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2024 | Buch

Proceedings of the Canadian Society of Civil Engineering Annual Conference 2022

Volume 3

herausgegeben von: Rishi Gupta, Min Sun, Svetlana Brzev, M. Shahria Alam, Kelvin Tsun Wai Ng, Jianbing Li, Ashraf El Damatty, Clark Lim

Verlag: Springer Nature Switzerland

Buchreihe : Lecture Notes in Civil Engineering


Über dieses Buch

This book comprises the proceedings of the Annual Conference of the Canadian Society of Civil Engineering 2022. The contents of this volume focus on specialty conferences in construction, environmental, hydrotechnical, materials, structures, transportation engineering, etc. This volume will prove a valuable resource for those in academia and industry.



Structural Specialty: Timber Structures

Experimental Evaluation on Nail-Laminated Timber (NLT)—Steel Fiber-Reinforced Concrete Composite Beams with Notch Connections

In North America, timber–concrete composite (TCC) floor system is gaining increasing interest in recent years thanks to their superior structural performance and low self-weight. Notched connections are a feasible and economical shear connecting solution for panel-type TCC floors. However, the concrete layer is prone to cracking under bending due to stress concentration around notches, which could lead to a brittle failure pattern and a decrease in the load-carrying capacity of the TCC floors. To address this issue, in this study, five groups of nail-laminated timber (NLT)–concrete composite beams were fabricated with varying notch depth, number and locations of notches, and ratios of thickness. The concrete layer was reinforced with steel fibers as a potential solution to mitigate the formation of cracks in the notches. Three-point bending tests were conducted to examine their bending performance. The results showed that the bending capacity of specimens is highly related to the ratio of the thickness and the number of notches so that the load-bearing capacity and stiffness of group 5 with the thickness ratio of 1:1 increased 34.6% and 49.4%, respectively, in comparison to reference group.

Hamidreza Chaboki, Lei Zhang, Jianhui Zhou, Thomas Tannert
Assessment of the Lateral Bearing Capacity of Traditional Walls Made of Timber Planks

Evaluation of the structural capacity of existing buildings is a key component in the seismic risk assessment process to estimate damage and socioeconomic losses due to earthquakes. In Eastern Canada, a large number of traditional residential buildings were built between 1860 and 1915 using a mixed structural system of unreinforced masonry «URM» and wood. The lateral stability and resistance of several of those traditional buildings rely on the behaviour of the peripheral walls made of timber planks covered by a brick veneer. These traditional walls, called “carrés de madriers”, are composed of timber planks, stacked horizontally between two wood posts delimiting panels between the wall openings. The lateral resistance is provided by the interaction and friction mechanisms between the horizontal timber planks and their interaction with the vertical wood posts. The main objective of this paper is to present: (1) a structural and mechanical characterization of a typical wall and (2) an evaluation of the lateral capacity using an analytical model and a finite element (FE) model. The analytical model is derived from the literature and used to estimate the maximum lateral displacement/resistance for this type of walls when subjected to in-plane lateral forces. In addition, major outcomes of a FE numerical investigation carried out on a single wood panel with the software ABAQUS© are discussed for different loading conditions (i.e. in-plane lateral and vertical compressive loads). Recommendations are given to improve the FE model especially the modelling of the connections between the horizontal and vertical elements.

Mohamed Hassen Kraiem, Amar Khaled, Marie-José Nollet
Validation of Proposed Analytical Model and Design Procedures for Multi-panel CLT Shearwalls Through Experimental Investigation

Multi-panel CLT shearwalls are expected to provide more flexibility and energy dissipation than single-panel walls, mainly due to the contribution of the vertical joints between panels. Despite several analytical models and design approaches being proposed in the literature, timber design standards provide limited guidelines on the lateral and capacity-based design approaches for CLT shearwalls. This shortcoming is mainly due to inadequate experimental results on multi-panel CLT shearwalls to help validate the developed equations and substantiate the proposed kinematic modes and shearwall behaviour. This study investigates the lateral behaviour of CLT shearwalls by carrying out two full-scale testing on shearwalls consisting of three panels and subjected to monotonic lateral load. The experimental results were used to validate results obtained from proposed analytical expressions and numerical models. Connection-level monotonic tests were also carried out on hold-down and panel-to-panel joints to be used as the input for the analytical expressions and numerical models. Preliminary results from two shearwalls tests are presented in this paper, and comparisons to the numerical models show a reasonable match.

Mohammad Masroor, Ghasan Doudak, Daniele Casagrande

Structural Specialty: Steel Structures

Parametric Study of Slender Shear Walls Reinforced with Shape Memory Alloy Bars

In mid-rise and high-rise buildings, reinforced concrete (RC) shear walls are frequently used to resist seismic forces in earthquake-prone countries. The post-earthquake repair and retrofitting of these walls are very expensive or uneconomical, as observed in the 2010 Chile and 2011 Christchurch earthquakes. This paper explores the use of shape memory alloy (SMA) bars in the plastic hinge region of slender reinforced concrete (RC) shear walls. A comprehensive numerical parametric study was performed to understand the effects of various parameters on the hysteretic (force–deformation) response. Several models were developed with different aspect ratios, axial load ratios, reinforcement ratios, and types of SMA. The walls were then subjected to axial and reverse cyclic lateral loading, and the responses were assessed. Based on the responses, new trends were identified between design parameters and response outputs such as stiffness, residual deformation, force–deformation, and critical damage states (i.e. cracking, yielding, and crushing of SMA RC walls). These new relationships can be used to inform the design of low damage SMA RC walls for high seismic regions in Canada and worldwide.

Deepak Saud, Lisa Tobber, M. Shahria Alam
Effect of Low-Cycle Fatigue on the Seismic Vulnerability of Aluminium and Steel Domes

The low-cycle fatigue resistance of a material can influence the seismic vulnerability of a structure. Aluminium alloys are generally more susceptible to failure under low-cycle fatigue compared to steel. However, aluminium is an effective solution for domes exposed to aggressive environments such as chemical storage facilities, domes covering large spaces such as stadiums and domes with structural members connected efficiently (e.g. Mero) using extruded aluminium profiles. This is due to the durability, the high strength-to-weight ratio and the extrudability of aluminium alloys. The vulnerability of aluminium domes under earthquake ground motions may be influenced by its cyclic mechanical properties, including low-cycle fatigue. The rupture of a member under low-cycle fatigue can be captured by considering the earthquake-induced plastic strain cycle in the member. In the present study, the seismic vulnerability of aluminium and steel domes under the same gravity load are compared by developing fragility functions based on incremental dynamic analyses. The results showed that the low-cycle fatigue resistance of the material has a significant influence on the seismic performance of the domes. The aluminium dome and the steel dome were able to sustain seismic loads with spectral accelerations at the fundamental period up to 2 g and 2.5 g, respectively. It was observed that the aluminium dome showed a good seismic resistance for practical intensities representative of the design spectrum of Vancouver, BC, Canada.

Akossiwa Constance Efio-Akolly, Charles-Darwin Annan
Detection of Local Buckling in Thin-Walled Hollow Structural Steel Sections Using Fibre Optic Cables

Fibre optic cable-based techniques have recently been introduced in the steel construction industry. This is due to their high sensitivity, ability to resist electromagnetic interference, be lightweight and efficiently multiplex. However, fibre optic cable sensors are still limited due to their initial high cost and unfamiliarity to the users. This paper compares fibre optic cable sensors to traditional strain gauge sensors via an experimental program comprising four-point bending and three-point bending tests. The sensors were used to detect the location and initiation of local buckling in thin-walled polygonal hollow section (PHS) and rectangular hollow section (RHS) beams. The results showed that for these deep thin-walled beams with similar cross-sectional dimensions, the PHS beams were able to reach their yield moment capacities, while the RHS beams failed due to local buckling at about 40% below their yield moment capacities. In addition, unlike the strain gauges, the fibre optic cable sensors were able to detect the location and initiation of local buckling along the length of the tested beams.

John Kabanda, Andre Brault, Colin MacDougall

Structural Specialty: Concrete Structures

Image-Based Microstructural Finite Element Model of Concrete Subjected to Freeze–Thaw Cycles

Sample-specific image-based three-dimensional (3D) microstructural finite element (FE) models of the freeze–thaw damage of cylindrical concrete samples were developed. Each model consists of image-based aggregates, cement mortar, and air voids that were constructed using high-resolution micro-computed tomography (µCT) images. The voids were later filled with water that was subjected to freezing temperatures. The applied material properties and contact conditions were adopted from the literature, and the two modeled concrete elements were subjected to 40 freeze–thaw cycles under temperatures of 0 and − 22 °C. The frost-induced stress distribution, volume loss, and damage propagation were analyzed to investigate the severity and mechanisms of the freeze–thaw damage. The volume loss and damage progression were compared well with the experimental results.

Mustafa Alhusain, Adil Al-Mayah
Finite Element Modeling of Fiber-Reinforced Polymer Composite Tubes Filled with Concrete

Sustainable development of Civil Engineering infrastructure has already benefited from the use of fiber-reinforced polymer (FRP) composite materials for different structural applications such as reinforcing existing structures and constructing new ones. Among the various FRP structural elements, ± 55° filament wound glass FRP (GFRP) tubes, which are typically prefabricated for piping application, have been considered in a number of structural applications. As a load-bearing structural element, filling these tubes with concrete (concrete-filled FRP tubes or CFFTs) can considerably enhance their stiffness and strength under axial and flexural loadings. Although there have been multiple studies on the bending and compressive behavior of CFFTs, studies on the tensile behavior of CFFTs and especially those made of ± 55° GFRP tubes are quite scarce. Here in this study, in order to take a step toward a better understanding of the behavior of the CFFTs under axial tension, finite element models of the hollow tubes and CFFTs were generated using the ABAQUS software package and verified against the experimental outputs of previous studies. Shell elements were used to model the tube while solid elements formed the concrete. The concrete damaged plasticity (CDP) model was used to introduce the material properties of the concrete to the model. Quasi-static analysis using Dynamic/Explicit solver was implemented due to its capabilities for converging highly nonlinear problems. Good compatibility of the results of the numerical study with the test outputs was seen on both hollow tubes and CFFTs. It can be concluded that the damage criteria used for FRP were capable of predicting matrix cracking as the governing mode of failure in FRP observed in the experiments. Moreover, the CDP model could simulate the tensile cracking of concrete.

Alireza Sadat Hosseini, Pedram Sadeghian
The Interfacial Bond Stresses in Concrete Filled FRP Tubes

Composite structures have gained more attention these days due to their advantages, such as high strength (because of complementary performance of core concrete and FRP tube), excellent durability, light weight, and fast erection. One of the composite structures is concrete filled fiber-reinforced polymer (FRP) tubes (CFFTs). The technology has been investigated in the past, but more attention should be paid to some specific problems, such as quantifying an adequate bond between the tube and the concrete core to act as a full-composite structure, which is an important issue, especially in flexural member. This study proposes a new and simple analytical method calculating the bond stress in flexural members. The equilibrium between the tension and the compression forces is used to develop a MATLAB code to calculate the bond stress. The section is divided into some fibers. The force in each fiber is calculated according to the stress distribution. The total tension and compression forces are calculated by the sum of fibers’ forces. The bond stress is the total tension or compression force divided by the interface between the concrete core and the FRP tube. However, the ultimate moment capacities given from tests are used in the simplified method to calculate the bond stress. The tension and the compression forces are calculated based on the arm between them. Finally, the bond stress is determined. Furthermore, a comparison between the bond stress calculated according to two methods and the bond strength data derived from push-off tests is made. The results show that although the bond stresses are a bit more than the bond strength at the ultimate condition, there is an adequate bond between the concrete and the FRP tube before reaching the ultimate condition as the differences are not too much.

Ali Alinejad, Pedram Sadeghian, Amir Fam
Development and Assessment of a Mechanical Strengthening System for Post-tensioned Concrete Bridge Cantilever Wings Using Post-tensioned CFRP Rods

This paper presents the development and experimental assessment of a mechanical strengthening system using post-tensioned (PT) carbon fiber reinforced polymer (CFRP) rods for the rehabilitation of post-tensioned concrete bridge cantilever wings. CFRP rods were selected as a direct parallel to PT steel bars owing to CFRP’s superior fatigue, corrosion resistance, and lightweight properties as a composite material. The mechanical strengthening system is a metal anchor comprised of a stainless steel barrel and split aluminum wedges in direct contact with a CFRP rod. The system strictly relies on friction for load-bearing capacity with no adhesives required. The developed CFRP mechanical anchorage system is assessed experimentally as part of a broader experimental program seeking to adequately transfer the CFRP post-tensioning force through bearing at anchorage ends to strengthen PT concrete bridge cantilever wing specimens that exhibit deterioration. The CFRP rods for strengthening will be embedded in near-surface-mounted (NSM) grooves in the negative moment region of the experimental PT concrete bridge cantilever wing specimens. The anchor features a contoured longitudinal profile consisting of a 1650 mm circular radius to minimize the stress concentrators at the loading end of the anchor, pushing the stress toward the back of the anchor. The anchor also features a competitive 80 mm in length stainless steel barrel and 80 mm in length aluminum wedge core. Seven specimens in total were carried out for the experimental assessment of the anchorage system. All prepared specimens measured 1.8 m in total length with a 1.5 m CFRP rod free gauge length in-between the ends of the anchors. Two specimens as proof of concept anchorage testing were carried out with no pre-setting load to observe the behavior of the design concept during loose wedge conditions. Subsequently, anchorage static testing was carried out with five prepared specimens. Two distinct pre-setting loads were selected to induce initial contact pressure between the wedges and the CFRP rod to reduce slippage. Three specimens were pre-set at 80 kN and two specimens were pre-set at 100 kN before tensioning. The average ultimate capacity of the anchorage system was 97.6 kN, yielding a system efficacy of 63.4% against a guaranteed CFRP tensile strength of 154 kN. Adhering to the Canadian Highway Bridge Design Code, S6-19, the CFRP rods will be post-tensioned up to an effective jacking force of 50 kN at transfer due to the anchorage effect on the CFRP rod.

