Proceedings of the 4th Congrès International de Géotechnique - Ouvrages -Structures

This paper presents a review of unbound recycled materials, specifically recycled asphalt pavement (RAP) and recycled concrete aggregate (RCA), as road base course for sustainable highway construction. A total of fifteen recycled materials were collected for characterization and testing from across the USA. Compaction characteristics and resilient moduli of these samples were determined and predictive equations were derived. Test sections were constructed using recycled materials in the granular base layers at the MnROAD test facility. Large-Scale Model Experiments (LSME) replicating field-scale conditions were also conducted and scalability of various scale modulus measurements was investigated. When compared to conventional base course, RAP and RCA experienced higher modulus. Discussion includes mechanical and durability characteristics, and leaching behavior. Sustainability evaluation of material alternatives in a project is described.

A series of static and seismic loading tests of reinforced concrete frame assemblies were conducted in 2010, 2012, 2013 and 2014 to identify the effects of slab for evaluation of seismic capacities of reinforced concrete buildings as part of national research projects for review of the technical standards on seismic design practices in Japan. Two-fifth or half scale seven specimens were tested representing three-dimensional reinforced concrete beam-yielding frames with floor slab. A special loading set-up was invented and used to simulate the boundary conditions of the medium-story frame so that the axial elongation of the beams would not be constrained by the reaction supports consisting of pin-fixed and pin-roller. It was generally found from the series of tests and analyses that the slab reinforcing bars were increasing almost uniformly through the whole slab width and was fully effective to the flexural strength of the beams at around one percent story drift. The observed and calculated beam strengths with the full width of slab was much higher than those with the effective slab reinforcing bars assumed in the current design practice.

A unified access to dynamics of structures is presented. It is based on the idea of a Cosserat continuum which can be three, two- or one-dimensional. In the three dimensional case we can capture scale effects relevant to failure and stress singularities. In the two- and one-dimensional cases we arrive at shell and rod theories derived under the same umbrella. The development of stable energy-momentum integration schemes is key to capture the dynamics for large simulation times. Examples are presented to underline the suggested methodology. The formulations can be extended to capture anisotropies of fibre reinforced materials as well as for coupled systems.

The potential for structural instability in metal structures has been known since the famous paper of Leonard Euler in 1744 on column buckling. The constant challenge has been the desire to turn the excellent research worldwide in the area into design rules and specifications such as the Eurocodes, American Specifications, Japanese, Chinese and Australian Standards. New methods of stability analysis and design such as the Direct Strength Method (DSM) in the AISI S100 Specification and the Australian/New Zealand Standard AS/NZS 4600 for Cold-Formed Steel Structures have unified stability design across a range of buckling modes such as local, distortional and overall (Euler) buckling. Further, Advanced Analysis methods (often called GMNAI) which use the Finite Element Method (FEM) are being standardized for routine design of structural systems. The paper reviews these new methods, and their incorporation in design standards and specifications.

Beam-column joints are commonly considered critic regions for RC frames subjected to earthquake. That is why assessing the beam-column joint capacity is an important topic, especially for structures constructed before the modern seismic design codes, or for buildings in post-seismic situations. Among the in-situ structural assessment methods, the vibrational testing is currently mentioned. The authors have developed an analytical method to assess the damage evolution of a structure in function of its dynamic characteristics. The method consists of two main steps and the first one necessitates a robust model which can reproduce the static behavior of the studied structure. For this purpose, the authors try and assess the relevancy of existing numerical models to choose the most relevant for the second step. This paper presents an assessment of the CDP (Concrete Damage Plasticity) model implemented in the Abaqus software. First, an experimental study on a RC beam-column frames is presented. Unloading-reloading cycles were performed during the tests and the displacement fields were recorded by using the image correlation technique. The experimental data are used to assess the relevancy of the CDP model, but these data can be useful also for the further studies to verify and improve the accuracy of the numerical or analytical models.

The shear connector is the most important part of a composite beam and promotes a composite action between a steel beam and concrete slab. This paper presents the experiment results of three large-scale composite beams with a newly puzzle shaped crestbond rib shear connector. The behavior of this shear connector was investigated and the results were correlated with those obtained from the push-out-test specimens. Four-point-bending load testing was carried out on steel-concrete composite beam models to consider the effects of the concrete strength, number of transverse rebars in the crestbond and the width of the concrete slab. The results of large scale experimental test include of: the deflection, ultimate load, strains of the concrete, steel beam and Perfobond connectors; the relative slip between the steel beam and the concrete slab at the end of the beams; and the relative failure mechanism. The results showed that the general behavior of a steel-concrete composite beam using Perfobond shear connectors was similar to that of a steel-concrete composite beam using conventional shear connectors such as head stud shear conector. The newly puzzle shaped crestbond shear connectors showed satisfactory performance, and could be considered for application in composite structures.

