
Numerical Simulation for Parallel-To-Grain Withdrawal Failure of Self-tapping Screws in Glulam

The exploration of connection technology is an important topic in the field of modern timber structure. Tapping in manufacturing is the process of cutting threads inside a hole, and self-tapping screw, as the name implies, is a mechanical fastener that can enter the matrix material (wood) and cut threads on the internal surface of a pre-drilled hole by itself. Compared with the glued-in steel rod used as the axially-loaded fastener in timber connection, the self-tapping screw can be applied as a kind of new axially-loaded fastener without applying adhesive in assembly. The mechanical interlocking through the tight fit of the thread pair between the screw and the wood promises a method of realizing the strong and stiff connection in timber structure. In order to take full advantage of this fastener in axial load transfer, the withdrawal failure mechanism of self-tapping screws in wood needs to be researched to avoid the withdrawal failure at first. A numerical model containing contact analysis and considering the material damage of failure surface is constructed to simulate the parallel-to-grain withdrawal failure of the self-tapping screw in glulam by the finite element method program ABAQUS/Explicit. The steel-wood friction coefficient in contact analysis and the self-defined parameters aimed to reflect the stiffness in the bi-linear traction-separation law are used as trial parameters in simulation. The model results for the parallel-to-grain withdrawal capacity of the screw are found to be in a good agreement with the experimental results. The trial calculations imply that the steel-wood friction coefficient in contact analysis has no obvious influence on the withdrawal capacity/stiffness of the screw; however, the ratios of initiation displacement and failure displacement in the traction-separation law have negligible influence on the withdrawal capacity but significant influence on the withdrawal stiffness of the screw.

Lijing Fang, Wenjun Qu, Shengdong Zhang

Advances in Design and Intelligent Optimization of Large-Span Bridge

A Study on Time Synchronization Method for Creating a Cable Surface Image of Cable-Stayed Bridge Using Image Processing

The authors have developed a cable-stayed bridge (CSB) cable inspection robot to improve the efficiency of cable inspection of CSB. Six cameras were mounted on the robot, which takes a video of the whole circumference of the cable surface as it moves up and down the cable. The method is characterized by making an image development diagram from the taken video. In this paper, the red LEDs on the green base plate are installed in the CSB cable inspection robot in order to synchronize the cameras. Then, a time synchronization method using image processing is proposed to automatically detect the red LEDs from the taken video. Finally, this paper discusses the results of automatically detecting the detection accuracy of red LEDs lighting from the actual videos of the inclined cables, which demonstrate the robot’s ability to improve work efficiency and reduce workplace hazards.

Z. Wei, K. Kawamura, T. Nakamura, M. Shiozaki
Assembly Fault-Tolerant Interval Inversion Method for Cable-Stayed Bridge Based on Bilayer Surrogate Model

Focusing on the assembly accuracy control problem of practical engineering and installation tolerance ability under uncertain interference, this paper presents an interval inversion method derived from reliability-based optimization design (RBDO) scheme. The proposed method is applied to the tolerance planning of cable tensioning process of an example cable-stayed bridge. In this paper, the midpoint and radius of the controllable parameters are taken as the optimization variables, and a decoupling evaluation framework based on bilayer surrogate model is established to quantify uncertainty, and then the maximum tolerance range is efficiently extracted from the highly coupled design objectives. The results illustrates that the proposed method not only effectively saves calculation resources, but also ensures high accuracy. The application of tolerance interval to guide engineering decision-making process has shown better inclusiveness to the error accumulation during construction, which improves the construction resilience under the influence of manufacturing and assembly errors.

Fan Wang, Jianling Zhao, Xiaoming Wang, Pengfei Li, Pei Tao
Dimensionless Continuum Model of Vertical Free Vibration of Spatial Self-anchored Suspension Bridge

Due to the spatial coupling of main cable-hanger and the internal self-balance between subsystems, the free vibration continuum model of spatial self-anchored suspension bridge is difficult to establish, which limits the acquisition and identification of its dynamic characteristics. In this paper, the vertical free vibration continuum model considering hanger tension is established by integrating the vibration form deflection theory and the deformation and compatibility equation of main cable-hanger-beam, which is dimensionless to identify the characteristic parameters controlling dynamic characteristics; The shape function of main cable and girder satisfying the geometric and mechanical boundary is constructed, and the model is transformed into matrix form by Galerkin method to solve the modal frequency and vibration mode; Numerical examples and finite element models are used to verify the universality and accuracy of the continuum model, and the sensitivity of key stiffness characteristic parameters is analyzed. The results show that the relative elastic bending stiffness of the main girder significantly affects the modal frequency, and the elastic stiffness of the main cable only slightly affects the symmetrical modal frequency; The elastic axial stiffness of the hanger is sensitive to the relative elastic bending stiffness of the main girder. Whether the hanger tension is considered or not will significantly affect the high-order modal frequency, especially the antisymmetric mode. In conclusion, the continuum model considering hanger tension is more accurate, which can provide an effective reference for the preliminary design of the project and the real-time planning of dynamic disaster prevention and control scheme.

Jianling Zhao, Fan Wang, Xiaoming Wang, Pei Tao, Pengfei Li
Dynamic Modal Parameters of an Extremely Lightweight Structure Using a Gyroid Core for Bridge Bearings

This article reports an extremely lightweight structure used as a sandwich core for bridge bearings due to their superior mechanical properties, such as sound and vibration attenuation, rigidity, and energy absorption. The structure is based on triply periodic minimal surfaces (TPMS) conceived by observing the scales of butterflies’ wings. The vibration behaviours of this innovative structure used in these bearings are not well-known and have never been fully investigated. Therefore, it is important to comprehend their vibration behaviours and also to identify dynamic modal parameters of these bridge bearings. Two gyroid sandwich panel finite element models with different unit cell sizes used as bridge bearings are examined with a computational method. The numerical investigation shows the vibration mechanisms and provides the dynamic modal parameters important in establishing relationships between its mechanical performance and geometry. Finite element predictions of the vibration behaviours of the two models with different unit cell sizes under free vibration provide good results. These results can be implemented to better generate informed lightweight structure designs for bridge bearings, which are subjected to different vibration conditions.

P. Sengsri, S. Kaewunruen
Exploring Patterns in Municipal Bridge Management Issues and Their Relationship with Municipal Conditions in Hokkaido, Japan

Following legislation passed in 2013, the Japanese government now requires the visual inspection of road bridges every five years. Over 700,000 bridges have been inspected as of 2021, of which nearly two-thirds are under the management of municipal governments. Results have shown that the number of municipal bridges in need of early or urgent repair is much greater than that at other management levels; however, many municipalities lack the necessary financial and human resources to realize maintenance of their bridge infrastructure. As a result, bridge management at the municipal level is becoming a critical issue for ensuring the safety of road infrastructure in Japan, but there are notable disparities in the challenges facing bridge management even within the municipal level. In this research, cluster analysis is adopted to explore patterns in the bridge management issues faced by local municipalities in Hokkaido, the prefecture with the most municipalities in Japan. Publicly available bridge inspection data and socio-economic data were collected at the municipal level, and a set of descriptive features was constructed. Cluster analysis was then carried out twice – once to identify patterns in municipal bridge management issues, and once to identify patterns in municipal conditions – and the relationship between these results was examined. It was found that, while there are a few highly unique municipalities, most municipalities possess fairly similar bridge management issues and municipal characteristics, which could be judged as the “average” conditions in Hokkaido. Furthermore, there was generally an overlap between the “average” bridge management conditions and “average” municipal conditions, although some municipalities with “average” conditions did exhibit unique bridge management issues.