Faraj Shahrstan, Pedram Sadeghian
Ultimate Drift Capacity of Flexure-Dominant Reinforced Concrete Masonry Shear Wall

Reinforced masonry (RM) has been practised in Canada for more than 50 years, mostly for construction of low- to mid-rise buildings. The National Building Code of Canada 2015 [NBCC (2015) National building code of Canada 20 National Research Council, Ottawa, ON, Canada] permits the use of ductile shear wall class for tall masonry buildings with the height limit of 60 m at sites with moderate seismic hazard and 40 m for high seismic hazard sites, but the application of ductile shear wall in tall (more than 40 m high) RM buildings is still very limited in Canada. There is a very limited research evidence related to seismic response of these structures. One of the most important properties for seismic design of ductile RM shear walls is the ultimate drift capacity, which varies significantly depending on failure mechanism(s). This paper reviews past experimental research studies on the subject and presents a database of 66 flexure-dominant RM shear walls. A statistical analysis of the data contained in the database has been performed to determine the governing parameters which are expected to influence the ultimate drift capacity of flexure-dominant RM shear walls. Moreover, this paper also proposes an approach for predicting ultimate drift capacity of RM shear walls, based on the governing parameters determined through experimental studies.

Yu-Cheng Hsu, Miaoyuan Dou, T. Y. Yang, Svetlana Brzev
Stress–Strain Behaviour of Boundary Elements in Reinforced Block Masonry Shear Walls Under Uniaxial Compression

Reinforced masonry shear walls (RMSWs) constructed using hollow concrete blocks are commonly used in medium-rise and high-rise reinforced masonry buildings. Past research has shown that RMSWs can be used as an effective seismic force resisting system (SFRS) as they can dissipate stable energy through ductile inelastic deformations. The seismic performance of RMSWs can be enhanced by special boundary elements, which are either barbell sections connected to the wall or integrated within the wall ends. The knowledge of stress–strain behaviour of boundary elements subjected to uniaxial compression is needed to accurately estimate the inelastic behaviour of RMSWs. This paper presents a detailed review of previous studies on boundary elements in RMSWs. The paper also presents an ongoing experimental programme performed by the authors, which includes testing of 4-course grouted reinforced block masonry prism specimens. The purpose of the testing programme is to study the effect of confinement on uniaxial strength and deformations in boundary elements. The influence of various parameters, including tie spacing, hook details, and grout strength on compressive strength and ultimate compressive strain of the prism specimens is investigated in the study.

Miaoyuan Dou, Yu-Cheng Hsu, Svetlana Brzev, T. Y. Yang
Experimental Testing of Partially Grouted Masonry Shear Walls with Different Horizontal Reinforcement Types

Partially grouted (PG) masonry shear walls are widely used as lateral force-resisting systems in North America due to their economic value and practicality. Unlike fully grouted (FG) shear walls, only cells containing reinforcing steel are grouted in PG walls leaving the remaining cells hollow. With the wall assemblage consisting of materials such as masonry block, mortar, grout, and reinforcing steel, the overall behaviour is complex. To understand better the in-plane response of PG walls, experimental testing has been used as a viable tool. However, few experimental studies have been carried out to investigate PG walls compared with FG walls. Moreover, if available, some studies lacked full-scale test specimen size, compliance to the actual masonry construction, and well-documented reports. As a result, North American code equations have been obtained based on FG walls data leading to uneconomical designs while being unconservative in some cases. This paper describes the preliminary experimental results of four full-scale partially grouted masonry shear walls. These walls were designed and built to reflect the conventional construction practice, including wall geometry, reinforcement distribution, boundary conditions, and loading scenario. All the walls were subjected to constant vertical load, and reverse in-plane lateral cyclic load incrementally increased. The variable design parameters investigated in this study were: aspect ratio and horizontal reinforcement type (bond beams or bed-Joint reinforcement). These walls’ response was evaluated in terms of damage progression, in-plane hysteresis curves of lateral load against drift ratio, and energy dissipation. The experimental results revealed that lateral load capacity attained by walls with similar aspect ratios had no significant difference regardless of the reinforcement type. On the other hand, the aspect ratio had a significant effect. Moreover, the effect of bed-joint reinforcement was more visible in controlling the damage progression by distributing new cracks throughout the wall panel instead of widening the existing cracks.

Amr Ba Rahim, Carlos ‘Lobo’ Cruz Noguez, Clayton Pettit

Structural Specialty: Innovation in Structural Engineering

A New Methodology to Predict Cumulative Plastic Ductility Capacity of Steel Buckling-Restrained Braces

This paper presents a database of buckling-restrained brace (BRB) cyclic tests and predicts the cumulative plastic ductility (CPD) capacity of BRBs by using a regression-based machine learning (ML) model trained using the collected data. A summary of the past cyclic tests performed on BRBs is first presented. The hysteretic responses obtained from the test data along with influential, constitutional, and geometrical properties of tested BRBs are leveraged to develop the predictive model for the CPD capacity. The CPD capacity of prototype BRBs predicted using the predictive model proposed here agrees well with the test data, confirming the accuracy and efficiency of the ML-based technique employed here. Such a predictive model can be used in practice to size BRB cores in the preliminary design stage.

Ali Sadrara, Siamak Epackachi, Ali Imanpour
Reliability Based Optimal Design of Magnetic Negative Stiffness Damper Based Inerter for Efficient Energy Harvesting

This study proposes a magnetic negative stiffness damper-based inerter (MNSDI) for mitigating wind-induced vibration of tall structures and energy harvesting. The proposed control system has a nonlinear magnetic negative stiffness damper which does not add any additional stiffness into the combined system by which the adjoining members of the proposed control system do not experience any additional force demand. Due to the movement of the magnets inside a conductive pipe, MNSDI introduces eddy current damping into the structural system. An electromagnetic transducer is attached to MNSDI to convert vibrational energy to electrical energy. As the proposed system is a passive damper, the design parameters related to the damper are needed to estimate before installation. In this context, a reliability-based design optimization (RBDO) is used to estimate the design parameters of MNSDI, so that maximum energy harvesting can be achieved. As the RBDO framework is computationally expensive, Kriging is used as a surrogate model. For the numerical demonstration, a 76-storys high-rise benchmark building is considered. The stationary wind loads are used where fluctuating components of wind loads are simulated from the Davenport spectrum. The numerical results show the effectiveness of the proposed control system to reduce the structural vibration as well as enhance its energy harvesting capability simultaneously.

Sourav Das, Solomon Tesfamariam
Computational Wind Load Evaluation and Aerodynamic Mitigation of Low-Rise Building with Complex Roof Geometry

Climate change is the leading cause of the increasing intensity and occurrence frequency of wind events, inducing significant environmental, and economic consequences on communities and cities. A significant wind-induced load is initiated during a windstorm, mainly impacting the roof, leading to extensive roof damages or even roof total failure. Typical roof shapes (i.e., gable/hip) are generally designed using provision codes and standards. The wind tunnel test is required when designing complex roofs of low-rise buildings, as it experiences complex loading patterns attributed to the various possible roofing shapes and turbulent characteristics within the atmospheric boundary layer. This roof can be efficiently improved using computational modeling, including high-fidelity large eddy simulation (LES) to provide quantitative assessment for wind load in the primary stage of the design process to narrow down the design alternatives. The current study targets an isolated complex roof shape and utilizes LES and consistent discrete random flow generator (CDRFG) technique to simulate a model size of 1:50 to assess numerically wind load prediction by validating it with wind tunnel results. The current study aims to numerically (i) evaluate wind load on an isolated low-rise building with complex roof geometry for various angles of attack and (ii) mitigate the roof aerodynamically using parapets added corners to reduce the wind impact on the roof. The validation shows that both the mean and RMS pressure coefficients agree with the wind tunnel. The latter is evident for the effectiveness of that numerical evaluations as a precautionary method for the preliminary stage of the design of buildings. It was found that roof surfaces with solid parapets added to the corners can effectively reduce wind uplift forces on average by 15%.

Raghdah Al-Chalabi, Muhammad Ibrahim, Ahmed Elshaer

Structural Specialty: Seismic and Structural Analysis

Parametric Study of a Cable Dome of Geiger-Type

Cable and membrane structures are typically geometrically flexible and are subject to larger deflections under loads when compared to geometrically rigid structures. As one of the well-known types of cable roofs, the preliminary design of cable domes requires assigning appropriate prestress to the cables and struts taking into account the strength, stability, and serviceability requirements under different load conditions according to design codes. The ideal prestress is assigned initially based on the geometrical arrangements of cables and struts then magnified according to the load carrying capacity of the dome. The arrangement of cables and struts can affect the ideal prestress and, eventually, the total weight and maximum displacement of the dome under service loads. In this regard, this study performs a parametric study to investigate the sensitivity of some geometrical parameters (radial divisions and number of sectors) to the maximum displacement and total weight of a cable dome of Geiger-type. A code was developed to determine the initial prestress of 12 domes (with configurations of 2 hoops and 10 sectors up to 4 hoops and 20 sectors) using singular value decomposition technique. Then, 12 domes were modeled using SAP2000 and subjected to service loads according to the NBCC code. The results of this study showed that the total weight and maximum displacement remain relatively constant when increasing the number of sectors. On the other hand, increasing the number of hoops leads to significantly less displacement and a heavier dome. Based on these results, it can be concluded that domes with a larger number of hoops perform better under external loading but resultantly are heavier and therefore more expensive.

Hannah Tulloch, Elshaimaa Ahmed, Ashraf El Damatty
Seismic Fragility of Using Friction Dampers to Retrofit Non-ductile Reinforced Concrete Shear Wall Buildings in Western Canada

Reinforced concrete (RC) shear wall buildings designed pre-1980 in Canada are vulnerable to earthquake hazards due to insufficient ductility and brittle failure mechanism of the shear wall. Energy dissipation devices, such as friction dampers, bear the potential to enhance the earthquake resistance of civil engineering structures, while their applicability to shear wall buildings remains unclear. One fundamental challenge lies in the lack of a viable layout design of damper devices to fully engage their stroke capacity to dissipate sufficient earthquake energy. This challenge is aggravated in western Canada because of its elevated level of seismicity. To address these issues, this study relies on seismic fragility analyses to explore the effectiveness of using friction dampers to retrofit non-ductile RC shear wall buildings in western Canada. Finite element models are developed to integrate nonlinear behaviours of shear wall buildings, different layout designs of friction dampers, and their hysteretic force–displacement relationships. Site-consistent seismic hazard model is developed for a benchmark site in western Canada, namely the city of Victoria, from which a large suite of spectra-consistent ground motions is selected for nonlinear time history analyses. By comparing seismic demand with the shear wall’s capacity, different sets of seismic fragility models are developed to assess to what degree each proposed damper design would change the seismic fragility of shear wall building.

Chunxiao Ning, Yazhou Xie
Seismic Response of Single-Layer Lattice Domes Made from Steel and Aluminium

Lattice domes are used in the construction of stadiums and airports to accommodate many people. These structures fit into the high seismic importance category because they serve as shelters in case of seismic events. Information based on research regarding the seismic design of domes exists; however, the practical application of this information by the designer remains a daunting challenge. Essentially, there are no established guidelines for the seismic design of domes. Given that aluminium is fast evolving as an effective alternative to steel in the construction of domes, the objective of this study is to assess the seismic performance of an aluminium dome in comparison with a steel dome using modal analyses, modal pushover analyses and nonlinear time history analyses. The selected ground motion for the time history analyses is the 1995 Kobe earthquake with a peak ground acceleration of 0.48 g. It was observed that the modal characteristics of both domes were similar. There was no permanent deformation in both domes under the unscaled ground motion. However, at higher seismic intensities, permanent deformations occurred, and both domes had about the same residual displacement. For all levels of seismic intensities considered, the aluminium dome experienced more displacements than the steel dome.

Akossiwa Constance Efio-Akolly, Charles-Darwin Annan
Multi-Dimensional Seismic Vulnerability Assessment of CLT Coupled Wall System

In this paper, multi-dimensional seismic vulnerability assessment is performed for a cross-laminated timber (CLT) coupled wall (CLT-CW) system. The CLT-CW structural system uses multiple balloon type CLT shear walls connected, at every story, with replaceable coupling beams. For the seismicity of Vancouver, British Columbia–Canada, five 10-story CLT-CW buildings with coupling ratio (CR) values 10–50%, are examined. Two-dimensional numerical model of the system is developed in OpenSees, and incremental dynamic analysis (IDA) is performed using 30 (bi-directional) ground motion records. Bi-dimensional damage demands, maximum inter-storey drift ratio, and residual drift ratio are used to compute the corresponding fragility curves at three different limit state capacities, namely immediate occupancy (IO), life safety (LS), and collapse prevention (CP). From the analyses, it is shown that CLT-CW systems with higher CR values are less vulnerable when compared with those of lower CR values. Moreover, this study has investigated the effect of different combinations of the limit state functions on the resulting fragility curves and seismic vulnerability of the systems.

Biniam Tekle Teweldebrhan, Solomon Tesfamariam
Structural Layout Optimization of Tall Buildings Against Wind Load

Nowadays, tall buildings are playing an important role in fulfilling the increasing demand for housing in urban cities. The design process of tall buildings is quite complex, and it requires continuous collaboration between different engineering fields and architects to satisfy the target functionality at a suitable cost. Since tall buildings are sensitive to lateral loads, a change in their layout, size, or shape will affect their cost and behaviour. In this paper, a case study for topology optimization is presented to find the optimal lateral resisting system layout against dynamic wind load for tall buildings, by altering the configuration of shear wall segments. First, an automated finite element (FE) model is adopted to assess the structural performance against static wind loads provided by the National Building Code of Canada. These models are integrated with a genetic algorithm, in order to identify the optimal configuration of the structural system. A comparison is held between dynamic time history wind loads and equivalent static wind loads to investigate the effect of including dynamic loads within the optimization framework. This study demonstrates the potential capability of topology optimization in tall buildings, which can increase the wind performance of the tall building, while reducing the overall cost of the structure within predefined architectural and structural constraints.

Magdy Alanani, Ahmed Elshaer
Structural Fatigue Crack Localization Based on EMD and Sample Entropy

During structural vibration, fatigue cracks, especially at their initial stage, introduce a repetitive crack open-close breathing-like phenomenon. Breathing cracks cause irregularities, bi-linearity, or perturbations in the vibration response of a structural system. Entropy can be used to quantify the irregularity or bi-linearity in those responses, and the crack position can be determined since on the two sides of the breathing crack, there is an apparent variation of entropy values. Here, we present a new breathing crack localization method based on a spatially distributed entropy approach coupled with the empirical mode decomposition (EMD). EMD is used as a pre-processing tool to extract the characteristics caused by breathing phenomenon in the vibration signal, and the reconstructed signal is used for entropy calculation. The location of the crack can be estimated by entropy values at different positions of the test structure. To verify the accuracy of the proposed method in localizing the breathing crack, the results were compared with a series of laboratory experiments in a beam. It is concluded that the proposed approach can be effectively used for breathing crack localization in a structural system.