The Finite Strip Method (FSM) has been developed for pre-buckling and buckling analyses of thin-walled sections under localised loading for general end boundary conditions. The theory is included in the THIN-WALL-2 V2.0 program which has been developed at the University of Sydney using a MATLAB graphical interface, Visual Studio C++ computational engines and a FSM module. The paper describes the application of the THIN-WALL-2 V2.0 program in analysis of thin-walled sections under the four localised loading cases namely IOF (Interior one-flange loading), EOF (End one-flange loading), ITF (Interior two-flange loading) and ETF (End two-flange loading). A linear analysis is required for pre-buckling analysis to determine the pre-buckling modes and the membrane stresses of structural members subjected to localised loading. These stresses are then used in the buckling analysis to get the buckling load and the buckling modes of the structural members.

This study performed on composited beam using normal concrete joined cement-based strain-hardening composite (CSHC). The bending resistances of composited beams are provided with a new approach as follows: CSHC is placed in extreme compressive zone at top of simple beam whereas normal concrete is placed in the lower part of beam. The models and equations are suggested for various cases of steel reinforcing bar to useful predict bending resistance of beam. Also, an experimental program is conducted to generally evaluate bending resistance of the investigated beams. The moment capacity and stiffness of the composited beam are clearly improved with the increase of CSHC thickness.

This study has been motivated to evaluate the practicality of numerical simulation of impedance monitoring for bolt-loosening detection in steel column connection. In order to achieve the objective, the following approaches are implemented. Firstly, the theory of electro-mechanical (E/M) impedance responses and impedance-based damage monitoring method are outlined. Secondly, the feasibility of numerical simulation of impedance monitoring is verified for several pre-published experimental examples on steel beams, cracked aluminum beams, and aluminum round plates. Undamaged and damaged steel and aluminum beams are simulated to compare to experimental impedance responses. An aluminum round plate with PZT patch in center is simulated to investigate sensitive range of impedance responses. Finally, numerical simulation of the impedance-based damage monitoring is performed for a steel column connection in which connection bolts are damaged. From the numerical simulation test, the applicability of the impedance-based monitoring to the target steel column connection can be evaluated.

In this paper, crack propagation in concrete dams is investigated using the eXtended Finite Element Method (X-FEM). The implementation of the crack model is undertaken through the development of a sub-program coded for this study. In order to simulate crack propagation, two level set functions are developed to represent a moving interface. The discontinuity of displacement due to the crack is introduced by a generalized Heaviside function and the addition of the asymptotic fields near the crack tip in order to improve the accuracy in elastic fracture mechanics. A validation example is presented to demonstrate the analysis procedure and capacities of the model. The results obtained show that the proposed model enables an accurate calculation of the Stress Intensity Factors (SIFs) and performs well for predicting crack trajectories. Finally, this work is applied to analyze and predict the fracture response in concrete dams and to evaluate the dam safety against cracking.

Hybrid reinforced concrete steel (RCS) frames consisting of reinforced concrete (RC) column and steel (S) are used frequently in practice for mid-to-high-rise buildings. RCS frames possess several advantages from structural, economical and construction view point compare to either traditional RC or steel frames. One of the most important elements in RCS frames is the composite shear wall consisting of several steel sections encased in reinforced concrete. Regarding the RC walls reinforced by more than one steel profile, namely “Hybrid” wall, although number of researchers have focused on its various aspects, they are currently not covered by standards because they are neither reinforced concrete structures in the sense of Eurocode 2 (1992) or ACI-318 (2005) nor composite steel-concrete structures in the sense of Eurocode 4 (1994) or AISC-2010 (2010). An experimental study on the static behavior of hybrid walls with several embedded steel profiles subjected to combined shear and bending is presented. Six hybrid walls with different types of the structural steel-concrete connection and reinforcement detailing are tested. The specimens exhibited ductility behavior. The experimental results indicate that the load bearing capacity of the hybrid specimens considerably grows, as result of the encased steel profiles. The specimens with shear connectors (i.e. headed studs, stiffeners) were more ductile in terms of displacement ductility than the ones without connectors.