Michael Henry
Mechanical Model for Parallel-to-Grain Withdrawal Failure of Self-tapping Screws in Glulam

In response to the goal of carbon neutrality under the background of global climate crisis, timber as a kind of bio-based material regains a new attention in the field of building. When the building industry hopes to promote timber structure in practice, existing connection techniques are in urgent need of innovation. Currently the improving screw manufacturing process can supply the threaded fasteners such as self-tapping screw or threaded rod with sufficient lengths and optimized threads to the market, which provides a promising technical solution to realize the strong and stiff timber connections. Distinguished from the common laterally-loaded metal fasteners such as dowel and bolt, the self-tapping screw can be regarded as a kind of fastener capable of load transfer along the direction of its axis. Before the application of this axially-loaded threaded fastener in timber connection, the withdrawal failure mechanism of self-tapping screw in wood should be researched in depth to avoid the withdrawal failure at first. Different from existing models based on the classical theory of Volkersen, a new mechanical model for parallel-to-grain withdrawal failure of self-tapping screws in glulam is proposed in this paper. “Assembly unit”, which can be assembled to the whole fastener surrounded with failure wood and disassembled to some discrete parts, is first introduced as a mechanics analysis unit in this model to research the withdrawal failure of self-tapping screws in glulam and calculate the anchorage length of self-tapping screws in glulam. The model considers the distinctive mechanical behaviors caused by the thread of the screw: the local stress of wood filled in the screw pitch and the discontinuous transfer of shear stress/force on the failure surface. The theoretical calculations achieve an acceptable agreement with the results of two experimental investigations, and the reasons affecting the accuracy of the model are discussed for further improvement.

Lijing Fang, Wenjun Qu, Shengdong Zhang

Practice of Sustainable Urban Development

A Study on Estimation Method of Curing Influence Area for Prediction of Remaining Life on Real Concrete Structures

The life cycle of concrete structures is known to be highly dependent on the manufacturing, construction and the environment of the structure’s location. In order to keep the durability of concrete, it is necessary (1) determination of materials and mix proportion on design, (2) keeping the enough compaction and curing period on construction and (3) understanding the environmental effects such as supply of carbon dioxide, chloride ions and water. Therefore, it is important to implement the design with the required performance to satisfy the design service life. On the other hand, in maintenance management, it is necessary to predict the remaining life based on the supplying period and the state of deterioration at that time. In this case, the information at the time of design and construction is often unknown, and it is difficult to estimation. In this study, as a first step to sort out these issues, concrete specimens were prepared using various types of cement, varying the water cement ratio and also varying the curing period. The accelerated carbonation test and vacuum water absorption test were combined to represent the penetration of carbon dioxide and water in the specimens. The area of influence of curing was organized in terms of material and mix proportion conditions. Porosity was also measured to evaluate the relationship between the penetration properties. In addition, wall specimens were also prepared to measure the effect of curing by non-destructive test. As a result, it was confirmed that the larger the water cement ratio, the greater the effect of curing on the surface layer, but the depth of curing effect was about 20 mm. It was also confirmed that the effect of curing and curing area were larger for Low heat Portland cement and high replacement blast furnace slag cement, where the hydration would slower.

T. Iyoda, A. Sugiyama, M. Miyawaki
Design Method on Flexural Behaviour of Singly-Reinforced PVA-ECC Beams

Polyvinyl alcohol-engineered cementitious composite (PVA-ECC) is superior to normal concrete in terms of tensile strain capacity and crack mitigation. On account of the significant strain-hardening behaviour, the tensile strength of PVA-ECC should be considered in the design of reinforced PVA-ECC members. In this paper, a design method is proposed to evaluate the flexural resistance of reinforced PVA-ECC members based on the classified failure mode. Simplified constitutive models in compression and tension are adopted in the design method. Limiting reinforcement ratios, namely, minimum reinforcement ratio, balanced reinforcement ratio and yielding reinforcement ratio, are also determined for different failure modes of beams. Finally, the design method is validated by test results of singly reinforced PVA-ECC beams from different literature to assess its accuracy. Comparisons between experimental and analytical results show that the design method is reasonably accurate in estimating the load-bearing capacity of reinforced PVA-ECC beams.

Dan-Dan Wang, Shao-Bo Kang, Xiao-Fan Yu, Kun Liu, Xun-Tian Tan
Earthquakes, Reinforced Concrete Structures, and Circular Economy: A Systematic Review of Studies

Due to large earthquakes, reinforced concrete structures were damaged or eventually demolished. Various building codes (ACI 318-11, 2011; EN-8, 2004) for the design of buildings incorporated a seismic design approach to allow for ductility of building structures during an earthquake. This design approach has been effective in terms of protecting people’s lives. Nevertheless, it may not be sufficient for post-earthquake services in seismic-prone regions. Intending to provide a low embodied carbon structural solution, a new approach called circular economy (CE) has the potential to significantly improve the construction sector’s sustainability, studies on seismic-resistant structures using recycled construction materials revealed that the seismic performance of recycled concrete structures is acceptable. A comprehensive review of peer-reviewed journal articles published from 2012 to 2021 on the earthquake-resistant reinforced concrete structure and circular economy has been considered. Several articles show that reinforced concrete buildings in seismic-prone areas designed based on the current seismic design provisions have shown unacceptable performance. In parts of the region with proactive retrofit policies, like those of Japan, Italy, and New Zealand, the percentage of collapses and severely damaged buildings is lower than anticipated. This suggests that improved seismic design including retrofitting can significantly improve building performance during an earthquake. In this paper, various studies have been reviewed and summarized on the earthquake resistance of reinforced concrete structures, retrofitting techniques, earthquake estimation of seismic action on structures, and circular economy.

Teklewoin Haile Fitwi
Influence Mechanism of Farmers’ Sense of Gain in Tourism-Oriented Rural Infrastructure Construction and Operation

During the rapid development of rural infrastructure in China, there are many important issues that have been overlooked, such as the real wishes of farmers and the management of the infrastructure, resulting in the farmers’ weak sense of gain. However, there is still a lack of research on the influence mechanism of the farmer’s sense of gain in the infrastructure development. To propose effective improvement strategies, this research aimed to explore the influence mechanism of the farmer’s sense of gain in the construction and operation of the rural infrastructure. To achieve the above aim, this study (1) proposed hypotheses for the influence mechanism from four perspectives which include the governance of the infrastructure, content of gain, way of gain, and sense of gain through theoretical analysis; (2) developed an evaluation index system for the above four constructs through a comprehensive literature review and rural field investigations; (3) conducted a questionnaire survey and received 107 effective responses from 7 tourism-oriented rural areas in Nanjing, Jiangsu Province, China; (4) used Structural Equation Modelling (SEM) and the software of AMOS to verify the proposed hypotheses. The results showed that content of gain and the way of gain directly affect the farmers’ sense of gain, and the governance indirectly affects the farmers’ sense of gain. And the way of gain has the greatest impact on the sense of gain, followed by access to the governance, and the content of gain has the least impact. The findings of this study first enriched the relevant theories of farmers’ sense of gain in the construction and operation of rural infrastructure. Moreover, the findings provided the theoretical supports for the government authorities to put forward effective governance strategies for the rural infrastructure from the perspective of the farmers’ sense of gain. Finally, the findings helped to identify the key points of the sustainable development of the infrastructure.