Shihao Cui, Pooneh Maghoul, Nan Wu
A Time-Dependent Probabilistic Approach for Safety Assessment of Brittle Elements in Bridge Structures

As bridge structures age, their metallic members deteriorate due to corrosion and cyclic stress. Over time, this deterioration can lead to failure of various bridge members, either due to yielding, buckling, or brittle fracture, which can potentially cause the collapse of the bridge structure. For this reason, routine assessment and maintenance procedures, including finding, monitoring, and retrofitting defects in early stages, are essential to the safety of bridge structures. However, there are elements in bridge structures that are either hardly accessible or inaccessible, rendering visual inspection hard or impossible. Pins in pinned connections of truss bridges are examples of such members. This situation can be even more problematic when brittle fracture, which can occur with little warning, is a potential failure mode. In the case where inspections cannot be efficiently conducted, numerical approaches such as probabilistic fracture mechanics methods can be effectively employed to assess the safety of such bridge elements and provide useful information on such things as the critical defect size. This information can be useful for assessing the suitability of more drastic non-destructive evaluation (NDE) measures or making decisions regarding retrofitting. In this regard, a probabilistic approach based on the Eurocode EN1993-1-10 fracture mechanics method is used in this paper to assess the probability of failure of a typical pin used in large steel truss bridges. With this information, this paper presents a comprehensive methodology for assessing critical crack sizes for the pins of the bridge example, which considers the probability of brittle fracture.

Mohammad J. Tolou Kian, Michelle Y. X. Chien, Scott Walbridge

Structural Specialty: Durability of Structures

Condition-Based Maintenance of Highway Bridges Using Q-learning and Considering Component Dependency

A bridge comprises many structural components, most of which are critical to its safety and must be maintained periodically. Finding the optimal maintenance policy for a bridge is challenging as each component has a unique deterioration process, and component failures interdepend. Moreover, the components have specific repair schemes with different effects. Maintenance work may involve various combinations of these repair schemes. In this study, we develop a bridge management approach that recommends repair schemes based on routine inspection results. The proposed method uses Q-learning to determine optimal maintenance decisions. The objective is to minimize the total maintenance and user costs in a given planning horizon. Deterioration models for the structural components are obtained using routine inspection data. Q-learning intelligently discovers available repair schemes while repeatedly simulating possible trajectories of bridge states throughout the planning horizon, and eventually summarizes the optimal repair schemes for a given bridge state. This approach eliminates the need for elaborate modeling of structural degradations and repair effects. The proposed decision-making framework is illustrated using an example steel girder bridge.

Gaowei Xu, Fae Azhari
Long-Term Durability of Shear Critical GFRP RC Beams

An extensive experimental and analytical research programme underway at the University of Toronto includes 12 GFRP-reinforced beams (10 flexural critical and 2 shear critical) with 3000 mm span length. Due to the space limitation, only the detailed results of shear critical beams are discussed in this paper. Both the beams were completely reinforced with GFRP straight and bent bars. One beam was tested at room temperature and the second beam was subjected to accelerated thermal conditioning to simulate long-term behaviour of GFRP RC beams considering the recent climate challenges leading to increasing temperatures across the world. Conditioning of the beam was carried out at 50 °C for four months under 60% relative humidity while subjected to sustained load throughout the conditioning period. No significant reduction in the capacity was observed because of the conditioning.

Jahanzaib, Shamim A. Sheikh
Simplified Analysis of RC Beams Exposed to Fire

With performance-based design becoming more prevalent in today’s standards, practical and simplified methods are needed to model and analyze reinforced concrete (RC) structures. These methods must meet the time and cost constraints for the practitioners, while maintaining a high degree of accuracy. Fire incidents are initiated by the ignition of combustible materials and can spread vertically and horizontally based on the specific compartment boundary conditions. RC elements, which are exposed to fire, develop a time-dependent three-dimensional temperature gradient. The developed temperatures cause the element’s stiffness to degrade and result in thermal induced deformations. This research introduces two simplified numerical methods to analyze continuous RC beams during fire exposure. The first method divides the beam into predefined segments and uses iterations to define the stiffness for each segment. An automated program was developed to conduct the iterations and redistribute the moments until convergence is achieved. The second approach assigns nonlinear plastic hinges to the predefined segments. The moment–curvature diagrams for these hinges account for the effect of fire exposure. Predictions of both methods were validated using published research by others.

Lochlan R. Medeiros, M. A. Youssef, S. F. El-Fitiany

Structural Specialty: Analysis and Design of Bridges

Seismic Retrofitting Strategies and Engineering Solutions of Kanaka Creek Bridge on Highway 7

Kanaka Creek Bridge carries Highway 7 over Kanaka Creek in Maple Ridge, British Columbia. This paper presents the seismic evaluation and retrofit design adopted for the Kanaka Creek Bridge. Response spectrum analysis was performed under three seismic hazard levels to evaluate seismic performance of the bridge structure. Capacity over demand ratios were employed as main indicators for seismic assessment of critical bridge structural components and connection elements in the seismic load path. Pushover analysis was performed at the abutments to understand the structural performance of the steel pipe piles after yielding. Given the potential of abutment soil liquefaction during seismic events, soil lateral spreading effects and vertical downdrag effects on steel pipe piles were evaluated. After identifying the potential structural failure mechanism, the designers proposed performance-based seismic retrofitting solutions with additional drilled-in steel dowel at bridge abutments and link slabs at bridge deck over piers. This seismic retrofitting scheme provides deck continuity, improves the longitudinal load path and strengthens the connections between superstructure and substructure. The project was completed on time and within the approved budget.

Lihua Zou, Kai Li, Yuming Ding, Samson Chan
Time-Dependent Probabilistic Analysis of Steel Bridge Brittle Fracture

Brittle fracture is a major concern to structural engineers as it has significant consequences in terms of safety and cost. Although modern day occurrences are rare, it is well known that they can occur without warning and may lead to the sudden closure of a bridge, loss of service, expensive repairs, and/or loss of property or life. In Canada, steel bridge fracture is a more significant concern due to the harsh climate, which, if the toughness properties are improperly specified, could put many steels on the lower shelf of the toughness-temperature curve. In the existing CSA standards, design against brittle fracture solely depends on the temperature of the location of interest, and other factors impacting fracture, such as stress level and plate thickness are currently neglected. A previous comparison of brittle fracture design provisions around the world revealed that more sophisticated approaches have been developed in terms of modelling and understanding brittle fracture than the ones currently in use in North America. One of these procedures is the fracture mechanics method in the European EN 1993-1-10 standard. This paper briefly describes this method and then shows how it can be implemented in a probabilistic framework, using historical temperature and truck data to determine the failure probability with respect to temperature and traffic loadings fluctuating on a time scale throughout the year.

Michelle Y. X. Chien, Mohammad Javad Tolou Kian, Scott Walbridge
Unified Seismic Capacity Limit State Models of Reinforced Concrete Bridge Columns

Highway bridges are crucial links in the transportation network. Their seismic damage and failure have caused casualties, economic losses, and long-term impacts to the affected regions. To date, extensive studies have made efforts to understand the seismic behavior of bridge column, given its vulnerability in affecting seismic fragility/risk assessment of existing bridges and performance-based seismic design (PBSD) of new bridges. In both regards, seismic capacity models constitute an essential element indicating various limit state criteria under increasing levels of earthquake loading. The capacity models of reinforced concrete (RC) columns describe discrete observable material behaviors as damage states, which are further quantified into numerical limit states through various engineering demand parameters (EDPs), including drift ratio, displacement ductility, curvature ductility, and local strains of longitudinal steel, and unconfined and confined concrete. Despite abundant publications, research findings by using various types of EDPs are often scattered and sometimes conflicting, thereby preventing a direct comparison toward a unified column capacity model. Also, different limit state models have been found when the same EDP is used. Such inconsistency motivates the current study to develop a unified column capacity model, where the benchmark case is considered for the modern-designed circular RC columns with ductile seismic behaviors. In doing so, a comprehensive literature review is carried out to synthesize different RC column capacity models used by both researchers and practitioners. Furthermore, cyclic pushover analyses are conducted to convert these models into those used by a shared EDP type—the maximum local strains of concrete and steel. As such, a unified set of capacity models will be developed by incorporating all sources of variations embedded in the literature. The developed model will be the first-of-its-kind and will lay a solid foundation for stakeholders to conduct more reliable seismic fragility/risk assessment of existing bridges and PBSD of new bridges.

Yihan Shao, Yazhou Xie
Development of Canadian Design Standards for Traffic Barriers for Bridge Applications

This paper summarizes the research work done in Canada on steel- and GFRP-reinforced concrete barriers. AASHTO LRFD Bridge Design Specifications specify a triangular yield line failure pattern for steel-reinforced concrete barrier design. However, no evidence was found in the literature to support this failure shape. Recent experimental tests on steel-reinforced barriers showed a trapezoidal crack pattern within the barrier that led to the development of new equations for the barrier transverse flexural capacity using the yield line theory. These equations along with conditions for their use were included in the 2019 Canadian Highway Bridge Design Code (CSA-S6.19). Also, a new punching shear equation for the barrier transverse capacity was developed based on the experimental findings. Due to the use of de-icing salt in winter times, GFRP bars have been used in Canada as a cost-effective alternative to corroded steel reinforcement. Recent design work on a GFRP-reinforced barrier was qualified by conducting three vehicle crash tests using different types of GFRP bars. Then, static load tests to collapse were conducted on the constructed barriers to study their structural behaviour. Test results showed that their failure mode was punching shear at the transverse load location, with trapezoidal-shape flexural cracks appearing at the tapered faces of the barrier during loading. Experimental findings were incorporated in CSA-S6.19 in the form of GFRP bar size, and arrangement to satisfy the crash test acceptance criteria and equation for the punching shear capacity of GFRP-reinforced barrier subjected due to transverse vehicle impact loading.

Khaled Sennah

Structural Specialty: Ground Structures

Estimation of Permanent Ground Displacement Capacities for Corroded Pipelines

Permanent ground displacements (PGD) occur either due to earthquake-induced ground failures, such as lateral spreading, or due to landslides, and in turn, could induce significant strains in buried pipelines. When the induced strains exceed the strain capacity, buried pipelines could suffer potential rupture or compression/buckling failures as evidenced from past earthquake events. Research efforts, including rigorous experimentation and numerical analyses, have led to procedures for evaluating and quantifying pipe stress/strain capacities to withstand PGDs of intact pipelines subjected to ground movements. When pipelines that have experienced corrosion are encountered, their PGD capacities would be certainly different from those of intact pipelines. In pipeline risk assessments, there is a need to account for the corrosion effects on the PGD capacity—in particular, this requires having relatively simpler ways to without resorting to rigorous analyses to address this multi-hazard problem. With this impetus, in the present study, different available approaches were explored to obtain the PGD capacities of corroded pipelines. As the response is dependent on the orientation of pipelines with respect to the ground movements, the PGD capacities were determined considering several cases of straight steel pipe sections subjected to PGDs in both longitudinal and transverse direction to the pipe alignment. Assuming that corrosion effects could be represented by an equivalent pipe wall thickness (i.e., uniform reduction in pipe wall thickness due to corrosion), modification factors were developed to adjust the PGD capacities of intact pipelines to account for different degrees of corrosion.

Prajakta Jadhav, Dharma Wijewickreme
Analyzing Geosystems with Deployable Compliant Mechanisms for Enhanced Tension Capacity

Current research into deployable and compliant structures focuses on their applications above-ground. Deployable structures have benefits in the construction industry because they can be transported compactly and installed easily on site. These benefits can be extended to underground applications which have not been widely investigated experimentally. Geotechnical structures, loaded primarily in tension, risk brittle collapse or displacement accumulation under extreme loading. To address this concern, members are oversized or components are added. Deployable structures offer a way to resist extreme design loading while increasing system resiliency and decreasing material cost, transport, construction time, and environmental impact. The goal of this work is to develop compliant attachments to the exterior of tension-loaded geostructures that deploy passively and increase the bearing area and capacity. This novel arrangement consists of a tension-loaded member (a pile) and compliant components (awns). When twisted, the awns deploy, entrapping soil and increasing surface friction. This increases the tensile capacity of the pile. Test members are fabricated via additive manufacturing using rigid polymer and rubber from Stratasys. They are rotated in clear sand by manually pulling cables with a load cell to measure applied tension. Using a machine vision plugin, rotation data is collected from video footage during experimental tests. The performance of the geometry is evaluated based on predictable awn deployability and the tension load of the geosystem. This paper presents parametric studies and experimental tests of adaptive torque-driven underground structures at small scale. With both structural and sustainability benefits, the deployable attachments increase the tension capacity of ground anchors while decreasing the embodied energy of the anchors.

Kaylee A. Tucker, Ann C. Sychterz

Structural Specialty: Modular Structures

Prefabrication and Modular Construction—A Potential Solution to Affordable and Temporary Housing in Ontario?

Canada’s housing crisis, and particularly Ontario’s, has reached an all-time high in recent years. Due to the lack of affordable housing, the federal government created the Rapid Housing Initiative (RHI) to fund the construction of affordable housing units. The RHI has a twelve-month delivery date from funding requirement which has contributed to partners turning to the use of prefabrication and modular construction methods to produce housing units in large quantities and in a timely manner. The current study investigates successful modular projects in Ontario in order to identify their key success-driving factors as well as limitations. These success drivers included the structure durability, ability to deploy and relocate, ability to flat-pack the structure for transportation, and the primary funding source for the project. Based on these factors, it is concluded that there is a gap in the industry in panelized relocatable housing structures. Whereas prefabrication and modular construction have been successful thus far in major cities, the study highlighted the need for a prefabricated or modular sustainable assembly using either light-frame wood or mass timber that can be easily deployed, assembled, and transported to meet the housing demand in remote communities in Ontario.