This paper presents preliminary results on the formulation of a damage-plasticity model and its applications for the failure analysis of cold-rolled high strength steels. The model is based on von Mises plastic theory combined with a damage criterion to capture both hardening and softening responses. The proposed constitutive model is calibrated against available experimental data and implemented into the ABAQUS finite element (FE) package for the failure analysis in a tensile test of cold-formed steel (CFS). Both the experimental overall response of the member and its fracture pattern can be predicted, showing the potentials of the model in structural applications. In addition, both advantages and disadvantages of the model are discussed with proposals for further improvements.

In this paper, we developed a finite strain multiplicative elasto-plasto-dynamic formulation for Euler-Bernoulli and Timoshenko-type beam. The relations are formulated in an inertial frame approach. The multiplicative decomposition of the deformation gradient and the logarithmic strain measure are used. The exponential map for material evolution equations, as well as the derivative forms is given. In an attempt to deliver a stable time integration scheme for this non-linear beams in the context of finite strain elasto-dynamics, we made use of the concept of the energy-momentum method recently developed by the authors for geometrically exact Euler-Bernoulli and Timoshenko-type elastic beams. One example of finite strain elasto-plastic beam deformation is presented.

This paper proposes a fuzzy finite element procedure for dynamic analysis of planar steel frame structures with fuzzy input parameters. The fixity factors of beam – column and column – base connections, loads, mass per unit volume and damping ratio are modeled as triangular fuzzy numbers. The Newmark-β numerical integration method is applied to determine the displacement of the linear dynamic equilibrium equation system. The α-level optimization using the Differential Evolution (DE) involving integrated finite element modeling is proposed to apply in the fuzzy structural dynamic analysis. The efficiency of proposed methodology is demonstrated through example problem relating to for the twenty-story, four-bay portal steel frame.

Geometric imperfections have a significant effect on both buckling and strength capacities of structural members. It is essential to accurately measure the geometric imperfections for finite element simulation especially for thin-walled sections. This paper presents the procedure to measure and incorporate geometric imperfections into finite element models using ABAQUS software package with the focus of attention for cold-rolled aluminium sections. Laser scanners are firstly used to measure geometric imperfections along high-precision tracks while recording the distances to corresponding points on the surface of specimen. The measurement lines are located around the cross-section. Subsequently, a MATLAB code is developed to incorporate the measured imperfection magnitudes into a perfect mesh of the finite element model. The Fourier series approximation is used in the longitudinal direction along measurement lines while the linear interpolation is used for flanges, lips and web in the transverse direction.

Fatigue of solder joints remains one of the critical concerns in thermo-mechanical reliability of high-power electronic systems. Several semi-empirical fatigue models based on effective material properties at macro-scale already exist, but have shown some limitations for providing accurate lifetime prediction of solder joints in the scale of microelectronic packages. Therefore, there is a need to enrich the existing approaches by a description of the failure mechanisms at the microstructure scale, taking into account some important features of the alloy. In this study, a 3D microstructure-informed model for reproducing the intergranular fatigue crack in the solder joint is developed. The submodeling technique has been applied in order to only investigate the critical zone of the solder joint. A global model of the whole module is first simulated to obtain the inputs for a submodel focused on the zone of interest where failure is expected to develop. The submodel simultaneously makes use of the cohesive zone and the crystal plasticity theories to represent decohesion at grain boundaries and plastic slips in the grains of the solder joint, respectively. Simulations of repeated thermo-mechanical loading on the package demonstrate how cracking occurs at grain boundaries in the solder joint of the submodel. In addition, it is shown that the crack propagation rate is almost constant during the whole loading time. This suggests an ability of the present approach to give a fatigue lifetime estimate for the entire solder joint by extrapolating some specific computed quantities from the local model.

The displacement of foundation due to the deformation of soil base has a significant effect on the internal forces and reactions resulted from an analysis of building structure. However, this effect is generally not properly considered, causing eventual large errors in structural analysis and design. In this work, the authors aim to model the interaction between a shallow foundation and soil base by using contact conditions to analyse the building structure which is simultaneously exerted by the external loading and deformation of soil base. The internal forces and reactions obtained with this analysis are compatible with the deformation of soil base—namely, the displacements of foundations are exactly the consolidated settlements of the soil base and the internal forces caused by the unequal settlement are also included in the results. Because of the nonlinearities of the contact conditions and the soil characteristics, the discrete equations resulted from the finite element discretization are nonlinear, which can be solved by Newton-Raphson scheme with the aid of tangent stiffness matrices.