Hongtao Jia, Lei Zhu, Jing Du
Numerical Analysis of Reinforced Concrete Composite Wall Under Concentric Axial Loading

Singapore is one of leading countries developing advanced prefabrication technology for high-rise buildings. The high-quality precast technology is achieved in Singapore mainly due to the good quality of regulation processes. One of the precast technologies adopted is Prefabricated Prefinished Volumetric Construction (PPVC), as part of Singapore Construction Industry Transformation Map. Concrete PPVC method involves structural members, such as beams, columns, slabs, and walls, to be designed and manufactured off-site and transported on-site for installation. There is a need to ensure the structural behaviour of connectivity between PPVC modules. Concrete PPVC connectivity allows proper load transfer to the entire building. A wall-to-wall connection between concrete PPVC modules is introduced in this paper. A reinforced concrete composite sandwiched wall panel is modelled in ABAQUS. Wall panel is formed by connecting two precast reinforced concrete wall panels with grout infill. The concrete property of wall panel is assumed by using ABAQUS built-in function of Concrete Damaged Plasticity model to study the structural behaviour. The wall panel is subjected to axial load as the wall member is to support gravity loads throughout the concrete PPVC building. This paper aims to study the wall panel structural behaviour under gravity axial load and the failure mechanism in numerical analysis. The wall panel is expected to achieve failure mechanism in buckling due to high axial load and debonding of concrete-to-steel reinforcement region at high stress region.

S. S. Yee, K. H. Kong, R. J. Y. Liew
Patterns in the Social Perspectives of Concrete Industry Stakeholders and Their Impact on the Sustainability Evaluation of Concrete

In order to implement sustainable concrete, it is important to understand the involved people or stakeholders’ opinions about the aspects of the topic. Different perspectives can reflect on their understanding of sustainability and, consequently, the sustainable concrete concept. This work, it was used data from a questionnaire survey conducted previously with a group of professionals from the concrete industry about aspects related to sustainable concrete. The respondents’ background was categorized by the association in Contractors, Academic, Owners, and Materials. The current study utilized cluster analysis by using Agglomerative Hierarchical Clustering to form groups aggregated by similarities of opinions. Weights based on the stakeholders’ perspectives were calculated from the cluster’s groups. Also, different mixes designs containing various wastes and recycled materials were evaluated through indicators by using multi-criteria analysis to find the most sustainable option. The integration of the weights and the mixes designs provided a more sustainable mix design based on the cluster groups’ perspectives of sustainability and sustainable concrete aspects. This evaluation provides a more accurate answer of the most sustainable concrete mix based on a group of stakeholders’ opinions and it can help to better describe their needs and perspectives, culminating in a step forward to the sustainability evaluation of concrete.

Ludmila Soares Carneiro, Michael Henry
Research on the Industry Acceptance and Promotion Path of Interim Payment in Civil Engineering Projects

The problems of interim payment in civil engineering projects are still very prominent. However, the current research on the problems is insufficient. In addition, Chinese enterprises rarely use interim payment but mostly use completion settlement, resulting in poor contract performance, more disputes, and low control of the construction payment process. Once China fulfills all WTO commitments in the future, the scope of open contracting of civil engineering projects will be expanded shortly, and the payment problems in China will have an impact on enterprises worldwide. Thus the payment problems should be paid attention to and solved as soon as possible. The Chinese government has issued policy documents to comprehensively implement the interim payment. This study aims to measure the industry acceptance of interim payment and to identify the critical reasons that hinder its implementation. This study first established an acceptance model based on the technology acceptance model. Then this study identified 25 factors influencing the acceptance of the interim payment through literature review and expert interviews. By using a structural equation model and conducting a questionnaire survey, this study validated the hypotheses with 131 valid responses. The results showed that private investment projects have a higher acceptance of the interim payment than government investment projects. However, the overall acceptance is not high. The critical reasons that hinder the implementation of the interim payment are that it is not easy to learn and use, and the new benefit distribution mechanism has not been formed. Therefore, government authorities should enhance policy support, promote training, and promote the formation of a new benefit distribution mechanism. The results contribute to the body of knowledge on cost control and provide practical suggestions for improving the acceptance of the interim payment.

Lei Zhu, Hui Xiong

Advances in Vibration Mitigation of Long-Span Bridges and High-Rise Structures

Damping Effects of Cable Dampers on Girder Vibrations of Cable-Stayed Bridges

Cables and the girder of long-span cable-supported bridges are subjected to problematic vibrations (e.g., vortex-induced vibrations), owing to low structural vibration frequency and damping. It is a common practice to install dampers between cables and the girder to suppress cable vibrations in cable-stayed bridges. The attainable cable damping has been the focus of a number of previous studies assuming the bridge girder as a rigid support of the dampers. The damping effects of those cable dampers on bridge girder vibration have not been studied, while it has been observed that during (quasi-static or dynamic) bridge girder deformation cable dampers are deformed considerably in long-span cable-stayed bridges. Therefore, it is of interest to appreciate the damping effects of cable dampers on girder vibrations. Besides, vibration mitigation of bridge girder is also of practical significance. For this purpose, a finite element model (FEM) of an existing long-span bridge—the Sutong Bridge that is the first cable-stayed bridge in the world with a main span over 1000 m—is used for damping analyses. Particularly, the cables are divided into a number of link elements and cable dampers are included in the FEM. By eigenanalysis of the full model, damping of the structural modes dominated by girder vibrations is obtained with respect to the damping coefficients of the cable dampers. The variation of the damping ratio for varying damping coefficients is demonstrated and discussed. It is found that the cable dampers can increase the damping of the bridge girder. The results are useful for cable damper design considering both their damping effects on cables and bridge girders.

P. Sae-ma, L. Sun, L. Chen, Z. Liu
Design and Optimization of Viscous Damping Outrigger Vibration Reduction for Ultra-high Structures

Super tall buildings are wind sensitive structures. It has been a hot direction to study how to improve their wind-induced comfort. Viscous dampers are widely used in vibration reduction because of their high energy dissipation characteristics. In this paper, an optimal layout method of viscous damping outriggers is proposed to improve the layout efficiency of damping outriggers in mega frame core tube structure. Based on the energy consumption ranking of viscous dampers and the low coupling premise of outrigger area, the damping efficiency of each outrigger area position can be obtained by analyzing the fully distributed damping structure only once. Then, according to the contribution value of additional damping ratio of damping outriggers in each area, the optimal layout number and position scheme of damping boom are selected by comparing the target additional damping ratio. Through a simplified model, the rationality of the hypothesis and the efficiency and intuitiveness of the method are verified; Finally, the method is applied to a practical engineering case.