Daniela Roscetti, Andrea Atkins, Daniel Lacroix
Low-Rise Modular Structure Wind Load Evaluation

Low-rise buildings represent the majority of commercial, residential, and industrial buildings. This raises the importance of accurately assessing the wind loads developed on their surfaces. Typical low-rise buildings can be designed using wind load obtained from methods provided by design codes. As for non-typical low-rise buildings, they require more sophisticated methods of wind load evaluation. In addition, with the increasing demand for healthcare space due to COVID-19, the urge to meet the space demand calls for immediate action to overcome this issue. When it comes to construction, the conventional method may not provide a prompt solution to the urgent need for healthcare space. This highlights the importance of utilizing advanced construction methods (e.g., modular construction) to respond to such problems. Modular construction relies on the use of prefabricated units that can be assembled on-site to form different types of structures. The application studied in this paper primarily focuses on the use of modularly constructed structures to provide healthcare space. Since modular buildings are typically of irregular layout low-rise buildings, wind load distribution can be complex compared with typical structures; thus, the expected wind load on different modules within the layout may vary. Accordingly, this paper demonstrates the non-typical wind distribution developed on a modularly constructed hospital. The computational fluid dynamics (CFD) method is utilized to evaluate wind loads developed on a non-typical layout. Based on the study results, critical forces developed on surfaces were found to be different depending on the module’s location within the layout. Different corners, edges, and internal modules are examined in this study. The results of this study can be further used to design different grades of modules; thus, achieving better usability of materials.

Mutaz Suleiman, Ahmed Elshaer

Transportation Specialty: Road Safety and Traffic Operations

A Python Extension in Sumo for Simulating Traffic Incidents and Emergency Service Vehicles

Traffic signal retiming and coordination play a significant role in traffic management, especially when the traffic incidents disrupt the network. Many researchers have developed artificially intelligent (AI) traffic signal controllers based on goal-oriented machine learning frameworks to try and optimize network performance. However, previous efforts have lacked the means to evaluate these networks under traffic incident conditions. To make these AI traffic signal controllers more robust, current research needs to consider AI traffic controller performance under traffic incidents and accompanying emergency response. Obtaining field incident data and converting into inputs for simulation models to evaluate these machine learning models has been a huge hurdle because it is expensive, time-consuming, and sometimes even unfeasible. This paper provides an integrated traffic incident and response simulation tool for a grid network made in Simulation of Urban MObility (SUMO) to overcome this gap. The tool includes random traffic incident generation (location and duration), incident detection, random emergency vehicle generation, and emergency vehicle dispatching. With this tool, users can simulate a road network with traffic incidents and emergency vehicle response to produce substantial amounts of data for training robust reinforcement learning models. In addition, this tool will save future researchers and practitioners both time and effort in testing the impact of their proposed AI traffic control models and allow for a more complete evaluation of performance.

Tianxin Li, Wei Zhao, Carolina Baumanis, Jennifer Hall, Randy Machemehl
Operating-Speed Models for Horizontal Curves on Two-Lane Rural Highways: Case Study in Nigeria

Geometric elements of highways play a significant role in accident occurrences on curves. Hence, curved sites and the corresponding transition sections represent the most critical locations when considering safety measures on rural highways. Excessive speeds may cause inconsistency in a horizontal alignment. Hence, attaining geometric consistency is vital in designing and redesigning two-lane rural highways. Operating speed models were developed to evaluate operating speed consistency on a two-lane rural highway in Nigeria using speed data for 111 horizontal curves. The test of significance on the vehicle speed in the different lanes and the consistency of speed measurements show no statistical difference between the speeds in both directions. Also, at the 5% significance level, there is no statistical significance between the speed data obtained using a stopwatch and an automatic counter. However, the automatic counter allows for more observations. Based on the different categories of curve radius (CR) considered in the model development, Model 1 with CR < 1200 m has a statistically significant and influential relationship. Thus, this model is highly recommended for operating speed prediction on horizontal curves in Nigeria.

Abayomi Afolayan, Oladapo Samson Abiola, Said M. Easa, Funmilayo Modupe Alayaki, Olusegun Folorunso
Improving Safety of Rural Intersection with Approaching Reverse Curve

This paper exhibits the safety improvement study for the reverse curve and unsignalized stop-controlled intersection at Regional Road 14 and Young Street in the Niagara Region. Regional Road 14, also known as Thirty Road, is a major road running north/south in the Town of West Lincoln. Under current conditions, many collisions have been reported at the intersection of Thirty Road and Young Street and along the reverse curve portion of Thirty Road itself. With a projected annual growth rate of 5%, traffic volumes travelling in the direction of Smithville are expected to increase by 2041 drastically. This study aims to evaluate viable design alternatives and further develop the selected improvement that can safely accommodate the projected 2041 traffic volumes for Thirty Road at Young Street. Data provided by the Niagara Region for analysis includes existing geometric conditions, utility locates, 2019 collision data, 2011 baseline volumes, and forecasted volumes for the horizon year 2041. The alternatives presented are realignment of the reverse curve with a roundabout, signalized intersection, or all-way stop intersection. The evaluation criteria used in the analysis are as follows: safety, level of service, cost, and environmental impact. A ranked system in tandem with weighted criteria was used to assess the level of influence of the alternatives, with the results then weighted using the final evaluation model. The evaluation showed that the alternative with a roundabout was the best. Surrounding utilities and other constraints were considered when developing detailed designs of the improved realignment and intersection using AutoCAD Civil 3D.

Devashree Rege, Dewmi Seneviratna, Tazrian Hassan, Viththahan Puvanendran, Hamed Esmaeeli, Manny Rataul, Sulaf Alkarawi, Arkatkar Shriniwas, Said M. Easa
Redesigning an Urban Midblock Section to Improve Safety and Level of Service: Case Study in the Niagara Region

Providing safe and complete streets that fit road users of All Ages and Abilities (AAA) with optimal traffic flow along urban built-up areas can often be challenging. Increased access points along midblock sections between busy intersections result in higher travel speeds, jaywalking, and delays. This paper evaluates a case in the Niagara Region, where the main corridor, Regional Road 20 (Lundy’s Lane) between Montrose Road and Kalar Road, is being accessed for improvements. This corridor has many different factors, including multiple nursing homes, a secondary school, tourist accommodations, and local businesses. The alternative solutions included: implementing a road diet with a cyclist facility, two-way left-turn lanes, adding pedestrian crossing and numerous other minor improvements (Alternative 1); and implementing partial road expansions along the corridor to add in pedestrian refuge islands, partial channelized left-turn lanes, and additional minor improvements (Alternative 2). The best alternative was chosen through evaluation using four criteria: safety, traffic operations, cost, and environmental impacts. Each criterion was given a corresponding weight, and the best alternative was chosen through a weighted scoring method. Sensitivity analysis is also conducted for the weights and the proposed growth rate for the 2041 design year. In this regard, Alternative 1 showed the best fit with evaluation criteria. A detailed design of this alternative was created using AutoCAD, and PTV Vissim and Synchro were used to analyze the impact on traffic operations along the midblock section.

Anish Nothoo, Zian Liu, Brahmjot Grewal, Sulaf Alkarawi, Manny Rataul, Hamed Esmaeeli, Essam Dabbour, Said M. Easa
Traffic Delay Analysis in Road Rehabilitation Projects: A Simulation Approach

Population growth has put a great strain on our highway networks leading to an ever-greater need for road rehabilitation and reconstruction. Highway networks are overloaded with new commuters every day; leading to ever-increasing congestion levels. These congestion levels are exacerbated when there are construction activities, and a road cannot be rerouted. Consequently, user cost has become an essential part of the economic evaluation criteria for the decisions that go into planning road rehabilitation projects. The lost economic output due to the delay time incurred by road users forces governments to plan these projects on tight schedules and may even penalize the contractor for failing to finish on a certain date. Contractors engaged in road rehabilitation projects are continuously asked to work in expedited conditions to minimize the delay time incurred by road users. This makes the planning phase of any road rehabilitation project essential for successfully finishing the project on time. Simulation provides a capable tool for any contractor to aid in properly strategizing for road rehabilitation projects. From contractors’ point of view, they can choose a strategy that satisfies the minimum delay versus project duration trade-off. This paper aims to allow the evaluation of the delay that is suffered by the users of four-lane freeways under different scenarios. The delays for the different number of lanes closed, working off-peak hours and different lengths of reconstruction area are evaluated using Anylogic simulation software. The results of this study should help contractors decide on the type of strategy to approach road rehabilitation projects based on delay time versus project duration trade-off.

A. Sorour, A. Abdullah, Y. A. S. Essawy, K. Nassar
Performance Evaluation of Turbo and Double-Lane Roundabouts

This paper aims to compare and evaluate turbo (TB) and double-lane (DL) roundabouts. The two types of roundabouts have many similarities and some differences. Thus, engineers are facing difficulty deciding which design is more effective. This paper evaluates both roundabouts regarding safety, performance, pollution, directional split, level of service, and capacity. The TB roundabout has fewer conflict points than the DL roundabout. The results show that the TB roundabout provides more capacity when the right-turn movement from the minor entries is high. Otherwise, DL and TB roundabouts perform similarly. The TB roundabout is the best design for reducing local pollution levels. However, if the aim is to reduce CO2 and NOx specifically, the DL roundabout is better. Furthermore, there are various parameters to evaluate the effectiveness of DL and TB roundabout designs, such as stopping sight distance, intersection sight distance, and the fastest path. The approaching speed for DL and TB roundabouts is 25 mph (40 km/h) and 20 mph (32 km/h), respectively. The minimum sight distance to approach the crosswalk and stop safely for DL and TB roundabouts is 152 ft (46 m) and 112 ft (34 m), respectively, indicating that the TB roundabout is a safer design. Nonetheless, the minimum entering sight line distance is larger in TB than DL for intersection sight distance, 197.2 ft (60 m) and 151.7 ft (46 m), respectively.

Roua Alkadi, Said M. Easa

Transportation Specialty: Data, Analytics, and Technology

Station Reallocation and Rebalancing Strategy for Bike-Sharing Systems: A Case Study of Washington DC

Bike-sharing is becoming increasingly popular as an urban traffic mode while increasing the affordability, flexibility, and reliability of interconnected public transportation systems (i.e., interconnected light rail, buses, micro-mobility, and ride-sharing modes of transportation). From the consumer’s perspective, (1) finding a bike station in convenient locations where demand usually occurs and (2) the availability of bikes at rush hours with a lesser probability of encountering empty docks (for fixed-station bike-share systems) are two key concerns. Some stations are more likely to be empty or full, reflecting an imbalance in bike supply and demand. Accordingly, it is essential to understand a bike-share system’s demand pattern to select the optimal locations and reallocate bikes to the right stations to increase the utilization rate and reduce the number of unserved customers (i.e., potential demand). The Capital Bikeshare in the Washington DC Metropolitan Area is one of the prominent bike-share systems in the USA—with more than 4300 bikes available at 654 stations across seven jurisdictions. This study provides a systematic analysis of a bike-sharing system’s Capital Bikeshare system usage pattern. Our study intends to create an optimization strategy formulated as a deterministic integer programming for reallocating bike stations daily and rebalancing the bike supply system. From an operational perspective, such a strategy will allow overnight preparations to answer the rush-hour morning demand and during special events in Washington D.C.

Pedram Beigi, Michel Khoueiry, Mohammad Sadra Rajabi, Samer Hamdar
Needs of Autonomous Vehicles for Safe Operation on Existing Highways

Autonomous vehicles (AVs) will gradually supersede human-driven vehicles (HDVs) in the future. Unlike human drivers who perceive their surroundings with their eyes, AV senses the ambient environments based on sensor fusion. More specifically, light detection and ranging (Lidar) sensors, video cameras, and radars are combined to help AV understand their surroundings. Current highway geometric design elements are mainly based on human driver-related parameters, such as perception and reaction time (PRT). However, AV will mix with HDV on existing highway infrastructures during the transition period. This study focuses on the sight distance aspect of highway geometric design. It is unsafe if an AV cannot effectively detect the objects within its required sight distance using the fused sensing system. Therefore, determining the needed sensor configurations (e.g. height, effective range, and field of view) is necessary for safe AV operation. This study used a simulation approach to determine the needed sensor configurations. First, the required stopping, decision, and passing sight distances for AV were determined considering that AV has a much shorter PRT than HDV. Second, the automated driving toolbox of MATLAB was used to construct different scenarios, each involving the road, obstacles, and actors. The road models were created following current design guides. A virtual AV equipped with a Lidar, cameras, radars, and an impeding agent served as the main actors on each road model. Third, many simulations were conducted with different sensor configurations to determine the Lidar configuration that achieves 100% detection for the safe operation of AV on existing highways.

Said M. Easa, Yang Ma, Azam Alaei, Harsheev Desai, Lee Weissling
Evaluation of Dynamic Incentive Pricing for Congestion Management in Transit System: An Agent-Based Simulation

This paper analyzed the feasibility of a dynamic fare incentive strategy by characterizing commuters’ travel patterns and the extent of their flexibility in departure times using multi-source data. In the proposed fare incentive, commuters incur a surcharge during the central peak period and obtain a monetary reward during the shoulder peak period. The fare incentive determines central period location and length, the value of reward and the reward ratio which is the ratio of the number of trips with reward to total number of trips. We proposed an agent-based simulation to evaluate the performance of the fare incentive inclusive of outlier analysis, travel pattern recognition, and crowdedness interpretations. The simulation and evaluation are applied to a metropolitan transit system using smartcard and operation data. Results reveal the practicality of the proposed fare incentive to reduce the congestion by affecting commuter departure time distribution while keeping the flexibility interval unchanged.

Yili Tang, Bingyu Zhao
Hybrid Simulation-Based Resource Planning and Constructability Analysis of RCC Pavement Projects

One of the critical challenges in infrastructural constructions is designing and planning operations and their related resources. The complex interlinked composition of different factors and variables affecting resource productivity has made simulation a powerful approach for operational planning. The construction sector has recently seen a notable surge in applying various simulation tools to enhance further the quality of projects’ planning, particularly in large-scale infrastructure developments (e.g., highway construction). Due to possible cost overruns in improper resource allocation, optimizing the design and construction planning stages of megaprojects such as massive pavement projects is essential. Recent studies aimed to build a simulation-based strategy in construction designing and planning by combining various simulation approaches (e.g., discrete-event simulation, system dynamics, agent-based simulation, and hybrid simulation) to enhance the planning phase. This paper introduces an evolving real-time hybrid simulation technique regarding the project's intrinsic time-varying inputs and factors to optimize the planning of Roller-Compacted Concrete (RCC) pavement projects. Several scenarios are investigated using various resource combinations to achieve the best execution method for delivering concrete to the project. An actual highway project case study validates the proposed model and its application for future projects. This study's findings exhibit the proficiencies of the simulation-based approach in resource planning of RCC pavement projects within the time and cost constraints and their related regulations.