The article presents the numerical study dealing with the behavior and the real load bearing capacity of hybrid walls by Abaqus software. Especially identify the bearing capacity behavior of the composite steel-concrete walls with several fully encased steel profiles (hybrid walls) while the materials were yielded until failure. Structural hybrid steel-concrete walls, material constitutive law for steel and concrete, load schematic, element types, numerical solution controls, interactions, steel-concrete bond, composite behavior and mechanical contact, … will be described in detail. It is expected that nonlinear FEM analysis can give more details on behavior as well as on shear and bending resistance mechanisms until failure of the hybrid walls. The nonlinear FEM analysis able to predict well specimen strength, maximum displacement, strains and stress distribution, crack pattern and failure modes. The reliability of this method was evaluated by comparing the analysis results with the experimental results.

The paper describes finite element analyses using the program ABAQUS 6.14 of cold-rolled alluminium alloy 5052 channel sections in stub column tests. Aluminium structural members have been used considerably in not only roof systems but also primary load-bearing components due to such advantages as superior corrosion resistance, light weight, ease of maintenance, constructability and recyclability. While the majority of aluminum structural applications are formed by extrusion, recently, aluminum Z- and C- sections have been successfully cold-formed from aluminium coil using existing rollers for cold-formed steel sections. The results of nonlinear analysis by the finite element method (FEM) depend on the measured input parameters such as the material properties, actual initial geometric imperfections and forming-induced residual stresses. The paper summaries the results of the finite element nonlinear simulations of the stub column tests on channel sections performed at the University of Sydney. The FEM results are compared and calibrated against the tests. The effect of the measured input parameters is also discussed thoroughly.

This work presents an analysis of the behaviour of composite steel-concrete columns under natural fires which include cooling phase. Thermo-mechanical numerical simulations based on the non-linear finite element method are conducted using the parametric fire model of Eurocodes to represent the natural fires. Results show that structural failure of the composite columns during or after the cooling phase of a fire is a possible event. The duration of heating phase (DHP) leading to the failure of structures during or after the cooling phase is always lower than the fire resistance of structures exposed to heating phase only. Parametric studies have been done to show the relationships between DHP and some major parameters such as load ratio, slenderness of column, eccentricity of load. This work enhances the understanding of the structural behaviour under natural fires.

Self-drilling screws have been used extensively in cold-formed steel structures. The American Specification and Australian Standard both provide design checks for different limit states of screwed connections. However, in a connection undergoing bending, while a screw may fail, other screws may be still in the elastic state. Therefore, investigation in the load-deflection response of screw connectors before failure is required for further understanding of complex screwed connections. This paper describes a shear test using 3 screws connecting in G450 steel sheets. A 3D finite element (FE) model was developed and validated using ABAQUS software. The simulation is able to reproduce the experiment’s results in term of shear strength, stiffness and ductility of the connections. The simplicity of this model allows it to be adapted into full scale connection modeling.

The current approaches authorized by Eurocode 2 for the design of reinforced concrete (RC) structures at the structural scale are: linear-elastic analysis, linear-elastic with limited redistribution of moments, plastic and non-linear analysis. Numerous experiments on RC beams were performed which provided interesting information for the models proposed in the standards. However, at the RC frame level where the beam-column are present, although several experiments have already been carried out in the literature, this topic is still to be investigated, due the important number of parameters: interior joint, exterior joint, stiffness ratio between beam and column, steel reinforcement type, … This paper presents firstly an experimental study on an H-form RC frame structure (two vertical columns and one horizontal beam). Several loading-unloading cycles were carried out. Displacement fields during the test were measured by the image correlation technique. Then, experimental results were compared with that of the analytical models proposed in Eurocode 2 and an advance FE code (CAST3M). The comparisons show that analytical methods presented in Eurocode 2 underestimated about 20–30% of the ultimate capacity of the structure; while the non-linear analysis with CASTEM code – when material characteristics and boundary conditions are correctly identified - could provide good results comparing to the experiments.

A newly puzzle shape of crestbond rib shear connector is a type of ductile perfobond rib shear connector. This shear connector has some advantages, including relatively easy rebar installation and cutting, as well as the higher shear resistance strength. Thus, this study proposed a newly puzzle shape of crestbond rib with a “ʊ” shape, and its shear resistance behaviors and shear strengths were examined using push-out tests. Five main parameters were considered in the push-out specimens to evaluate the effects of shear resistance parameters such as the dimensions of the crestbond rib, transverse rebars through the crestbond dowel, concrete strength, rebar strength, and dowel action on the shear strength. The shear loading test results were used to compare the changes in the shear behaviors, failure modes, and shear strengths. It was found that the concrete strength and number of transverse rebars in the crestbond rib were significantly related to its shear resistance.