Jie Yao, Xin Zhao
Double-Track Nonlinear Energy Sink for Dynamic Response Control in Wind Turbine Towers

With the trend of larger wind turbine rotors to utilize more wind energy, wind turbine towers are becoming consequently higher and more flexible. Thus, the dynamic response of towers appears more significant and needs to be controlled to avoid potential resonance and even damage. This paper proposed a new type of double-track nonlinear energy sink (NES) to explore its mitigation effects on dynamic response of wind turbine towers. Firstly, the double-track NES is designed with optimal parameters. Subsequently, dynamic response of the onshore wind turbine tower with the double-track NES installed are investigated experimentally in wind tunnel. A comparison of dynamic response of wind turbine tower with or without double-track NES control is presented to prove that the novel NES can rapidly attenuate the response of the underlying tower, for both in-flow and cross-flow directions. This study reveals the potential application of the double-track NES in dynamic response control of wind turbine tower.

Dong Li, Zheng Yu Zhang, Xuhui Zhang
Multi-stage Objective Algorithm for Accelerating the Structural Optimization of Tall Building Structures

For large or complex structures, due to the large amount of design variables, structural optimization often takes too much time. This paper studies how to define the appropriate component size in a specific structural component, so as to achieve the optimal distribution of structural materials and achieve the most economic design of the structure on the premise of meeting the safety indicators of the structure. Based on the traditional Bidirectional Evolutionary Structural Optimization(BESO) algorithm, multi-stage objective algorithm is developed to accelerate the structural optimization process. Taking a 10 story steel frame shear wall plane model as an example, the optimization aim stage is defined by the constraint redundancy values. And the rationality of the method is proved by the optimization results.

Xin Zhao, Gang Wang, Jie Yao
Optimal Design of Energy-Dissipated Substructure with Viscous Damper for High-Rise Building

In order to ensure that the damper can function normally under various levels earthquakes, and the energy-dissipated substructure will not be damaged under the additional force of the damper, it is necessary to make special design of the energy-dissipated substructure. At present, there is no mature design method of energy-dissipated substructure in the industry, which often leads to conservative design. Therefore, effective optimization design method is needed to ensure the normal function of damper under various levels earthquake with reasonable engineering cost. This paper proposes a performance-based design method of energy-dissipated substructure, which mainly involves the following four aspects: firstly, the performance-based seismic design method studies the reasonable performance objectives of energy-dissipated substructure members; Secondly, the internal force of elastic design under frequent earthquakes multiplied by the amplification factor is used to approximate the rare earthquake action, which avoids the cumbersome operation and low efficiency elastoplastic analysis; Thirdly, some other optimization methods of energy-dissipated substructure are studied, such as using higher strength material to reduce the section and stiffness of substructure members, so as to avoid torsion and stress concentration in the substructure; Fourth, a new idea of damper design is proposed. By using the damper with valve, only the elastic analysis under frequent earthquakes is needed. When the pressure generated by the valve exceeds the maximum locking force under rare earthquakes, the special relief valve opens to protect the damper from damage during rare earthquakes. Finally, the effectiveness of this method is verified by a simplified structure model. The results show that this method can effectively simplify the design process of energy-dissipated substructure, improve the analysis efficiency, and has practical engineering value.

Daohang Hu, Xin Zhao
Optimization of Damped Outriggers for Maximizing Multimode Damping of Long-span Bridges for Vibration Suppression

Characterized by large flexibility and low damping, long-span cable-supported bridges are subjected to wind-induced vibrations. Aerodynamic countermeasures might be no longer sufficient for vibration mitigation of such bridges. Therefore, it is important to install dampers on bridges for supplementing damping. This study focuses on a novel strategy by using damped outriggers to control the rotation of the bridge deck at the junction points between the girder and the bridge tower or pier. Specifically, a vertical rigid arm is installed on the girder near the junction, and the end of the rigid arm is connected to the bridge tower through horizontal dampers. Through the damped outriggers, the angular displacement of the girders can be transformed into the linear displacement at the end of the rigid arm, and then the energy can be consumed by the horizontal dampers to suppress the vibration. Subsequently, a general design method for adding damped outriggers to long-span cable-supported bridges is proposed. At last, the Xihoumen Bridge with a main span of 1650 m is taken as an example for detailed dynamic analyses. A finite element model of the bridge with damped outriggers is established. The static analysis and eigen analysis are then carried out. The damped outriggers are installed at multiple positions, and the optimal damping coefficients of dampers are discussed for multimode vibration mitigation so that the damping ratio of modes in which vortex-induced vibration (VIV) occur are relatively large. The results show that through the proposed optimization method, the strategy can provide relatively large damping ratio for VIV modes, which is of great practical significance.

Zhanhang Liu, Lin Chen, Limin Sun

Intelligent Shield Tunnelling

A Preliminary Review of Digital and Intelligent Cutterhead Management and the Enabling Technologies in Shield Tunnelling

The shield machine is large-scale construction equipment with an intelligent and highly complex system for tunnel excavation. The process of managing and controlling the shield cutterhead is significant, especially for large-size shields. It is a complicated and challenging process but indispensable, thus a digital shield cutterhead management system is needed. With advances being made in artificial intelligence (AI), the capability exists to automatically manage and control large-size construction machines. The corollary developments in artificial intelligence have stimulated a wealth of research in construction to examine its potential application to practice. Firstly, the paper reviews the state of the art and practice of digital shield cutterhead management technologies. Then, with consideration of the advances made within machine learning and digital twin, research challenges, which impede further applications of AI in cutterhead management for super-size shields, especially in composite geological stratum, are analyzed and identified. Finally, future works regarding how to promote the application of these enabling technologies in shield cutterhead management are proposed.

Ziwei Yin, Gang Li, Hanbin Luo, Zhengjun You
Data-Driven Safety Assessment for Shield Tunnel Excavation: Interoperability Between Parametric Modeling and Numerical Simulation

Shield tunnelling is of high risk due to the significant uncertainties of construction parameters and underground space. Numerical simulation technique is an indispensable process to evaluate the risks during shield tunnel excavation with reasonably low cost. Benefiting from the application of parametric modeling technology such as building information modeling (BIM), the interoperability between a parametric model authoring tool and numerical simulation program has been developed in a tunnel project, which can optimize engineering design and enhance risk assessment of engineering construction. An extensive literature review is also conducted to describe the data-driven safety assessment of shield tunnel excavation that carried out by the interoperability approaches, starting from the four aspects: parametric modeling for shield tunnel excavation, deterministic safety assessment (DSA) driven by basic design data, probabilistic safety assessment (PSA) supported by statistical data and real-time analysis (RTA) conducted by monitoring data. The pros and cons of the prior art are preliminarily discussed.

Ping Xie, Gang Li, Hanbin Luo, Xiao Yang
A Dynamic Model of Machine Learning and Deep Learning in Shield Tunneling Parameters Prediction

Tunnel boring machine (TBM) is widely utilized in large cross-section tunnel excavation with high permeability soil conditions. During the shield tunneling process of TBM, dynamic prediction of driving parameters including advance rate and cutterhead torque is required. This study establishes a dynamic prediction model (DPM), LSTM-XGBoost, based on machine learning and deep learning algorithm framework incorporating with wavelet transform, long short-term memory method (LSTM) and extreme gradient boosting method (XGBoost). The proposed DPM can predict TBM-driving parameters in advance and adjust parameter weight in order to optimize operation. Moreover, the generalization ability of the proposed DPM is compared with traditional machine learning algorithms such as support vector machines (SVM) based on the data obtained in a practical tunneling project. The comparison results reveal that the LSTM-based DPM is suitable for prediction of time-series data.