Mohammad Shakerian, Mohammad Sadra Rajabi, Mohammad Tajik, Hosein Taghaddos
Comparative Analysis of Intersection Data Derived from INRIX and GRIDMART

With an increase in transportation funding, the need arises to implement analytic tools to measure the effects of improvements and guide decisions regarding the effective planning and design, as well as the operation of streets. Recent advances in intelligent transportation systems (ITS) and data collection made available high volumes of data from multiple data sources. However, a significant challenge remains in digesting and understanding the large and complex data available. In the specific case of intersections, the estimation of performance metrics is challenging due to the presence of different traffic control systems, multiple data sources and multimodal interaction. The principal objective of this research is to evaluate intersection performance metrics calculated using two different data sources and using Austin, Texas, as a case study. The evaluation is based on the fusion of INRIX data and GRIDSMART data. The main contributions include development of comparative intersection performance metrics combining two data sources, implementation of all required data workflows, and analysis of the fusion of GRIDSMART data and INRIX data. The analyses suggest that while total volume estimates provided by INRIX are not likely to be accurate, and discrepancies with GRIDSMART data are larger than 20% in most analyzed cases, differences in turning movement ratios yielded more promising results with differences between the two data sources generally less than 10%. Those results provide information that can help practitioners select an appropriate methodology for evaluating intersection performance.

Maria Bassil, Natalia Ruiz Juri, Randy Machemehl
A Study on the Mobility Pattern of Slum Dwellers in Dhaka, Bangladesh

Dhaka is the capital and one of the oldest cities of Bangladesh, mostly renowned as the economic and business hub of the economy of the country. Transport studies on Dhaka, the capital and primate city of Bangladesh, do fairly reflect on the overall mobility scenario of the city. However, there is a paucity of literature on the subject for the four million people who live in slums. Furthermore, most of the extant gray literature contradicts itself, claiming that many slum people utilize rickshaws and other non-motorized vehicles. As a result, low-income people’s mobility needs are frequently disregarded in transportation policies and programs. This study summarizes the findings of the movement pattern of inhabitants of four slums in Dhaka in order to make an empirical contribution in this area. The majority of slum inhabitants’ routine excursions are for employment, with 58% taking place on foot, followed by rickshaws (12%), bicycles (6%), boats (7%), public buses (6%), and scooter/tempo (6%) (11%). Slum residents walk because they cannot afford to pay for transportation. They also visit their families on occasions, such as during festivals and other holidays. Gender differences in transport mode selection were observed. The most influential criteria for slum residents’ mode choice behavior include household income, distance, trip cost, journey time, and so on.

Ayesha Siddika, Kazi Ehsanul Bari, Md. Musleh Uddin Hasan
Towards Data-Informed Sub-Models for Pedestrian Microsimulation of Transportation Terminals

Pedestrian microsimulation software is used to model and evaluate the circulation of pedestrians in transportation terminals. It can be used to determine potential travel times and visualize congestion during the design phase so that change and optimization can be made. Model parameters can also easily be changed to simulate a variety of scenarios, including peak travel times, events, and emergency evacuations. These models can be augmented and extended through the use of Software Development Kits (SDKs), including the introduction of new behaviours via modifications to the movement algorithm. However, these extended sub-models require validation. This presentation uses a study of a transportation terminal to demonstrate the evolution of a Pedestrian Microsimulation Sub-Model for group behaviour, the importance of real-world validation data, and potential data collection methodologies. Multiple versions of the group forces model are demonstrated as implemented within the pedestrian microsimulation software MassMotion, starting from initial concepts through to full implementations of potential group movement algorithms. Preliminary data collection efforts in an intercity transportation terminal are discussed, including the benefits and drawbacks of extracting movement and behavioural data from prerecorded video. New modifications to open-source motion tracking software will be demonstrated and compared with LIDAR and manual notetaking methods. Finally, a path forward will be discussed for employing video data analysis to assist with calibration, verification, and validation of Pedestrian Microsimulation Sub-Models. With further development, the use of data-informed sub-models has the potential to include more accurate movement and behaviours in pedestrian modelling and allow practitioners and engineers to design buildings, pedestrian spaces, and transportation terminals with higher confidence in pedestrian flow results.

Timothy Young, John Gales

Transportation Specialty: Climate and Pandemic Resiliency

Bike Share’s Impact on COVID-19 Transmission and Bike Share’s Responses to COVID-19: A Case Study of Washington DC

Due to the wide-ranging travel restrictions and lockdowns applied to limit the diffusion of the SARS-CoV2 virus, the coronavirus disease of 2019 (COVID-19) pandemic has had an immediate and significant effect on human mobility at the global, national, and local levels. At the local level, bike-sharing played a significant role in urban transport during the pandemic since riders could travel outdoors with reduced infection risk. However, based on different data resources, this non-motorized mode of transportation was still negatively affected by the pandemic (i.e., relative reduction in ridership). This study has two objectives: (1) to investigate the impact of the COVID-19 pandemic on the numbers and duration of trips conducted through a bike-sharing system—the Capital Bikeshare in Washington, DC, USA, and (2) to explore whether land use and household income in the nation’s capital influence the spatial variation of ridership during the pandemic. Toward realizing these objectives, this research looks at the relationship between bike-sharing and COVID-19 transmission as a two-directional relationship rather than a one-directional causal relationship. Accordingly, this study models (i) the impact of COVID-19 infection numbers and rates on the use of the Capital Bikeshare system and (ii) the risk of COVID-19 transmission among individual bike-sharing users. In other words, we examine (i) the cyclist’s behavior as a function of the COVID-19 transmission evolution in an urban environment and (ii) the possible relationship between the bike-share usage and the COVID-19 transmission through adopting a probabilistic contagion model. The findings show the risk of using a bike-sharing system during the pandemic and whether bike-sharing remains a healthier alternative mode of transportation in terms of infection risk.

Pedram Beigi, Mohaiminul Haque, Mohammad Sadra Rajabi, Samer Hamdar
What Can We Learn from On-Demand Transit Services for Ridership? A Case Study at the City of Regina, Canada

The urgent need to optimize operational efficiency, boost ridership, enlarge effective communication technologies, and improve customer convenience has led to the emergence of on-demand transit (ODT) services. ODT can be advantageous in several ways, including reliability, improving mobility, cost-effectiveness, and reducing the need for multi-transit services. This paper analyzed the trip patterns of on-demand services and the impacts on ridership by the difference-in-difference method. The pattern analyses showed that the origin–destination flow patterns are concentrated in large commercial and dense residential areas with significantly reduced travel times including the waiting times and in-vehicle times. Furthermore, the difference-in-difference model analyses yielded positive relations between the ridership and the on-demand transit services for the overall transit network while the effects vary with specific landuse zones. Results indicated the potential of on-demand transit services to benefit passengers and ridership recovery during the pandemic and post-pandemic.

Yili Tang, Duha Abdullah, Adesola Adewuyi, Nathan Luhning, Satinder Bhalla
The Impact of Curfew on Transit Demand and In-Vehicle Density

Many countries have implemented a restriction on the operation hours of restaurants and bars at night during COVID-19 to curb the spread of the virus. In Canada, transit demand has plunged significantly during curfew hours. Seoul also implemented a similar type of restriction and cut the number of operating buses by 20% after 9 p.m. The impacts of the restrictions on transit demand and in-vehicle density varied according to transit mode, time, and location. This study aims to analyze the impacts of the restrictions using Seoul smart card data from August 24 to September 11, 2020. We observed several significant findings regarding changes in transit demand patterns. First, the demand from 9 p.m. to midnight shifted to alternative departure times. Second, there was a curfew rush hour at approximately 9 p.m., when many people rushed home simultaneously, increasing volumes by 34%, while transit demand after 9 p.m. plunged by 30% compared to before curfew periods. Third, passengers showed different sensitivity to their transit modes. This is because they understood the frequency of bus operations would be reduced as a part of the restriction. Fourth, the curfew rush hour demand emerged in high-density socializing establishments. Lastly, due to the curfew rush hour effect, in-vehicle density significantly increased on certain bus routes, potentially endangering passengers by spreading the virus. These findings provide insights for implementing restrictions on transit operation and pandemic preparedness planning.

Haesung Ahn, Sungho Lim, Yong Hoon Kim
A Review of the Application of Hybrid Models in Flood Risk Assessment Methods

Transportation networks, which are vital to society’s function, are vulnerable to extreme events like floods. Under the influence of climate change, the intensity and the frequency of these food events are increasing globally at an alarming rate. These events result in a series of flood impacts and associated cascading effects, which reduce the overall resilience of the road network. Flood risk assessment methods, which are applied to analyze these impacts are almost always associated with hybrid methods/models, which improvise the overall assessment methodology and impact quantification. The present article is a short review of the hybrid models like GIS-based models, cellular automata, traffic simulation, and input–output models, which are the most applied in the flood assessment methods. Of these models, GIS-based models have wide range of applications and depict the impacts in spatial scale. The Calgary floods of 2013 is used to display the spatial impact and flood prone/risk areas.

Aditya Rebally, Caterina Valeo, Jianxun (Jennifer) He, Saeid Saidi
Assessing Risk of Climate Change on Existing Canadian Bridge Infrastructure: A Multidisciplinary Approach

Addressing the impact of climate change on transportation infrastructure is one of the global challenges of this century. The impacts of climate change are visible across the globe and have been growing progressively worse over the last 50 years. The climate in North America will continue changing during the twenty-first century; current predictive models indicate that the mean annual temperature will rise by between 1 and 5.5 °C. Annual precipitation is likely to increase by up to 5% in most Canadian regions, while the intensity of daily precipitation and the probability of extreme precipitation intensities may increase across the entire country. Mean annual and extreme wind speeds are expected to increase and the sea level in some areas is likely to rise by up to 0.9 m by the end of the century. These changes create an environment of uncertainty when assessing the risk of climate change on existing bridge structures. In collaboration with the National Research Council, this is ongoing research which requires much effort in assessing the risk and developing a tool for engineers to assess existing bridges. A risk assessment tool is developed to equip practicing engineers and decision-makers with the challenging task of evaluating bridges structurally while considering the impact on socioeconomics. The presented protocol incorporates projected temperature values based on representative concentration model 6.0 (RCP 6.0) as outlined by the Intergovernmental Panel on Climate Change (IPCC). The methodology developed evaluates the impact of projected temperature on a given bridge both structurally and socioeconomically. This tool allows decision-makers to evaluate a portfolio of bridges to determine the level of risk and provides input toward prioritization of intervention projects and, therefore, resource allocation. The methodology is a systematic multidisciplinary approach that can be applied to assess existing bridges considering climate change.

Shereen Altamimi, Lamya Amleh, Liping Fang

Materials Specialty: Advanced Composite Materials and Technology

Rheological Properties of Geopolymer Mortars Incorporating Construction and Demolition Wastes-Based Binders and Aggregates

The re-utilization of construction and demolition wastes (CDWs) in the emerging geopolymer technology has been recognized as an environmentally friendly solution for tackling the ecological challenges caused by the increased landfilling of CDWs and sustainability issues of Portland Cement (PC) production. Geopolymers are synthesized as a result of intricate chemical interactions between aluminosilicate-based precursors and highly alkaline solutions resulting in the production of amorphous inorganic geopolymers possessing three-dimensional cross-linked networks of Si–O–Al and Si–O–Si bonds. The aim of this study is to investigate the effect of incorporating different types of aggregates including recycled concrete aggregates sand (RAS), silica sand (SS) and natural sand (NS) on the rheological properties of geopolymer mortars (GPM) prepared from CDW-materials comprising a combined powder mixture of recycled clay brick (RCB), recycled ceramic tile (RCT) and recycled concrete (RCW) wastes as silico-aluminate binders. Yield stress, viscosity and shear stress were tested at 100% of RAS, SS and NS contents in GPMs prepared with sodium silicate and sodium hydroxide solutions as alkaline reagents and predefined chemical design factors of SiO2/Al2O3, Na2O/SiO2, H2O/Na2O and water-to-binder (W/B) ratios. The correlation between the rheological properties of GPMs and the predefined design parameters was considered. The highest yield stress and viscosity were obtained at medium SiO2/Al2O3 molar ratio of 5.6 for all three GPM systems, while further increase in silicate species caused reduced stresses and viscosities. Comparable shear thinning behavior, higher viscosity and accelerated polycondensation properties were observed with increased RAS amounts compared to SS and NS.

Obaid Mahmoodi, Hocine Siad, Mohamed Lachemi, Sina Dadsetan, Mustafa Sahmaran
Applications of Recycled Gypsum from Waste Drywalls in the Construction Industry: A Review

Reusing and recycling construction and demolition waste materials are one of the main approaches to reduce the environmental impacts of the construction industry. Waste gypsum drywalls from ever-growing renovation projects and scrap drywalls from new constructions have become a major issue for municipalities. Several researchers have studied the potential use of recycled gypsum from waste drywall as a second-raw construction material, especially for concrete construction. However, there is no comprehensive review study on the topic while it can identify research gaps and provide a direction for future studies. With this background, this review paper focuses on the applications of recycled gypsum drywall (RGD) in the construction industry and its environmental and economic benefits. Additionally, this paper proposes the best mixtures for the concrete containing RGD through the literature review. The cementitious composite of this mixture can be used in other introduced applications. To this end, applications of RGD in the construction industry were classified into seven groups, including supplementary materials in concrete materials, soil stabilization, ceramic industry, recycled aggregates, cement production, plaster, as well as blocks and walls, and new achievements in each group were discussed. Then, the most eco-friendly concrete mixture with acceptable mechanical strength was proposed, assisting researchers in future studies. The results illustrate that reusing RGD can significantly reduce the carbon dioxide emissions of the concrete and provide economic benefits. A combination of ordinary Portland cement, recycled gypsum, fly ash or perlite, and slag was proposed as the most appropriate cementitious concrete composite.