This paper addresses the strength and deformation capacity of shear wall subjected to seismic loading using experiments and analysis. Two low-rise shear walls, with the same section design and the same aspect ratio (height/length) of 0.4 have been submitted to pseudo-dynamic (PSD) tests conducted at the ELSA laboratory of the Joint Research Centre are presented. Simulation of the behavior of the shear wall retrofitted by CFRP is accurately predicted by finite element modeling. The accuracy of modeling is confirmed by comparing the simulated response with experimental one.

In the previous papers, the steel pile ultimate strength and plastic deformation capacity for local buckling is estimated with radius thickness ratio and shear span ratio. For real structures, concrete is filled into the pile top of steel piles to fix the connection between a steel pile and a reinforced concrete footing beam in. It is considered that the local buckling strength of steel piles with concrete at the pile top is larger than that of steel piles to prevent local buckling issued from filled concrete at the pile head. On the other hand, at the pile top filled with concrete, bending stress of steel pipes is not enough transmitted to a concrete member which slips on the steel pipe. Therefore, slip stoppers are attached to the steel pile top. The stress transfer mechanism between a steel pipe with slip stoppers and a concrete member has not been clarified In this paper, cyclic load tests of steel piles filled with concrete at the pile top with different axial force ratio are performed. The local buckling behavior of steel piles at pile top is elucidated and ultimate strength, deformation capacity and hysteretic energy absorption is evaluated.

In seismic engineering, taking into account the non-linear behavior of the structure into the calculation of its responses against strong ground motions, which are due to plastic and/or damage, is not easy because of the need, in terms of computation time and memory, due to many iterations required at each step in order to satisfy the equilibrium. It is common that many concepts of equivalent linear behavior have been used in order to determine the maximal response of structure without performing non-linear transient calculation. In this paper, we deal with systematic and argumentative analysis in order to establish a concept of equivalent linearization by considering the equivalence criterion through the transfer function from the time domain to the frequency domain. Its idea is to identify the frequency and damping of the equivalent linear oscillator whose theoretical transfer function of response in acceleration fits the best the experimental one of the nonlinear system. This concept will be applied to elastoplastic Sdof oscillators undergoing the filtered white noise signal Clough-Penzien. As the result, this equivalent linearization reestablishes the transferred signal through a structure with the non-linearity.

Construction of cable stayed bridges is very challenging. These structures are extremely redundant and the effect of tensioning one cable has the effect of changing the stresses of the already installed cables. In order to achieve a targeted service state at the end of the construction process careful calculations has to be done by the contractor in order to ensure it. However, deviations arise between the modelling of the tensioning process and the actual results obtained on site. In order to adjust the final stresses in the cables, a final restress of the stays is unusually required. This re-stressing operation is usually done for the whole cable, as the strand by strand stressing technique used for the first stressing operations, cannot be used anymore. This last operation is costly, time consuming and has less accuracy, compared with the strand by strand tensioning techniques. The paper will present a method to control the tensioning process on site and to modify it according to the stresses measured in the cables at each stressing stage. In this way, the chances of requiring a restressing operation are diminished.

Cohesive zone models have been widely used for modelling failure of interfaces in laminated composites and also for representing the behavior of the Fracture Process Zone in modelling geomaterial failure. Despite their importance and usefulness, most existing models do not adequately take into account the underlying mechanisms of dissipation at a lower scale that include both micro-cracking and friction between micro-crack surfaces. These models either rely on a single scalar damage variable to represent the deterioration process, or inadequately account for the role of friction in governing the interface behavior and failure in mixed mode conditions. In this work, we use a thermodynamics-based formulation of a damage-plasticity cohesive model for the analysis of its behavior in relation to the variation of frictional contribution to the energy dissipation budget. The advantages of the proposed formulation in directly linking frictional contribution with the mechanical responses are highlighted.

Every year, a huge amount of waste materials containing toxic substances are produced throughout the world, which causes serious damage to the environment and poses threats to human health. Among available techniques of immobilization of toxic elements in harmful by-products is geopolymerization which has been considered as an effective approach to deal with many environmental issues. Apart from being utilised as alternatives for Portland cements in construction, geopolymer materials are also used as binders in waste solidification and stabilization systems . This study focuses on the potential application of geopolymeric systems in coping with hazardous wastes regarding the immobilization mechanism and factors influencing the immobilization efficiency, which provides a better understanding of the stabilization of pollutants through geopolymerization in order to stimulate further research on addressing the hazardous waste.