Ruohan Wang, Guan Chen, Yong Liu
Hybrid Model for Predicting Average Cutter Wear in TBM Excavation

The complex interaction between soil and TBM cutters makes it hard to estimate the cutter wear precisely and reliably, especially for the composite strata (inhomogeneous geology). In this study, a tunnel that crosses the composite strata, Sanyang Road Highway-railway Tunnel (SRHT) in China, is introduced. A process-based mechanism is used to illustrate the conversion from contacting asperities to wear debris and deduce a wear calculation formula. For the wear estimation, how to fast determine pending wear coefficient in formula to guarantee prediction accuracy remains a challenging issue. In order to ascertain the wear coefficient under different conditions, this study proposed a hybrid model for incorporating mechanism and data-driven model. The results show that (1) good performance in prediction accuracy, the R2 and RMSE value of hybrid model are 0.8317 and 0.00756, respectively; and (2) high robustness under different geological conditions and data noises, which ensure the applicability of the proposed model in real engineering case. This research contributes to (1) the state of knowledge by proposing a universal hybrid prediction model that can incorporate the physical mechanism model and data-driven model, and (2) the state of practice by providing a cutter wear prediction model to provide decision support for the cutter replacement scheme.

A. Li, G. LI, C. Wang, W.-L. Liu
Optimal Control of Operation Parameters During EPB Shield Tunnelling Based on Artificial Neural Network Model

Shield machine is a widely utilized excavation equipment in the tunnel construction process, especially in the complex geological environment. Optimal control on the operation parameters is vital to maintain the quality of the tunnel construction and to avoid the serious sinkhole hazards. This study therefore established an artificial neural network (ANN) model to predict the total thrust force and the advance speed of the earth pressure balance (EPB) shield machine. A set of data from the seventh section of Wuhan metro line six in China was utilized to train the ANN model. Then, the parameter filtering procedure was performed to identify the key factors controlling the tunnelling performance and hence to improve the prediction accuracy. Finally, the established ANN model was adopted to predict the operation parameters of shield machine (i.e., total thrust force and advance speed). The good agreement between the predicted and measured data demonstrates the precision and advantage of this ANN model, which poses a guiding significance in dynamically identifying the environmental conditions and adjusting the operating parameters of an EPB shield machine during tunnelling.

Xuejian Chen, Qing Kang, Yong Liu
Intelligent Decision Framework of Shield Attitude Correction Based on Deep Reinforcement Learning

Shield attitude is an important control element in the construction of shield projects. Due to the complex shield construction environment and the difficulties of shield machine operation, shield attitude control often has lag and inaccuracy. For the problem of shield snaking motion caused by untimely and inaccurate shield attitude adjustment, scholars have proposed some attitude prediction models and fuzzy PID control models based on machine learning and deep learning. However, these models are highly environment-dependent and require expert priori knowledge, making it difficult to predict or control the shield attitude in time when the construction environment changes. To address the shortcomings of these models, this paper proposes an intelligent decision framework of shield attitude correction (IDFSAC) based on deep reinforcement learning. This framework is able to interact with the construction environment and adaptively find the best correction and control strategy. The effectiveness of IDFSAC is experimented using a shield construction simulation system. Results reveal that the framework can adapt to the changes of construction environment and realize automatic and intelligent correction and control of shield attitude.

J. Xu, J. F. Bu, L. G. Zhang, J. Zhang, K. F. Li, S. M. Liu

Composite Materials and Structures

Behavior of Bamboo Scrimber Beam-Column Joints with Bolted Steel Angles and T-Stubs

Bamboo scrimber is a new composite material with good mechanical properties. It can be used in structural members such as beams and columns. Different joints have been developed to connect bamboo scrimber beams and columns. This study presents experimental tests of bamboo scrimber beam-column joints between I-beams and box columns by using bolted steel angles and T-stubs. Four joints were tested under monotonic loading to determine the moment resistance and rotational capacity. Test results showed that the joints exhibited semi-rigid characteristics when subjected to bending moment. For the joint with T-stubs, the load-bearing capacity was 38% greater than that of the joint with steel angles, and the initial stiffness of the former was 94% higher than that of the latter. However, the ultimate rotation of the joint with T-stubs was slightly lower than that with steel angels. Finally, Deierlein’s model was used to simulate the bending moment-rotation curves of the joints, and the simulation results were compared with the experimental results which showed good accuracy.

Jun Xiong, Shu-Rong Zhou, Shao-Bo Kang
Experimental Study on the Behaviour of CFST Columns with Steel Slag Concrete Under Axial Compression

Steel slag, a waste by-product in the steel industry, is now becoming increasing popular to replace natural coarse and/or fine aggregates in making concrete, which offers a sustainable solution in relieving the environmental problems due to huge depletion of natural aggregates and disposal of abundant slag. Extensive research studies revealed that steel slag concrete had superior strength and stiffness. However, the unique chemical composition of steel slag may cause unsoundness problem in the concrete, which scared the engineers in using it. To solve the problem, steel slag concrete-filled-steel-tube (SSCFST) column was proposed. By confining the steel slag concrete with steel tube, the concrete’s expansion would activate larger confining stress and thus enhancing the overall behaviour of the column. A total of 6 SSCFST column specimens were fabricated and tested under uni-axial compression. The major testing parameters were the steel tube diameter to thickness ratio, the steel slag coarse/fine aggregate replacement ratio. Results revealed that by replacing natural coarse/fine aggregate with steel slag coarse/fine aggregate, the flowability of concrete reduced since steel slag was more angular and had higher water absorption and porosity. Besides, the compressive strength increased due to the cementitious property of steel slag. By filling the steel slag concrete into steel tube, the SSCFST column showed superior strength, stiffness and ductility owing to the composite action. The axial load was enhanced by 17% to 24% compared with the squash load (steel yield load plus concrete crushing load). With steel slag aggregate, the axial load was larger than that with natural aggregate only.

Y. H. Lin, Y. Y. Jin, J. C. M. Ho, M. H. Lai
Experimental Study on the Post-fracture Property of Laminated Glass

Laminated glass commonly consists of two glass layers and one interlayer, which is widely used in important and high-rise buildings as safety glass. The glass fragments are attached to the interlayer under extreme load and prevent the glass fragments from splashing to hurt residents. In this paper, the post-fracture performance of Polyvinyl-butyral (PVB)-laminated glass with medium (BG R15) and high (BG R20) adhesion grades, and SentryGlas® (SG)-laminated glass were studied through Random-Cracked Tensile (RCT) tests. The influence of key parameters, including loading rate (0.00005 m/s, 0.005 m/s, 0.1 m/s, 0.5 m/s, and 5 m/s), glass fragment size (large fragments, medium fragments, and small fragments) were investigated in this test. Compared with PVB-laminated glass, SG-laminated glass specimen offers higher load-bearing capacity. However, the deformability of SG-laminated glass specimen is lower than that of PVB-laminated glass specimen. With the increase of loading rate, the bearing capacity increases for three laminated glass specimens. However, the deformation capacity of PVB specimen reduces with the loading rate. The bearing capacity of PVB specimens decreases with the decrease of fragment size, and the deformation capacity increases with the decrease of fragment size. The influence of fragment size on the bearing capacity and deformation of SG specimen is not obvious. Moreover, the deformation capacity and energy dissipation capacity of BG R15 specimens are significantly higher than those of BG R20 and SG specimens. This study is of great significance in guidance for selecting interlayers with energy consumption requirements under extreme loads (such as explosion and impact).