Alireza Jafari, Pedram Sadeghian
A Study on the Mechanical and Durability Properties of Rubberized Concrete

Even though concrete is a huge contributor to global greenhouse gas emissions, it has become an indispensable part of our everyday life. The use of recycled materials in concrete has the potential to provide an eco-friendly solution to concrete construction technology and reduce its carbon footprint to some extent. Research has been carried out for decades to make concrete an environmentally friendly material and the inclusion of rubber crumb as a replacement for aggregate is gaining popularity in recent times. This also solves the disposal problem of scrap rubber tires which is a serious concern considering the huge market of rubber tires all over the globe. Contrasting results are observed in previous research on the effect of crumb rubber in concrete. Moreover, a proper guideline is necessary for incorporating rubber crumb in concrete as its properties vary with the origin of the rubber scraps. To determine an optimum replacement level of crumb rubber in concrete, this study investigated the properties of cement concrete made with crumb rubber replacing particles at levels 10, 30, and 50% with fixed water-to-cement ratio of 0.31. Concrete properties that were examined in this comprehensive study include fresh property: slump and mechanical properties: compressive strength and failure pattern. It was observed that up to 10% replacement of sand with crumb rubber in concrete resulted in comparable mechanical properties.

Rubaiya Rumman, Salamah Meherier, Mohammad Tiznobaik, M. Shahria Alam
Effect of Ultrafine Granulated Blast Furnace Slag on the Strength Development of Portland Cement Mortar

The current study evaluated the effects of ultrafine granulated blast furnace slag (GBFS) on the compressive strength development of Portland cement mortar. The previous studies have investigated the effects of ultrafine slag (UFS) with sizes of around 3–5 μm on the concrete performance. Despite the great potential of smaller size GBFS particles to enhance the concrete performance, such effects are not clearly known. In this study, UFS particles with sizes of around 1 and 0.6 μm were prepared using a planetary ball mill. UFS was then used to replace Portland cement by 5, 10, and 15 wt.% in preparing mortar specimens. The compressive strength of the specimens was measured at different ages. Isothermal calorimetry was also used to provide insight into the strength development mechanisms of specimens. The results showed that UFS powders significantly increased the 1-d and 3-d compressive strength of mortar specimens by up to 46 and 52%, respectively. The compressive strength increase was proportional to the replacement level of Portland cement with UFS powders. Compared to the 1 μm UFS, only a minor enhancement in 1-day compressive strength of the specimens containing 0.6 μm UFS was observed. The 28-day compressive strength of all specimens was similar regardless of their UFS content. The isothermal calorimetry results showed that the UFS powders increased the early hydration rate of Portland cement. A preliminary analysis of energy consumption of UFS preparation showed that partial replacement of Portland cement with UFS could result in cementitious binders with less GHG emission.

Saeid Ghasemalizadeh, Rahil Khoshnazar
Mechanical Performance of Concrete Incorporating Waste Glass Fiber-Reinforced Polymer Materials from Recycled Wind Turbine Blades

This paper presents the results of an experimental study on the effects of the addition of waste glass fiber-reinforced polymer (GFRP) materials from wind turbine blades (WWTB)—designated as WWTB-GFRP—into concrete as fiber reinforcement. Compressive and flexural strength and flexural toughness of concrete cured in standard conditions for 28 days were investigated. Fiber addition rates of 1–1.75 vol. % have been used for two types of WWTB-GFRP: with wood component and after wood removal. According to the test results, the increase in the WWTB-GFRP fiber content leads to a slight to negligible decrease in compressive strength of 6% maximum (for 1.75% of fibers with wood added), an increase in flexural strength up to 22% (for 1.75% of fibers added after wood removal), and an increase in flexural toughness by more than 4 times (for the mixture with 1.75% of fibers without wooden content). Mixtures containing fibers without wood content demonstrated better results in all tests. In general, the results presented in this paper support the use of WWTB-GFRP material as fiber reinforcement in concrete.

Dmitry Baturkin, Ousman A. Hisseine, Radhouane Masmoudi, Arezki Tagnit-Hamou, Slimane Metiche, Luc Massicotte
Partial Cement Replacement in Concrete with Gypsum Powder Recycled from Waste Drywalls

Construction industry is one of the most significant contributors to environmental issues in today’s world. For this reason, sustainable approaches in building industry have always been sought by researchers in this domain. Cement manufacturing process, for example, emits considerable amounts of greenhouse gasses contributing to global warming. Replacing cement with other materials which have less environmental footprints has been considered a solution. Construction and demolition waste disposal, also, could cause environmental issues in landfills. Gypsum drywalls account for a considerable amount of construction waste which contains a noticeable amount of gypsum. Utilizing recycled gypsum from waste drywalls as a partial replacement for cement in concrete could address both problems regarding the impact of construction on the environment. In this study, recycled gypsum powder from waste drywall will be used as a partial replacement for cement in concrete. Five concrete mix designs which include 0, 10, and 20% of recycled fine gypsum powder and whole gypsum are considered for this study. Since it has been proven that gypsum does not function well as the only partial replacement of cement, 50% of each mix design is dedicated to fly ash. Three cylindrical (100 mm × 200 mm) specimens of each mix design are planned to be tested at 7, 28, and 90 days. This paper will introduce the combination of fly ash and recycled gypsum as a sustainable replacement for cement in concrete and suggest more environmentally friendly concrete for our infrastructure.

Kasra Takbiri, Pedram Sadeghian

Materials Specialty: Innovatinve and Emerging Materials

Converting Other Flexible Plastic Packaging into Fiber Reinforcement for Concrete Structures

Concrete is world’s most common construction material owing to its unique formability where it is typically reinforced with steel rebars. Nevertheless, the high tensile strength of steel rebars is usually localized, and rebars are prone to corrosion creating deterioration of infrastructure costing billions of dollars for repairs. This has resulted in using fibers into concrete called fiber reinforced concrete (FRC). This replacement technology (i.e. FRC) not only improves the quality of concrete, but it is also environmentally friendly. Most commonly, steel, glass, synthetic cellulose, carbon, etc. are used as fiber for FRC. Aside from these, this research presents the use of other flexible plastic packaging (OFPP) as reinforcement in concrete. OFPP is one of the fastest growing types of packaging, which is not easily recyclable as it comprises multiple layers of different kinds of plastics. Examples of OFPP includes stand-up/zipper lock pouches, crinkly wrappers/bags, flexible packaging with plastic seal, non-food protective wrap, net bags for onions, avocados, etc. The major steps involved in this formulation include the sorting and cleaning of OFPP (as waste) to obtain clean and usable material, which is then shredded into fibers. Upon employing a patented coating technology developed at UVic, these shredded fibers are converted into green engineered surface-treated fibers (GESTF) for casting different concrete structures, namely FRC. In order to access the performance of FRC thus obtained, a set of mechanical testing is conducted according to ASTM/CSA test standards. On accomplishing the tests, a significant improvement in concrete structure is observed in terms of compression, uniaxial tension or indirect tension, flexure, and plastic shrinkage. This research will potentially open-up a new market and process for using OFPP for improving the mechanical and early-age shrinkage properties of concrete.

Loveleen Sharma, Jaykumar Viradiya, Rishi Gupta, Sam Baker
Novel Green Mortar Incorporating Crumb Rubber and Wood Fly Ash

Increased repercussions from climate change have popularized research into ways of mitigating the environmental impacts of construction processes. The production of building materials is a key concern, with the cement industry accounting for a considerable amount of global greenhouse gas emissions. Exploitative sand mining for use in infrastructure also has negative environmental impacts. The harmful effects of concrete would improve by reducing the cement and sand used in its production. Moreover, as coal plants become obsolete, coal fly ash will no longer be available and should be replaced. The purpose of this paper is to explore the behavior of mortar mixtures made with wood fly ash and crumb rubber as cement and sand replacements, respectively. The use of post-consumer waste tires as crumb rubber enhances the sustainability of these mortar mixtures by reducing the quantity of sand used. Furthermore, it eliminates the build-up of tires in landfills, which is a growing concern globally. In the samples cast, an aqueous sodium hydroxide solution-treated crumb rubber replaced 10 and 20% of the sand. Wood fly ash was used in conjunction with the crumb rubber. It substituted 15 and 30% of the cement used in the control mixture. Nine mortar mixtures were cast and tested under compression to demonstrate the effects of the combination of various materials and their failure patterns. Casting and compressive tests followed CSA standards. The microstructure of the samples was studied using scanning electron microscopy. The color of the mortar is of interest and has also been analyzed. Reducing the quantity of cement and sand used to produce mortar reduced their environmental impact. Results of the study show that incorporation of wood fly ash up to 30% can produce mortar with satisfactory strength. Although crumb rubber addition significantly reduces the mortar strength, it can still be used for constructing non-load-bearing structures. The use of wood fly ash and crumb rubber is a viable solution to the obsolescence of coal fly ash and increasing volume of tire wastes.

Samantha Krieg, Rubaiya Rumman, Meraj Rubayat Kamal, Ahmed Bediwy, Kishoare Tamanna, M. Shahria Alam
Algorithmic Mix Design for 3D Printing Materials

Additive manufacturing technology aims to revolutionize the construction sector. Researchers are looking for the optimum materials to use in mix design to control the fresh and final properties of the mix. Those properties are contradictory to each other, and finding the optimal mix design has always been a challenge. Developing an optimization tool that considers trade-offs among a variety of competing objectives can improve the mix design process. In this study, the mortars contained combinations of multiple factors, including the cement type, sand type, water content, and admixtures. Three properties investigated are flowability, buildability, and compressive strength. The buildability was assessed by measuring the shear stress with the direct shear apparatus based on the ASTM D3080. The workability was acquired by measuring the flow spread of the mortar mixes following the ASTM C1437, and the compressive strength following the ASTM C109. A multiobjective Pareto optimization method is used to improve the properties simultaneously. Feedforward neural networks were used to predict the properties of new mixes. The genetic algorithm was used to optimize the network parameters. This approach yields promising capability to improve the competing objectives of the mortar mixes by considerably reducing the time and the number of experiments.

Vasileios Sergis, Claudiane Ouellet-Plamondon
Sustainability Analysis of Structural Materials Used in Multistoried Building Construction: A Cradle to Grave Approach

Over time, the construction industry’s development has been constantly questioned due to low productivity, high energy consumption, generation of wastes, and greenhouse gas emissions. According to a recent United Nations Environment Program report, building and construction account for 36% of global energy use and 39% of energy-related carbon dioxide (CO2) and greenhouse gas emissions. Sustainable construction aims to minimize harm and maximize value by balancing social, economic, technical, and environmental aspects, commonly known as the pillars of sustainability. In general, concrete, timber, steel, masonry, etc., materials are used to construct multistoried buildings. Though technical and economic aspects are always considered while selecting the structural components, other elements like social and environmental are mostly ignored. A sustainable decision is always critical as it combines all technical, social, economic, and environmental factors in the decision-making process. On the contrary, though it seems crucial during the planning and conceptual development phase and costly while designing and construction, a sustainable choice is always more economical, eco-friendly, and convenient, considering the entire life cycle of any construction work. This paper analyzed the characteristics of commonly used structural materials from the sustainability point of view, considering the project’s complete life cycle. We have followed a hybrid approach to analyze life cycle sustainability analysis by integrating the outcomes obtained through life cycle cost analysis, environmental life cycle analysis, and social life cycle analysis and taking the opinion of stakeholders. The outcome of the analysis is expected to enhance objectivity in the selection process of structural material by the decision-makers contributing to more sustainable building construction.

Mohammad Masfiqul Alam Bhuiyan, Mohammad Rezaul Karim, Ahmed Hammad
Optimization of Pervious Concrete Mechanical Properties Through Incorporation of Fiber Reinforcement Schemes

Portland Cement Pervious Concrete (PCPC) is a special high porosity concrete containing zero or minimal amount of fine aggregates. Such concrete endows the concrete to have significant voids allowing water to percolate; however, such an open void structure reduces the mechanical strength of the concrete considerably. It is recommended that chemical admixtures be added to the concrete to enhance its workability and other properties. The study aims to potentially enhance the properties of PCPC through the incorporation of various fiber reinforcement schemes. The fibers used in the scope of this study are hooked-end steel fiber, macro-polypropylene fiber, and glass fiber. To meet that objective, concrete mixes were prepared using varying fiber dosage rates and aggregate gradations. An experimental program was developed to test fresh concrete properties, hardened concrete properties, and durability. In order to gauge only the effectiveness of the aforementioned fiber, the PCPC mix design was standardized across the spectrum to eliminate such variables. It was evident that the glass fiber with Vf 0.17% (GF 2) enhanced mechanical properties with the most significant compressive strength increase, compared to the control sample, reaching 34 MPa. Moreover, (GF 2) has enhanced, compared to the control sample, the flexural and the splitting tensile strength with an increase of 93.7% and 161.9%, respectively. The outcome of the study is that the use of different fiber reinforcement schemes has managed to enhance the mechanical strength of PCPC while maintaining an adequate rate of infiltration that complies with ASTM standards. The research opens the door for further application of the proposed model in different contexts both regionally and internationally, thus playing a vital role in the concrete nexus.

Adham Sherif, Ahmed Koura, Amir Ibrahim, Amr El Sayed, Aya El Kayyal, Donia ElDwib, Mayer Farag, Mohamed Abou-Zeid

Materials Specialty: Cement and Concrete

Chopped Fibre Dosage and Material Effects on the Fresh Properties of Normal Strength and Density Concrete

Chopped fibre reinforced concrete (CFRC) is used in many applications, including shotcrete tunnel walls, bridge decks, pavements, and concrete slabs. Cracked concrete’s service performance can be improved using chopped fibres. The influence of chopped fibre type and volume on fresh concrete properties and mixture design was investigated in this study. Trial mixtures were used to optimize a mixture initially developed using the American Concrete Institute’s absolute volume method. Ten normal strength and density test mixtures were then prepared based on these optimized trial mixtures. Mixtures included one control (i.e. no fibres) and nine CFRC mixtures. Mixture parameters included chopped fibre type (steel, glass, and a combination of the two) and fibre dosage (0.5, 1.0, and 1.5%). The bulk fresh, one-day dry room temperature, and 28-day humidity room densities were obtained from 10 cylinders in each mixture. Workability was measured using both slump tests and Ve-Be time tests. Results show significant reductions in slump with increased fibre content, and glass fibre mixtures had less workability than steel fibre mixtures. The hybrid steel and glass fibre mixtures allowed for further study of each fibre’s effect on workability. There was a good correlation between the slump and Ve-Be time results for mixtures with low fibre dosages, but Ve-Be time tests were found to be more appropriate to assess the workability of stiff concretes such as those with a high dosage of glass fibres. Both fresh and dry densities of CFRC cylinders increased due to adding steel fibres, and there was a minor reduction in these densities of glass fibre cylinders. Outcomes of this study will provide concrete mixture designers and structural engineers with additional guidance on mixture design and proportioning for CFRC to obtain desired fresh properties.