Strain-hardening high performance fiber-reinforced cementitious composites (HPFRCCs) are classified as a smart construction material with high damage-sensing capacity in addition to high structural resistances. The damage-sensing capacity has often been evaluated by measuring the changes in the electrical resistance during test loading. Thus, the electrical resistivity behavior of HPFRCCs is a key non-structural property that should be clearly understood to develop the self damage-sensor. In this study, the electrical resistivity behaviors of HPFRCCs were experimentally investigated with various HPFRCCs as follows: plain mortar, HPFRCCs with steel fibers, HPFRCCs with steel and carbon fibers, HPFRCCs with steel and multi-walled carbon nanotubes. The electrical resistivity properties of investigated HPFRCCs were compared and discussed.

Earth is an ancient building material which has been recently the focus of scientific research due to its sustainable properties. The disadvantage of earthen material is its low strength and its sensibility to the water content. To enhance the durability and the mechanical characteristics of earthen material, hydraulic binders are currently added (cement or lime) which have high embodied energy and therefore increase the embodied energy of the stabilized earth material. This paper presents an exploratory study which uses geopolymer as a stabilizer for earthen material. Geopolymers are inorganic binders with polymeric structure obtained by alkaline activation of raw materials containing silicon and aluminum; they are obtained by dissolution/precipitation reactions at low temperature. The present study proposes to use blast furnace slag as geopolymer raw material, which was mixed with an alkaline solution activator to obtain the stabilizer for earthen material. The geopolymer effects were investigated on two types of earthen material: rammed-earth (RE, soil dynamically compacted) and soil-geopolymer-concrete (soil poured with more water content). The results show that geopolymer had more effects in soil-concrete than in rammed-earth. Indeed, RE specimens stabilized by geopolymer did not present a significant improvement of compressive strength comparing to the unstabilized RE specimens. Soil-geopolymer-concrete specimens had double compressive strength comparing to soil-cement-concrete specimens.

Quarrying cause pollution and environmental destruction, natural resources dwindling, while sand mining could cause the river erosion, change in flow, and ecological imbalance. Besides, steel slag is scrap produced along with the development of the iron industry. This waste without proper treatment will affect the environment. The utilization of steel slag as raw material replaced crushed rock in concrete production is a study topic in order to reduce environmental pollution caused by steel slag. The behaviors of reinforcement in a reinforced concrete beam using steel slag replacing crushed-stone aggregate, which is called as SRCB, are explored in the article. It is presented in comparison with reinforcement in crushed-stone aggregate concretes (RCB).

Pumbability of freshly-mixed concrete is a great challenge in the construction field; this attracts a growing number of researchers willing to study. This study pays attention on the use of empirical models that are established from the experimental data to evaluate the concrete pumpability. The purpose of the study is to reduce the amount of cost and time involved in the project construction. The models permit to directly estimate interface parameters (i.e., the viscous constant (η) and the interface yield stress (τ_0t)) from the concrete formulation. These parameters directly affect the interface friction (τ) between the concrete and the wall of the pumping pipe, and thus the concrete-mix mobility (i.e., the pumping flow rate) can be improved by reducing the interface friction. The calculated interface parameters are then validated with measurement parameters using a tribometer. In this study, a parametric approach is also employed by varying formulation parameters such as water/cement ratio, cement paste volume, and aggregates/sand ratio of the concrete-mix. The obtained results demonstrates that the empirical model is reliable with a high precision. They permit to validate a theoretical approach to estimate and to optimize the pumping parameters and the concrete pumpability.

This paper experimentally investigates the behavior of concrete filled fiber reinforced polymer (FRP) cylinders under cyclic axial compression. The FRP used in this study were either Glass FRP or hybrid Large Rupture Strain (LRS-FRP) and conventional Glass FRP (GFRP). LRS-FRP are manufactured out of polyethylene naphthalate (PEN) and polyethylene terephthalate (PET) obtained from recycled plastics. Hence, they are much cheaper and environment-friendly than conventional GFRP or carbon FRP (CFRP). LRS-FRP has high tensile rupture strain (usually greater than 5%) compared to 1-2% for GFRP and CFRP. This study presents the results of a total of 5 specimens having different confinement ratios to investigate the behavior of concrete filled LRS-FRP or hybrid LRS-FRP and GFRP tubes in terms of ductility, ultimate strain, and strength improvement. The results showed that using LRS-FRP significantly improved the ductility of the confined concrete. However, the improvement in strength was limited. The hybrid confinement improves both the ductility and strength.