Zhifei Chen, Suwen Chen, Xing Chen
Experimental Study on the Uni-axial Behaviour of MSCFST Columns Considering Concrete’s Wet Packing Density

Manufactured sand (MS), which is produced by mechanical crushing of rock depositions or construction wastes, has been adopted as one of the possible river sand (RS) succedaneum to make ‘Greener concrete’. In this study, the possibility of the application of MS concrete in concrete-filled-steel-tube (CFST) column has been investigated. A total of 5 CFST columns with MS partially or totally replacing RS have been prepared and tested under uni-axial compression. The main parameter was the MS replacement ratio (0%, 25%, 50%, 75% and 100%). From the experimental study, it is clear that by replacing RS with MS, the fresh and hardened properties of concrete varied. Besides, all the CFST columns failed by local buckling and as the MS replacement ratio increased, the local buckling seems more irregular. Moreover, the CFST columns showed different load-strain behaviour as the MS replacement ratio changed. The concrete’s wet packing density (WPD) is a better indicator than MS replacement ratio on the strength of concrete and the load-carrying capacity of CFST columns. In general, maximizing the WPD would enhance the strength of plain concrete and significantly improve the load-carrying capacity of CFST columns.

J. H. Mo, M. R. Zeng, S. J. Yang, J. C. M. Ho, M. H. Lai
Load-Carrying Capacity of CFST Columns: Current Design Rules Assessment

Concrete-filled-steel-tube (CFST) column, which consists of a hollow steel tube in-filled with concrete, has been widely adopted in the construction of infrastructures, tall buildings and bridges owing to its superior strength, stiffness and ductility contributed to the composite action. Currently, design equations have been proposed to predict the load-carrying capacity of CFST columns in design codes such as American Concrete Institute (ACI), American Institute of Steel Construction (AISC), Chinese Standard and Eurocode 4 (EC4), etc. However, as reported by some research studies, these codes could not predict the load-carrying capacity of CFST columns accurately, especially when the material strengths of other parameters exceeded their limitations specified in the codes. Besides, few studies have been carried out to compare the serviceability between different design codes with different parameters systematically. To fill up the above research gap, this study provides a comprehensive study to evaluate the applicability of the above current design codes. To start with, an experimental database consisting of 177 test results of CFST columns was assembled. Then the design equations stipulated in the current design codes were briefly introduced. Lastly, the load-carrying capacity obtained from the database was compared with the design strength. Results indicated that the design strengths predicted by ACI and AISC were the lowest since the confinement effect was not considered. Among all the above codes, EC4 made the most accurate prediction.

X. L. Ou, J. C. M. Ho, M. H. Lai
Study on Mechanism of Pore Modification by Polymer Particles

In recent years, deterioration of concrete structures has become a problem, and requires maintenance and repair. The cross-sectional repair method is frequently used to repair deteriorated structures. The material used in this method must have good adhesion to concrete and durability against the deterioration factors such as carbonation, chloride penetration and water permeability. In ordinary polymer cement mortars, the polymer particles bond together and make a polymer film, which improves the mass transfer resistance. Therefore, it is often used as a cross-sectional repair material. On the other hand, new developed core-shell polymer particles have dispersibility and two-layer structure of core and shell. In some cases, the addition of this polymer has been shown to have very high mass transfer resistance to water. However, the mechanism of the performance improvement has not been understood yet. The improvement in mass transfer resistance is thought to be due to the modification of the pore, which is a mass transfer pathway. In this study, we measured the porosity and conducted mass transfer resistance, and compared core-shell polymers with various materials which densifies the pores. For example, ordinary polymers that has films and silica fume which has a pore-filling effect with fine particles. In addition, by comparing several tests and expressing the state inside the pores, we investigated the mechanism of improving mass transfer resistance when core-shell polymer is added.

R. Yahiro, T. Kanda, K. Nishimura, T. Iyoda

Progressive Collapse and Ultimate Structural Resistance

Effects of Modeling Methods of RC Diaphragm on the Behavior of Steel Staggered Truss Framing Structures

Steel staggered truss framing (SSTF) structures have the merits of large lateral stiffness, flexible space, less steel consumption and fast construction. In a SSTF structure, the diaphragm needs to transmit large in-plane shear forces from the staggered truss in addition to resist gravity loads when subjected to lateral earthquake actions. The mechanical behavior of the diaphragm and its influence on the behavior the structure deserve research attention. Three modelling methods of the reinforced concrete diaphragm, based on rigid membrane elements, shell elements, and multi-layer shell elements, were used and compared in SAP2000 through seismic response spectrum analysis and pushover analysis. The drift ratio, development of plastic hinges, internal force of members and floor deformation, obtained from the different modelling methods, were investigated and compared. The results showed that the modelling method did influence the behavior of SSTF structures.

Zexiang Li, Dan Gan, Xuhong Zhou
Finite Element Analysis of Bonded-PT Slab Column Connections Under Lateral Load

In this paper, the numerical results compared with the testing results to calibrate a model. The parameter in ABAQUS was adapted to proper for the simulate model in linear and nonlinear behavior. From the study realize the importance of gravity shear ratio (Vg/Vo) is the main parameter effect on the performance around the critical section around slab- column connection under lateral load. The shear stress that occurs around the critical section was depended upon by the gravity load varied according to usability of the structure. When shear stress has varied. The effect on the gravity shear ratio (Vg/Vo) of performance will be different. In the numerical simulation, the gravity shear ratio can input vary data in ABAQUS program.

K. Kingkokgruad, U. Prawatwong
Numerical Study of Prestressed Concrete Girder-Deck System with Variable Reinforcement and Span-depth Ratios

AASHTO Type III prestressed girder is one of the most widely used girder types to carry highway bridge decks. However, very few quantitative studies have been conducted to study the effect of span-to-depth ratio (L/d) on flexural behavior of AASHTO Type III prestressed girder-deck system via finite element analysis. This paper presents the results of numerical analysis investigating the effect of two primary variables (reinforcement ratio and span-to-depth ratio) on the flexural properties of AASHTO Type III prestressed girder using finite element software Abaqus. A detailed finite element analysis (FEA) model was developed and verified against the relevant experimental data performed by other researchers. The analytical results showed good agreement with the experimental results. Based on the verified FE model, analyses were performed using variables including three critical span-to-depth ratios (L/d) of 10, 15 and 20 and prestressing reinforcement ratios (ρ%) of 0.101, 0.126 and 0.151. Ultimate strength, stiffness, and ductility of the prestressed Type III girder were investigated. The nonlinear finite element results demonstrated that different span-to-depth ratios can significantly affect flexural performance. It was found that a higher span-to-depth ratio has a lower stiffness and ultimate strength than a lower span-to depth ratio. However, the ductility decreases with the increase of the span-to-depth ratio. In addition, under the effect of prestressing reinforcement ratio, the impact of span-to-depth ratio on flexural performance increases.