Helmi Alguhi, Douglas Tomlinson
Fiber Effects on Phase Change Materials Concrete Properties

In the era of environmental concerns, the increase in the buildings’ operating energy has necessitated the finding of efficient technology to reduce their energy losses. Incorporating phase change materials (PCMs) into building materials (i.e., concrete) had been adopted as a promising solution. However, adding PCM to concrete showed detrimental effects on its properties, mainly reduction in the mechanical properties. Hence, this study investigates the potential of overcoming this issue by adding fibers. Several types of fibers were added at rates 0.0, 0.5, and 1.0% by volume of the mixture and tested. Results showed that adding fiber to PCM-concrete had improved the mechanical properties, regardless of the fiber types and additional rates. The higher the fiber content, the higher the improvement in PCM-concrete properties. Also, the stiffness and geometry of the fiber had significant effects. Bridging voids induced by PCMs breakage and increasing tensile strength of the matrix enhanced the achieved strength. The findings of this study pave the way for higher PCMs incorporation leading to better thermal performance.

Mahmoud Rady, Ahmed Soliman
Analysis of a Corrosion Failure of Prestressed Concrete Cylinder Pipe: A Pilot Study

This paper presents the findings of a pilot study designed to better understand the underlying causes of the high failure rates of the Prestressed Concrete Cylinder Pipe (PCCP) used in the semi-arid regions of Morocco. The study used mini-pipes (made of mortar coating and reinforcing steel) immersed in basins to simulate their performance in a near real-life service environment. Four basins were evaluated: Basin 1 (control basin) contained the control soil, whereas the other three basins contained chemically enriched soils (Basin 2 with sulfate solution; Basin 3 with chloride solution; and Basin 4 with combined chloride-sulfate solution). Each basin had four mini-pipes made from OPC mortars and a PCC mortar with 17% fly ash. In this paper, electrochemical impedance spectroscopy (EIS) technique was used to assess the corrosion process of the reinforcing steels specimen while a scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM/EDX) was used to study the steel-mortar interface. The preliminary results revealed, as expected, that the mini-pipes in Basin 4 had the highest corrosion rates. It was also found that the PCC mortar with 17% fly ash produced the best corrosion performance results in all four basins, implying that if used, can significantly improve the service life of pipes in semi-arid regions.

Sara Hassi, Aadil Ejbouh, Bruce Menu, Mouhssine Galai, Adil Ech-chebab, Mohamed Ebn Touhami, Hanane Benqlilou
Reducing Chloride Induced Corrosion Risk and Associated Life Cycle Cost of Marine RC Structure: Bangladesh Perspective

Chloride induced corrosion poses significant threat to Reinforced Concrete (RC) structures in marine environment. Therefore, proper design of marine RC structures in terms of materials types, mix proportions, and concrete cover is prerequisite for ensuring adequate durability and sustainable construction practice. Inappropriate selection of mix proportions, mix constituents, and concrete cover can significantly hamper the expected service life of a marine RC structure and eventually, results in substantial repair costs. In this study, an attempt was made to investigate the effect of binder types on corrosion risk and corresponding life cycle cost of RC slab or wall made of locally used construction materials of Bangladesh under extreme marine conditions. Five different types of binder (combinations of ordinary Portland cement and 20%/40% replacement level of slag/fly ash) and two w/b (water to binder) ratios of 0.35 and 0.45 were used along with three concrete cover values of 19 mm, 25 mm, and 37.5 mm to perform the parametric study. The Life-365 environment was used to evaluate chloride induced corrosion risk and the associated life cycle cost of RC slab or wall structure made of considered concrete mixes for a design service period of 100 years. It was evident from the study that the type of binder, use of fly ash in particular, could have considerable impact on corrosion proneness of concrete mixes. The use of a typical cover value of 19 mm for RC slabs/walls was inadequate in providing satisfactory performance under extreme saline exposure even if a higher percentage replacement of fly ash is used. The benefit of using higher concrete cover and blended cement with a higher percentage of fly ash in a saline environment was also quantitatively apparent from this study in the context of Bangladesh. Moreover, life cycle costs of marine RC structure could be significantly reduced by utilizing higher cover values and blended cement with fly ash.

Tanvir Manzur, Munaz A. Noor, Tafannum Torsha
Microstructural Investigation of Coupled Sulfate and Freeze–Thaw Damage of Concrete Using Micro-Computed Tomography

Concrete structures in sub-zero temperatures can be severely damaged due to freeze–thaw cycles. The damage can be aggravated if the concrete is exposed to different sulfate environments. The damage is observed at a macroscale level; however, little attention has been paid to investigating the damage at the microscale level representing the early stage of damage. Therefore, the focus of this investigation is to study the microscale damage mechanisms of concrete subjected to up to 80 freeze–thaw cycles in different environments: water, potassium sulfate, and magnesium sulfate with 5 and 10% concentrations. It was observed that exposure to potassium sulfate significantly accelerated the frost damage leading to a complete disintegration of the samples, whereas the control specimen lost about 20% of its mass after 80 cycles. However, the typical mechanisms of frost damage were not altered, where the scaling damage started at the external surface and propagated toward its core. On the other hand, subjecting concrete to magnesium sulfate mitigated the severity of frost damage and changed its mechanisms, resulting in more expansion within the internal pores than the surface ones. Hence, the average mass loss of concrete after 80 freeze–thaw cycles in the magnesium sulfate environment was only 1.38%. Also, increasing the concentration of magnesium sulfate produced more frost damage.

Mustafa Alhusain, Adil Al-Mayah
Vacuum Mixed Concrete

Vacuum mixing concrete results through the creation of a vacuum chamber by removing the air to introduce a vacuum medium through which concrete will be mixed. Mechanical and economic advantages as well as maintaining the well-being of the workers are amongst the advantages that can be expected from such concrete. In addition, this technique may reduce the mechanical effort needed to remove excessive bubbles within the concrete during the compaction stage. This may help in reducing resources and minimizing costs. The objective of this study is to explore the feasibility of producing vacuum mixed concrete by assessing its properties, and the environmental impact of its use in construction. To meet this objective, different concrete mixtures were produced using two w/c ratios: 0.40 and 0.55 while adjusting key parameters including the mixing time and the suction capacity. Fresh and hardened concrete tests as well as durability tests were introduced to evaluate the properties of the vacuum mixed concrete produced. Results reveal that vacuum mixed concrete can be produced using an adequate suction pump while adjusting parameters such as the pressure as well as the vacuum mixing time. Promising results in terms of enhancement of quality of such concrete are obtained which paves the floor for wider scale introduction for such concrete in concrete mixing plants and projects upon further validation and evaluation of these results.

Mohamed Shahin, Omar Abdelmeguid, Ahmad El-Shantoury, Salma Ali, Hassan El Kassas, Reem Aboali, Mohamed AbouZeid
An Appraisal of Hydroplaning Pavement Surface Improvement Materials and Assessment Models

Wet pavement has always been a significant safety concern due to the rise in wet weather accidents. Each year, 70% of weather-related crashes happen on wet roads and 46% occur during precipitation. The reduced skid resistance and hydroplaning are two major challenges occurring in the wet pavement due to lack of surface friction. Curves, highways, intersections, single carriageway pathways, and four or higher-lane roads are more likely to experience hydroplaning and wet weather-related crashes. Previous studies suggest that the wet weather accident rate could be reduced by up to 70% by improving friction. This paper reviews the effectiveness of surface improvement materials, e.g., superhydrophobic materials, groove-filled pavement, etc. presented in recent papers to reduce the water film thickness and achieve suitable pavement friction properties. Previous review papers discuss the traditional empirical hydroplaning assessment models, such as the PAVDRN model, Gallaway model, etc., while few studies review the numerical models. In this paper, the traditional empirical and numerical models along with newly proposed hydroplaning models are discussed with references.

Faria Raha, Armana Huq, Zarrin Probha

Materials Specialty: Materials and Structures I

Design Methodology and Properties of Concrete Mixes Developed for an Underwater Repair Application

Designing a concrete mix which can be easily placed for underwater construction and repair of marine structures, while meeting strength and durability requirements can be an engineering challenge. This paper presents the design methodology and properties of a concrete mix used for an underwater repair project at a hydropower dam spillway repair located in Western Canada. Small-scale lab trials of different design mixes were initially batched to screen potential mix designs, according to properties including compressive strength, visual index, flow characteristics, and washout resistance. Based on the results, these trials were followed by larger scale mockup trials. These served not only to verify properties determined during the initial lab trials, but also to determine additional properties like abrasion resistance and capacity to bond to the substrate. Thereafter, a design was finalized to be used for on-site repairs. As per lab and mockup test results and observations, it was found that well-graded aggregates, higher paste contents, and optimal use of supplementary cementitious materials, such as silica fume and fly ash lead to high flow and ease of placement. Optimum amounts of high-range superplasticizing admixtures can also enhance the flowability, but excessive amount of superplasticizer can significantly increase bleeding. To enhance the washout resistance, use of an anti-washout admixture (water-soluble polymers with strong absorption capacity) and silica fume is also generally recommended. The type of aggregates used can also affect bleeding and flowability.

Sudip Talukdar, Negar Roghanian, Roland Heere, Neil McAskill
Interfacial Bonding of Nano-modified Cementitious Composites Incorporating Basalt Pellets to Normal Concrete

Interfacial bonding between precast normal concrete (NC) and cast-in-place high-performance fiber-reinforced cementitious composites (HPFRCC) has received significant attention in recent years, for applications such shear key fillers in bridge deck joints. Novel HPFRCC has been recently developed at the University of Manitoba. These composites include various constituents (cement, slag, nano-silica) and reinforced with fiber systems (single and hybrid) including polyvinyl alcohol (micro-PVA) and basalt fiber pellets (macro-BFP). BFP is a novel class of basalt fibers, where basalt fiber strands are coated by a polymeric resin with textured surface micro-grooves. In this study, the interfacial shear bond adhesion and coefficient of friction between the NC and HPFRCC were evaluated using bi-shear test and slant shear test, with an inclination angle of 33.7º with the vertical. The results showed that nano-silica had a significant effect at improving the interfacial bonding strength and coefficient of friction with NC. The addition of 1% micro-PVA fibers to macro-BFP (hybrid system) in the nano-modified composites led to a noticeable improvement in their interfacial bonding and coefficient of friction with NC, which suggests their promising use for future field applications.

Elhadary Riham, Bassuoni Mohamed
Monotonic and Cyclic Pullout Performance of Hooked-End Super Elastic Shape Memory Alloy Fibers and Steel Fibers Embedded into Concrete

The bond characteristics between concrete and reinforcing fiber play a significant role in the performance of fiber reinforced concrete (FRC) under various loading conditions. The present work experimentally examined the pullout resistance of double hooked-end NiTi and steel fiber from 35 MPa (NS–Normal strength) and 60 MPa (HP–high-performance) concrete under monotonic and cyclic loading to assess the potential application of NiTi fiber in concrete. A novel SMA fiber fabrication method that starts with heavy cold-working the wire, then bending to the desired shape and followed by heat treatment at 350 °C was used. The heat treatment enabled higher strain recovery, shorter stresses plateau length and higher energy dissipation under cyclic loading. Individual fibers were embedded into concrete matrix with an embedment length of 30 mm. Comparison between steel and NiTi fibers on the maximum load, average and equivalent bond strength, and cyclic energy dissipation were studied. The results showed that the unique super elastic property of the NiTi shape memory fiber can be utilized by providing 5D anchorage that could be used to produce FRC with significant crack closing and energy dissipation capacity. The SMA fibers showed lower average bond strength and slightly higher equivalent bond strength than the steel counterparts. The SMA fibers outperformed the steel fibers on re-centering and energy dissipation under hysteretic pullout loading.

Demewoz W. Menna, Aikaterini S. Genikomsou, Mark F. Green
Elastostatics of Spherical Capsules in Self-healing Cement Matrix

A rigorous solution for a liquid-filled spherical capsule in self-healing cement matrix with remote uniform strain or stress is presented. The capsule shell is considered as an elastic material, and the interface between the capsule and cement is simulated as imperfect elastic spring-type interface. The healing agent enclosed in the capsule is considered as incompressible fluid. The state of strain/stress in the capsule and on the capsule–cement interface are derived. Consequently, the failure modes of the capsule, being rupture or debonding on the interface, are determined. Numerical results demonstrate the significance of capsule design and imperfect interface on the failure modes of capsules. The model can be used to assess capsule properties, including shell thickness, diameter, and material properties, in the design of self-healing system.

Shannon Guo, Samir E. Chidiac
Shear Behaviour of Concrete Beams Retrofitted with Anchored CFRP Wraps at Elevated Temperatures

Different anchoring techniques such as metal plates and bolts, U-shaped FRP jackets, FRP anchors have been used to delay the premature debonding of the FRP sheets in strengthened concrete structures. Among these, FRP anchors are more suitable since they can be applied simultaneously with the FRP sheets and are corrosion resistant. Anchored FRP sheets have shown promising results for both shear and flexure strengthened RC structures under room conditions. Due to the changing climate, structures are now exposed to higher than usual temperatures, so it is important to understand the behaviour of these anchored FRP sheets under elevated temperatures. The current study examined the thermal behaviour of four large-scale shear-critical steel-reinforced concrete beams, one unwrapped and three strengthened with a single layer of CFRP sheet and CFRP anchors. The beams tested at room conditions were monotonically loaded to failure, while beams tested at elevated temperatures (40 and 60 °C) were first subjected to a combined sustained load and elevated temperature during the 24 h conditioning period and then monotonically loaded to failure at that temperature. The tests showed the failure of the unwrapped beam by the rupture of a steel stirrup leg and that of the strengthened beams by pull-out of anchors accompanied by debonding of FRP sheet. A single layer of anchored CFRP wrap improved the beam strength by about 96% at room conditions, 101% at a temperature of 40 °C, and 88% at 60 °C. The midspan displacement also increased by 133% as a result of FRP wrapping at room conditions while exposure to 60 °C reduced this improvement to only 68%. A comparative study was also carried out to evaluate equations available in different FRP standards for shear strength predictions.