The using of silica fume replaces a part of cement in concrete production leading to the cement hydration mechanism in binder paste has changed. The hydration of cement and the accompanying phenomena such as heat generation, chemical shrinkage development are the results of interrelated chemical processes. Therefore, the chemical composition in pure cement directly affect to a specific concrete mixture.The Reactive Powder Concrete (RPC) is Ultra-High Performance Concrete (UHPC). It is composed of the small aggregates and the ultrafine such as the silica fume (SF) for reaching a high compact. The high compact and the using less water in concrete can lead up to the high durability as well as ultra-high strength in the material concrete. The high durability and ultra-high strength of concrete with the using of silica fume for concrete production contributes to reduce environmental pollution.In this paper, the characteristics of the development of chemical shrinkage from 2 days to 7 days in RPCs are analyzed. These RPCs are made from three different types of cement with different content of of mineral components in its. The analysis focuses on the characteristics of the hydration pore (as well as the chemical shrinkage) formation in concrete by time when the content of minerals composition in the cement changes.The hydration pore model is calculated basing on the simulation program for microstructure development of cement-SF paste in the process of cement hydration. The program of the hydration is verified via measuring heat flux emitted from hydration process by isothermal calorimetry for all concrete samples containing different types of cement. As parallel, the development of the hydration pore (as well as the chemical shrinkage) is determined by experiment on measuring by gravimetry for these RPCs.

In this study, we aim to shift attention to ability of chloride binding of supersulfated cement and its use for formulating sea water/sand mixing concrete. To formulate SSC cement, slag as main component is activated by high alkaline of C-H and the following reaction with SO₄2−. Material analysis (XRD, SEM/EDX) showed that effectively low-Ca-ettringite products were formed abundantly at early age and others chloride binding products such as Friedel’s salt, hydrotalcite in their turn were resulted at later age in high Cl− solution. Notable high ratios of bound Cl− on total Cl− indicate eventually capacity of hydrated cement matrix in neutralizing chloride content in seawater. As an addition, very low Cl− permeability of mortar specimen could be taken into account. By monitoring the corrosive state of embedded steel bar ϕ8 mm (inside mortar prism 40 × 40 × 160 mm, with seawater exposure condition), we observe no major deterioration due to such natural anti-corrosion phenomenon.

Unbound base course performance is highly dependent to resilient modulus and permanent deformation of unbound layers. Plastic strains are affected by the number of traffic loading. A Large Scale Model Experiment (LSME) test was conducted on unbound granular materials for 10,000 load repetitions and different thicknesses to determine the relationship between resilient modulus and plastic deformations. The results show that this relation is linear and can be explained by a progressive accumulation of the plastic deformations, reducing the voids and increasing the rigidity of the material. This proves that, in situ, the modulus varies with the repetition of traffic and this behavior is important for predicting the modulus for pavement rehabilitation. The moduli do not show large variations with the number of load cycles but increase with the thickness of the base layer. Plastic deformation decreases with increasing modulus of the material and the modulus itself increases with the thickness of the layer. Between 20 cm and 30 cm, permanent deformation decreases slightly, but the modulus after 10,000 cycles increases about 35%. To predict the plastic strain of unbound layers under repetitive loading, regression models are proposed.

This paper presents correlations between penetration index measured from dynamic cone penetrometer (DCP) and properties of pavement layer materials. A series of DCP tests were conducted both in the laboratory and in the field. The DCP data were analyzed and interpreted to generate a representative value of penetration per blow or DCP penetration index (DPI) for the material being tested at a given test condition. Basic properties of pavement layer materials e.g. crushed rock base, soil-aggregate subbase, sand embankment, natural subgrade etc. were tested and reported herein. By achieving appropriate moisture content and compaction quality, the empirical relationships between DPIs and properties of pavement layer materials from different test conditions indicated reasonable trends and thus confirmed its potential adoption for routine pavement layer evaluation in Thailand.

The U.S. companies need to mine billions of tons of raw natural aggregates each year. In the same time, billions of scrap tires are going to landfills every year which makes the replacement of using natural aggregate with recycled and sustainable one is more beneficial to both industry and environment. This paper presents an extensive study on the performance of the chip seal pavement surfaces in terms of aggregate retention and performance. This study introduces a new eco-friendly chip seal by implementing the crumb rubber made of recycled tires as aggregates for such surface dressing. Twenty four specimens of chip seal were prepared and tested under three tests investigating the aggregate retention. The tests included the standard Vialit test, modified Vialit test, and sand patch test. Two types of emulsions, two types of binders, and three types of aggregates including the crumb rubber were examined in the tested specimens. This study revealed that the crumb rubbers from recycled tires would be used in the chip seal as aggregates but it is preferable to be used in conjunction with the conventional aggregates. The crumb rubber showed a remarkable performance in aggregate retention. This performance was mainly because of the low weight of the crumb rubber and its rough surface, which increased holding the crumb rubber into the asphalt emulsion or binder. In addition, crumb rubber as a partial or total replacement for the mineral aggregate was successfully implemented in the field using the traditional procedure and equipment.