H. Ni, R. S. Aboutaha

Disaster Mitigation

Flexural Performance of Mill Cut Steel Fiber Reinforced Concrete Beam Degraded by Mild Corrosion

Corrosion of steel occurred in the reinforced concrete structures is one of the most significant causes of deterioration and reduction of the loading capacity of the reinforced concrete structures. Applying fiber extended the initiation stage and postponded the crack propagation stage of corrosion process in RC structure. Therefore, this research aims to evaluate the effectiveness of utilizing steel fiber reinforced concrete (SFRC) for its application in a chloride environment. To investigate the flexural behavior of the corroded SFRC beam under static loads, the concrete with the water-to-cement ratio of 0.4 containing steel fibers of 0, 0.5%, 1.0%, and 1.5% were used. The impressed current method was applied to accelerate the corrosion of steel to reach 5% by applying the constant current of 250 µA/cm2 within 38 days. The flexural strength of eight beams having an identical section of 150 × 200 mm and a length of 1400 mm were examined under a four-point bending test. The experimental results showed that the presentation of mill cut steel fibers significantly influenced the flexural performance of the corroded SFRC beams. Corrosion of steel led to a more significant reduction of load capacity of the RC beams, whereas the beam containing the steel fiber remained the ultimate or yield load capacity. Fibers take account for compensating the flexural strength of the structure due to the loss of cross-section of the steel bar by corrosion effect and limit the propagation of the width crack.

Khanh Minh Vo, Withit Pansuk, Thi Nguyen Cao, Hai Yen Thi Nguyen
Structures Under Blast Loads from Academic Research into Engineering Applications: Advances and Limitations

Recent increases in terrorist activities and accidental explosions, e.g., the 2020 Beirut blast or gas explosion event in the North-eastern city of Shenyang, China in 2021, have caused devastating consequences and imposed significant threats to public safety and economic development. Together with direct primary effects from explosive events, i.e., primary shock pressure and/or secondary fragments, the indirect secondary effects caused by blast events such as the progressive collapse of structures are also critical when resulting in more widespread significant losses. Therefore, critical infrastructure, e.g., government buildings, public transport infrastructure, petrochemical, and hazardous material storage facilities, need to be carefully considered under these extreme loading events in their design and operations. In current engineering practices, Single-Degree-of-Freedom (SDOF) is typically utilised to design structures under far-field blast events, whilst finite element (FE) analysis is adopted when considering close-in or contact blast scenarios. With the recent developments of material models under high loading rates, e.g., K&C concrete material release III or Continuous Surface Cap concrete model (CSCM), and fluid-structure interaction simulation technique, e.g., Arbitrary Lagrangian-Eulerian (ALE), the capability and application of FE analysis in the blast effect analysis of structures under close-in blast events have increased considerably. Although FE and SDOF analyses developed in previous studies contribute to providing reasonable predictions on the blast performance of structures, there are several limitations that need to be resolved in order to increase the reliability of the analysis techniques employed to ensure accurate prediction of structural behaviour to these complex response modes. Typical studies normally focus on the structural member responses, i.e., flexural or shear responses, while connection forces between structural members have not been fully investigated. The accuracy of the FE model and SDOF in predicting the reaction at structural supports is still unknown. Moreover, the failure of concrete structures under close-in blast events, e.g., concrete spalling and breaching or fragment velocity, is not considered to be accurately predicted by the abovementioned methods. Advances and limitations of those analysis methodologies are to be discussed in this study.

Tin V. Do, Asher Gehl
Free and Forced Vibration Characteristics of Functionally Graded Sandwich Beam with GPL-Reinforced Porous Core

In this report, the dynamic response of a functionally graded graphene platelets porous (FGP-GPL) sandwich beam composed of two functionally graded material (FGM) face sheets and an FG porous core reinforced with graphene platelets is investigated. Uniform/non-uniform distribution patterns of internal pores and GPLs along the thickness direction are considered. The governing equations are derived from Lagrange’s equations in the framework of quasi-3D beam theory. Ritz method based on polynomial trial functions is utilized to discretize the equilibrium equations into a matrix form and then solved by Newmark's constant average acceleration method to obtain the time-dependent response. The accuracy of the presented methodology is confirmed by comparison with analytical solution and with results available in the open literature. Parametric studies are conducted to highlight the effect of porosity coefficient, porosity and GPL distribution patterns, volume fraction index, GPL weight fraction, boundary supports on the dynamic characteristics of the sandwich beam.

Tran Quang Hung, Do Minh Duc, Tran Minh Tu

Engineering Design and Dynamics Structural Response

Ballastless Track Support Deterioration Evaluation Using Machine Learning

Ballastless tracks have been widely used for highspeed rail systems globally since their maintenance is relatively minimal. However, support deterioration right beneath the in-between slabs’ connectors has been usually reported and quite well known in the industry. Any water ingress can quickly undermine the condition of cement-stabilized soil that supports the track slabs. It is thus very crucial to very early detect the impaired condition of the slab supports since mudded support can result in poor ride quality and eventually endanger highspeed train operations. Therefore, the ability to predict the deterioration of track slab supports is highly beneficial to predictive and preventative maintenance in practice. In this study, track slab support stiffness is considered as a precursor to identify the severity of deterioration. The nonlinear FE models, which were validated by field measurements, have been used to populate data in order to develop machine learning models capable of evaluating the track support deterioration. Axle box accelerations are adopted in a form of datasets for machine learning models. Parametric studies have yielded a diverse range of datasets considering the train speed variations, train axle loads, and irregularities. The results demonstrate that the machine learning models can reasonably diagnose the condition of the track slab supports. The outcome reveals the potential of machine learning to evaluate ballastless track support deterioration in practice, which will be beneficial for railway maintenance.

Jessada Sresakoolchai, Ting Li, Sakdirat Kaewunruen
Bursting Effects in Prestressed Concrete Sleepers at Different Prestressed Levels

The railway sleeper is an important part of the railway track system, which distributes the wheel load to the substructure. The prestressed concrete sleeper is the most commonly used type around the world, which is usually designed for 50 years of service life. Prestressed concrete sleepers experience various environmental and loading conditions. Meanwhile, the material properties degrade with time. The premature failures of prestressed concrete sleepers could happen and result in a series of problems especially cracking. Tensile strength of prestressed concrete sleeper is much lower than compressive strength like other concrete structures. During service, impact loads could cause cracking in rail-seat or centre area of a prestressed concrete sleeper. Therefore, it is important to understand tensile stress at different prestressed levels. This paper presents a tensile stress assessment method for prestressed concrete sleepers. The outcomes of this paper will improve the concrete sleeper maintenance and inspection criteria.

Dan Li, Sakdirat Kaewunruen, Ruilin You
Plate Thickness Distribution Estimation of a Belt Conveyor Support Structure Member Based on Cross-Sectional Vibration Modes Using Machine Learning

Belt conveyor support structures are usually under a corrosive environment due to the dust accumulation from the belt conveyor. The corrosive damage may cause severe safety problems. Therefore, it is necessary to develop a specific health monitoring method for this kind of structure. Recently, Cross-Sectional vibration Mode (CSM)-based methods have been investigated. CSM has been shown to have sensitivity to damage to a member of a belt conveyor support structure. However, the quantitative evaluation of the damage has not yet been realized. In this paper, a machine learning method is applied to estimate the spatial distribution of plate thickness of the member. To create a large and precise CSM dataset efficiently, a new CSM indicator is proposed. To validate the method, the CSMs of multiple members are measured, and discrete plate thickness distributions of each member is estimated using a trained machine learning model. The result shows high accuracy.