M. F. Qureshi, S. A. Sheikh
Use of Electrochemical NDT Tests for Evaluating the Effectiveness of Cementitious Materials for Corrosion Repair of RC

For many years, electrochemical nondestructive testing (NDT) techniques have been utilized in the construction sector to examine the structural soundness and safety of many kinds of buildings. Half-cell potential, macrocell current, and linear polarization resistance are three distinct kinds of electrochemical NDT techniques described in this work to test RC resistance to chloride attack and to help develop solutions to improve the durability and hence the service life of RC structures. The effectiveness of these three kinds of NDT procedures is discussed, as well as the electrochemical processes that occur when three distinct types of cementitious repair materials are subjected to sodium chloride. The findings of this experimental investigation reveal that the three distinct forms of NDTs used to measure the performance of three different types of cementitious material restoration have a close connection in terms of outcomes. After monitoring corrosion of repair materials exposed to chloride attack using HCP for the duration of the testing period, it was discovered that there is a greater than 90% chance that no corrosion is occurring for Mix F. Similarly, during monitoring corrosion activity using the macrocell corrosion method, it was discovered that Mix F has the least amount of corrosion conductivity with a value of less than 5 Coulombs. Mix F had the lowest corrosion rate density utilizing LPR NDT, with a value of less than 1 µA/cm2. Using these three types of NDT techniques, the differences in performance among three different kinds of cementitious materials while in contact with a concrete substrate and subjected to sodium chloride were also observed. Other NDT approaches will need to be investigated further in order to elucidate the chemical composition of more efficient cementitious repair materials subjected to sodium chloride.

Perla Rodulfo, Rishi Gupta
Temperature Control and Crack Prevention Scheme for Tail Floor of Large Hydropower Stations in High-Altitude Regions

Temperature control and crack prevention for the tail floor of a large hydropower station are difficult in high-altitude regions. Therefore, research on fine temperature control and crack prevention according to climatic characteristics is necessary. Temperature stress and temperature control measures for the tail structure of a hydropower station in a high-altitude region are studied based on the three-dimensional finite element method, considering the climate characteristics in high-altitude regions and the limitation of conventional temperature control and crack prevention measures. The results show that the conventional pouring temperature control measures, water cooling measures, and surface insulation measures are unable to control the temperature stress of concrete within the safe range. The reasonable block-divided pouring measures (to avoid long pouring interval), reasonable post-pouring belt measures, and strong heat preservation measures are crucial to effectively control the thermal stress and ensure the structural safety. Based on the research and practice of concrete crack prevention in hydropower stations, during construction in high-altitude regions, the temperature and spatial distribution of concrete temperature stress, and a set of comprehensive crack prevention measures suitable for high-altitude climate conditions, construction conditions and structural characteristics of powerhouse are summarized and have reference significance for similar projects.

Qiaorong Sun, Bingyong Ding, Zaixin Zheng, Running Du, Sheng Qiang
Study on Variability of Mechanical Properties of Steel Rebars

Steel rebars are widely used in construction as reinforcement in reinforced concrete elements and for prestressing applications. The actual mechanical properties of steel bars might deviate from the specified values for a number of reasons. This deviation in mechanical properties increases the effect of material strength variability on the uncertainty associated with structural design. In this study, a statistical approach is undertaken for the variability analysis of Grade 60 steel rebars using 200 test data of different bar sizes. Beta and normal are employed to represent the variation in the in the yield strength, ultimate strength, bar diameter, and elongation. The Kolmogorov–Smirnov and Anderson darling goodness-of-fit test is carried out to identify the most suitable distribution for the considered properties.

B. Huda Sumaiya, Sisay Tadele, Saif Aldabagh, M. Shahria Alam

Materials Specialty: Alkali-Silica Reaction and Alkali-Activated Concrete

The Use of Self-Healing Technology to Mitigate the Alkali–Silica Reaction Distress in Concrete

Alkali–Silica Reaction (ASR) is one of the most harmful distress mechanisms affecting the durability and serviceability of concrete infrastructure worldwide. ASR-induced deterioration leads to micro-cracking, loss of material integrity and functionality, significantly impacting the stiffness, tensile, shear, and compressive strength of affected concrete. Over the past decades, studies have demonstrated that the partial replacement of Portland cement by supplementary cementing materials or the addition of lithium-based admixtures (e.g., lithium nitrate, etc.) is effective preventive measures against ASR. Yet, new studies are now finding that the deterioration is only delayed and not entirely prevented. In this context, it has been verified that some products, such as crystalline admixtures, could enhance concrete's healing properties, thus presenting an interesting solution to reduce water ingress and recover damaged concrete elements. However, the potential of these materials to suppress durability-related distress due to ASR has not been assessed. This paper aims to evaluate different concrete mixes presenting two different types/nature of highly reactive aggregates (i.e., coarse vs. fine aggregates), incorporating a GU-type cement, lithium nitrate, a hydrophilic crystalline waterproofing material (CW), and two modified versions (CW-mod). The samples were fabricated, exposed to ASR development, and monitored over two years. Mechanical (i.e., compressive and shear strength, modulus of elasticity, and stiffness damage test) and microscopic (i.e., Damage Rating Index) techniques were selected to further analyze the distinct mixtures’ appraised performance. The results show that the addition of CWs’ agents in concrete minimized ASR development. In general, the mixtures not only delayed the development of inner damage but significantly lowered the compressive strength loss and slowed the crack propagation in the cement paste at equivalent expansion amplitudes than control specimens. Finally, comparisons among the results found are made, and further discussions and recommendations on the reliability of adopting self-healing products to suppress ASR are conducted.

De Souza, Diego Jesus, Leandro Sanchez, Alireza Biparva
Alkali-Activated Concrete Workability and Effect of Various Admixtures: A Review

Alkali-activated concrete (AAC) is getting popular as a sustainable alternative for ordinary Portland cement concrete. Hence, questions regarding potential adaptation for existing concrete technologies to deal with performance issues of the new concrete type were raised. On top of these technologies, the efficiency of various admixtures and their interactions with the AAC's ingredients, hydration products, and microstructure development represent a knowledge gap. This paper reviews the workability requirements for AAC and the efficiency of various admixtures to achieve the targeted performance. The stability of admixtures in the alkaline medium, optimum dosages, and interaction with the activation process was highlighted. The reported data are anticipated to guide engineers in selecting suitable admixtures to achieve the desired workability while maintaining adequate performance.

Nourhan Elsayed, Ahmed Soliman
Utilizing Alkali-Activated Materials for Repair Applications: A Review

Alkali-activated materials are gaining attention as an alternative to cement-based materials. The high early strength and higher durability performance had promoted its use as a repair material for several structures. This review paper highlights the successful repair applications of alkali-activated materials. The selection criteria for the alkali-activated material mixtures meeting repair requirements are reviewed. The performance of the repaired elements, including mechanical and durability, is reviewed, highlighting the role of various alkali-activated materials properties. Based on the reviewed cases, recommendations for the utilization process for alkali-activated materials will be provided.

Ahmed Khaled, Ahmed Soliman
Evaluating the Performance of Phase Change Materials in Alkali-Activated Materials

The high energy consumption for buildings pursues researchers to examine various potentials to improve energy efficiency for construction materials. Among various potentials, the use of phase change materials (PCMs) demonstrated a high ability to modulate the inside temperature of the buildings. These materials can absorb and release the heat in a specific temperature range regulating thermal performance for mortars and concrete. However, the performance of PCMs, including stability and heat storage efficiency in non-cementitious mixtures such as alkali-activated materials (AAMs), is still questionable. Hence, this study evaluates the performance of micro-encapsulated paraffin, as an organic phase change material, in alkali-activated materials through various tests. Results showed that the high alkalinity of the used alkali activator did not significantly affect the performance and the stability of the micro-encapsulated PCMs. A slight reduction in the mechanical performance of the alkali-activated materials due to the addition of PCMs compared to cement-based mixtures was reported. This study can help the in situ engineers choose the proper mixture for environmental and mechanical performance.

Farshad Meftahi, Ahmed Soliman
Mechanical and Durability Properties of Alkali Activated Concrete Incorporating Recycled Aggregates

Buildings made of concrete have been proven to be safe and durable. Concerns over global warming and carbon emissions have grown in recent years. The construction sector, particularly cement manufacturing, accounts for a significant portion of worldwide CO2 emissions. Cement manufacturing is said to be responsible for 5–8 per cent of global CO2 emissions. It is observed that alkali activated concrete has good strength and chemical resistance. As we know that aggregates occupy 60–75% of the volume in concrete, so to overcome this problem, recycled aggregate can be used by improving its essential properties. Recycled aggregates are produced from processing previously used building materials such as construction and demolition of building waste. This study was undertaken to compare M30 grade alkali activated concrete (AAC) and ordinary concrete (OC). Exploratory experiments were conducted incorporating recycled aggregate (RA) to replace coarse aggregate with 10, 20, 30, and 40% in concrete. Mechanical properties including compressive strength, split tensile strength, flexural strength, modulus for elasticity, and durability properties such as sulphate attack, chloride attack, water impermeability, and RCPT after 28 days of curing has been compared. Mechanical properties of both concrete decrease as the proportion of recycled aggregate increases. Comparison of AAC and OC shows that at 40% replacement of natural aggregate with RA, there is marginal change in compressive strength at 28 days. However there is sharp decrease in flexural strength, in AAC compared to OC at all levels of replacement. Decrease in split tensile strength and modulus of elasticity is not more when OC and AAC are compared. AAC offers poor durability, such as high water absorption because of more voids present in it, surface cracking, and high chloride penetration compared to OC when incorporated with RA. Hence AAC with RA can be used for non-structural work like paver blocks or road furniture which is not subjected to aggressive environments but can be produced on mass scale. As AAC utilises industrial waste it is environment friendly and also less costly compared to OC.

Bhavya Patel, Sonal Thakkar, Urmil Dave

Materials Specialty: Recycled Materials

Developing Predictive Equations for the Self-Centering Response of Beam-Column Connections with Steel Angles and Shape Memory Alloy Bolts

This paper presents the development of predictive equations for the self-centering response of moment-resisting connections equipped with Shape Memory Alloy (SMA) bolts and steel angles. First, three-dimensional finite element models are developed in ANSYS. The analysis is validated using experimental results for seven beam-column connections. Using a design of experiments approach, a statistical sensitivity analysis of the cyclic response is performed to identify factors with significant effects. Next, a response surface study is presented to develop predictive equations for characterizing the cyclic response of steel beam-column connections with SMA bolts and steel angles. A confirmation study indicates acceptable accuracy of the developed equations for predicting the cyclic response of the SMA-based connections. The predictive equations can be used for developing computationally efficient models in the analysis and design of SMA-based connections and moment frames. This study also highlights the promising self-centering response of the newly developed SMA-based connections. Based on the results, deep beams should not be used to avoid possible early bolt fracture.

Saber Moradi, Majid Mohammadi Nia
Interpretable Ensemble Machine Learning Models for Shear Strength Prediction of Reinforced Concrete Beams Externally Bonded with FRP

Shear strengthening is a complex phenomenon that garnered significant attention in the structural engineering community. Due to the catastrophic nature of shear failures, several attempts have been made in retrofitting reinforced concrete (RC) beams out of which the incorporation of externally bonded fiber reinforced polymer (FRP) layers offer a remarkably fast, economical, and reliable solution. This paper presents an approach to predict the shear capacity of FRP strengthened RC T-beams using interpretable ensemble machine learning models. The study covers a comprehensive databank comprising a wide array of parameters including concrete design, FRP composition as well as beam cross sections. The efficiency of the developed models in predicting the shear capacity of FRP retrofitted RC T-beams is evaluated by comparing the results with several design guidelines. It is observed that the random forest and CatBoost models provide the most precise shear capacity estimations of the FRP retrofitted RC T-beams. The R2 and MAE values obtained from the random forest model were 0.897 and 0.128 kN, respectively, whereas those by the CatBoost model were 0.899 and 0.127 kN, respectively. The best performing model CatBoost is made interpretable using the Shapley Additive exPlanations which reveal that the most important input parameter contributing to shear capacity of the FRP strengthened RC T-beams is the height of the FRP layers used in the retrofit process. The proposed ensemble models presented in this paper are proved to be superior to the existing mechanics-driven models currently being used for design practices.

Jesika Rahman, A. H. M. Muntasir Billah
Evaluation of Concrete Characteristics Using Smart Machine Learning Techniques—A Review

Concrete is one of the most commonly used materials for a wide range of construction across the world. The heterogeneity of concrete results in wide variation in its properties. How different ingredients are mixed, determines the performance of concrete, especially its compressive strength. Hence, rigorous testing of concrete in the laboratories before it is finally selected to be used for a specific type of construction is required. This process of testing requires large quantities of material, time and money. The advent of machine learning and artificial intelligence appears to be promising and significant work has been done in this field for the development of high-performance concrete. Traditional curve fitting models provide the ability to interpolate data, however, this paper evaluates the efficacy of machine learning models and different types of neural networks that have been specifically utilized to predict in terms of various factors, the compressive strength of concrete. Various algorithms like group method of data handling (GMDH) type neural networks, adaptive neuro-fuzzy inference system (ANFIS), hybrid modified firefly algorithm with artificial neural networks (MFA-ANN) and other hybrid ANN algorithms have been used to perform a comparatively analyzed review.

Chinmay Kapoor, Navneet Kaur Popli, Ashutosh Sharma, Rishi Gupta
On a Universal Failure Criterion for Brittle Materials

To date, there is no universally accepted comprehensive explanation of brittle fracture in compressive stress fields. Researchers have developed many theories for brittle fracture, each of which is only applicable to particular materials and stress states. Additionally, some of these theories are based on questionable assumptions. A generalized fracture-based criterion should rationally explain brittle material behaviour across all stress states, providing unity in a poorly understood field. Visible crack formation implies the existence of tension to separate the surfaces. In the literature, there is no consensus on the source of these tensile stresses in compressive stress fields. Various sources of tensile stresses in compression are surveyed, with voids being found to be the most critical. Having identified the key source of tension, a way of predicting crack propagation is sought. Previously unsuccessful treatments of void-induced compressive fracture are examined, then a highly simplified way of quantifying the stress intensity factor (KI) in compressive fracture is proposed. The simplification is validated against numerically calculated KI values for circular and rhomboidal voids of different sizes. In addition to the numerical efficiency of the simplified calculation, the simplification defines a function $$\sigma \left( a \right)$$ σ a which can be used to explain and predict various compressive fracture phenomena which are counter-intuitive from a typical Griffith-type explanation.

Ahmed Ahmed, George Iskander, Nigel Shrive
Proceedings of the Canadian Society of Civil Engineering Annual Conference 2022
herausgegeben von
Rishi Gupta
Min Sun
Svetlana Brzev
M. Shahria Alam
Kelvin Tsun Wai Ng
Jianbing Li
Ashraf El Damatty
Clark Lim
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