Daichi Ogawa, Yaohua Yang, Tomonori Nagayama, Sou Kato, Kazumasa Hisazumi, Tomonori Tominaga
Simulation and Simplified Method Study on Seismic Collapse of Core-outrigger Structures

The seismic collapse resistance of super high-rise structures is very important. Based on the shaking table test of a core-outrigger structure, a multi-scale finite element model is established for collapse simulation analysis; IDA static equivalent method is proposed to evaluate the collapse resistance of the model on the assumptions about lateral force distribution, capacity spectrum curve and collapse performance point; blind source separation method is used for data-driven damage detection to reveal the earthquake collapse mechanism and evolution process of super high-rise structures. The results show that the response time history of the multi-scale model is in good agreement with the experiment, and can simulate the lateral collapse of the structure caused by the local buckling of the column; IDA static equivalent method is efficient and accurate for evaluating the seismic collapse resistance of the core-outrigger structure; blind source separation method can extract the information of time and location of structural damage only from structural response data.

Y. Liu, J. Huang, F. F. Sun, G. Y. Chen

Advanced Transportation Infrastructure and System

Application of Ai-based Deformation Extract Function from a Road Surface Video to a Road Pavement Condition Assessment System

In Japan, there is a concern that civil infrastructure will rapidly age in the near future. This study focuses on asphalt road surfaces, which are typically renovated every 10 years depending on the amount of traffic and roadbed properties. Existing MCI (Maintenance Control Index) measurement systems come at a high cost to local governments and are not efficient in allowing engineers to detect cracks and deficiencies. New road pavement assessment systems, as developed by our research group, are needed to ensure sustainable road maintenance and management. Pavement surface evaluation system development involves the use of a video camera and a 3D motion sensor, which can be used for simple and low-cost inspections. However, 3D motion sensors can only capture acceleration. Because of this, they can only be used to illustrate the roughness of the road surface, not to detect cracks. In this study, to utilize road surface video recorded while driving, we have developed a method of automatic extraction of deformations by an AI object detection function. This function specifically serves to extract cracks, joints, manholes, and repair marks detections from the surface video. However, in using this function, the accuracy for detecting cracks was less than 40% (Shiga et al. 2020). In this study, we aim to apply this method to detect deformations and suggest annotation rules for improving the accuracy of crack detection, as well as overall accuracy. To discuss the accuracy of detecting cracks and other deformities, cracks are divided into different types and deep learning is performed. In addition, we enlarged images of the cracks.The results of this study show that the AI object detection function for cracks is made more accurate by utilizing annotation rules and making a learning data rule set divided by the crack type classification.

Hisao Emoto, Miori Numata, Atsuki Shiga
Assessing the Sustainability Characteristics of Modified Asphalt Concrete

The increasing concern on impacts of various sectors to sustainability has prompted the transportation sector to improve efforts on enhancing sustainability through various tools. Whilst extensive research has currently been done on various innovative pavement materials, their impact on sustainability is still yet to be properly understood and quantified, therefore a need to analyze the sustainability characteristics of various modified bituminous mixes on the sustainability of Asphalt Concrete. Asphalt Concrete consumes high volumes of natural resources and is energy intensive henceforth affecting sustainability. Warm Mix Asphalt (WMA), Crumb rubber modified Asphalt (CRMA), Reclaimed Asphalt Pavement (RAP) and Waste Plastic Asphalt (WPA) are all mixes that incorporate additives or recycled materials to negate the negative environmental impacts of conventional Asphalt Concrete and are therefore associated with improved sustainability. Sustainability indicators such as Energy Consumption, Green House Gas emissions, Human Toxicity and Cost Implications as evaluated in Life Cycle Analysis (LCA) from various literatures were used to compare the impacts of using the alternatives through relationship graphs. The results show that lowering the temperatures of production by about 19–63 °C in the case of WMA and replacing between 2 and 100% of either binder or whole mix with recycled material in the case of RAP, CRMA and WPA lowers most indicator values vis-à-vis baseline produced values, therefore achieving not only higher environmental benefits but in addition proving to be good alternatives that perform similar or better than virgin mixes. This notwithstanding, there are limits to the quantity of additives or recycled material that is used to modify the mixes due to their effect on overall mixture performance requirements. In conclusion a quantitatively based positive sustainability effect of the considered alternatives can be seen therefore proving that these alternatives when properly engineered can be used to improve sustainability goals in the road sector.

G. Muna, M. Henry
Factors Affecting the Deterioration of Bituminous Pavements in Khyber Pakhtunkhwa Province, Pakistan

It is essential to study the factors that lead to the deterioration of bituminous pavement in order to prepare an effective maintenance plan. In developing countries, like Pakistan, a huge amount of budget is spent every year on the rehabilitation of road network due to the absence of an effective maintenance plan. The amount can be reduced by formulating the maintenance plan which will be based on the factors that cause deterioration of pavement surface. The objective of this study was to identify the factors which cause the deterioration of bituminous pavements in the Khyber Pakhtunkhwa province of Pakistan. The research was based on provincial highway network data, collected from the local highway department. The data consisted of 23 road characteristics, out of which 16 nos. Pavements’ condition-related data were selected. The pavement conditions of the provincial highways network of Khyber Pakhtunkhwa are divided into good, fair, and poor depending on the IRI index and vehicular speed. To scrutinize the factors that affect the pavement condition, cross-tabulation analysis was performed. It was concluded through analysis that among different factors, overloading, poor drainage, and pavement terrain had a major impact on the deterioration of bituminous pavements. Based on the results, recommendations were provided to highway engineers for prioritizing the pavement projects for a future pavement maintenance plan.

Azam Amir, Michael Henry
Investigation on Recycling Application of Waste Rubber Tyres in Concrete

Rational and sustainable disposing and recycling of waste rubber tyres (WRT) has become a challenge with their numbers increasing and accumulating. According to statistics, the cumulative annual generation of WRT is about 1.5 billion; they cannot be degraded and are difficult to recycle. WRT was generally buried in the landfills, stacked in open storage, or used as fuel; which not only pollutes the environment but also wastes resources. The application of waste rubber powder in concrete not only improves the ductility of concrete but provides a new solution to the problem of waste rubber pollution. However, the workability and mechanical properties of concrete are greatly affected due to the poor compatibility between rubber particles and the cement matrix. To improve these weaknesses, a novel method to modify WRP by combining the organic and inorganic mixed slurry coating and filling effect was proposed in this study. The particle size distribution of rubber particles before and after modification, the effect of rubber particles on hydration heat and rheology of cement mortar, and interfacial bonding between rubber particles and cement matrix were explored. The compressive strength and splitting tensile strength of concrete with WRP and modified WRP (MRA) were determined. The results demonstrate this modification method was very effective, and the structure and properties of WRP were significantly improved. Under the same volume replacement percentage, the compressive strength and splitting tensile of concrete increased by 70.0% and 46.1%, respectively. The cavitation phenomenon between rubber particle and cement matrix disappeared, and the interface bonding was significantly improved.

Shengtian Zhai, Yunsheng Zhang, Laibao Liu
Proceedings of The 17th East Asian-Pacific Conference on Structural Engineering and Construction, 2022
herausgegeben von
Guoqing Geng
Xudong Qian
Leong Hien Poh
Sze Dai Pang
Springer Nature Singapore
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