The coal bottom ash is a solid waste generated from coal-fired thermal power plants that contains high alumino-silicates resources. Rice husk ash was burned from rice husk which has over 80% silica in its chemical composition. The alumino silicates resources in these materials have high reactivity in various conditions such as that of alkaline reactions and thermal reactions. Therefore, both coal bottom ash (CBA) and rice husk ash (RHA) are promising raw materials for synthesizing alkali activated materials through geopolymerization. This study focuses on utilization of CBA and RHA to produce geopolymer – based materials using sodium silicate solution as an alkali activator. This is one of the potential solutions that would not only manage the coal bottom ash but also an avenue to utilize the waste to produce green materials. The production of geopolymer-based materials results to lower energy consumption, minimal CO₂ emissions and lower production cost as it valorizes industrial waste. The CBA and RHA were mixed with sodium silicate solution to obtain the geopolymeric pastes. The pastes were molded in 5-cm cube molds according to ASTM C109/C109 M 99, and then cured at room temperature for 28 days. The 28-day geopolymer specimens were tested for engineering properties such as compressive strength (MPa), volumetric weight (kg/m3), water absorption (kg/m3) and thermal conductivity (W/m.K). Microstructure of the best geopolymer sample was characterized by using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscope (SEM).

“Tsubasa PileTM” developed by JFE Steel is a Rotary penetration steel pipe pile with toe wing, Toe wing is formed by installing two semicircular steel plates in a crosswise position to each other at the end of the steel pipe pile. “Tsubasa PileTM” has been increasingly used in various fields by taking advantage of large bearing capacities and environmentally-friendliness such as driving without removing any soil, low noise and non-use of cement milk. In addition, JFE Steel is developing new technologies including the use of batter piles.

Fiber reinforced polymer (FRP), as a new alternative construction material compared to conventional materials like concrete and steel, has been introduced into civil infrastructure area for centuries and gained increasing interests by many researchers and contractors. FRP exbits several property advantages, such as high strength-to-mass ratio, ease of handling, and relatively high resistance to corrosion. However, one problem that hinders this material from wider acception in civil infrastructure application is the durability of FRP subjected to harsh complicated environmental conditions has not been fully investigated yet. This paper is aim to study the performance of the polyester-based glass fiber reinforced polymer (GFRP) subjected to combined cement alkaline solution, freeze-thaw cycles, wet-dry cycles, heating-cooling cycles, and sustained mechnical load. Concrete was poured into GFRP tube to make concrete-filled FRP tube (CFFT) cylinders, and the cylinders were put into environmental chamber with sustained axial load on. The concrete core of the CFFT cylinders was removed after 72-day’s conditioning, and the outer GFRP tube was cut into ring specimens to conduct hoop tensile tests. Test results indicated that the conditioned GFRP was slightly degraded in strength, but had significant decrease in strain. Sustained load had negligible effect on the strength of GFRP specimens, but did further deteriorate the strain of loaded specimens compared to unloaded specimens.

The use of cold-formed steel structures in the construction industry has become widely popular over the past decade. This has led to the necessary understanding of the effects of cold-working process on cold-formed steel members. The manufacturing process of cold-formed steels starts with cold-rolling the hot-rolled steel sheet under a series of rollers until a thickness is achieved. The process is followed by cold-bending to create cold-formed sections with desired shapes at ambient temperature. The plastic deformation associated with the rolling and bending processes results in strain hardening of the material and this in turn affects the properties. This paper presents both microstructural and micromechanical investigations on the blank and bent areas of 3.0 mm thick C-shaped cold-formed sections. Vickers hardness tests show a hardness increase at the bent areas. The observation of the bent region using scanning electron microscopy (SEM) reveals changes in the grain structures. Additionally, electron backscatter diffraction (EBSD) measurements have been conducted for an in-depth characterization. Understanding the changes in the microstructure of the material will provide insight on the mechanical behavior of these members.

This article presents experimental study to analyse the effect of pre-compressive loading on the chloride permeability of concrete used in anti-permeable admixture; the admixture was mixed in concrete with compression resistance of 30 MPa for casting specimens. Specimens was pre-compressive loaded at different stress levels including values in elastic phase and in diffused damage phase. After reloading, specimens were treated and put into measurement cell for chloride permeability evaluation. The results show significant effect of pre-compressive stress on chloride permeability of concrete, especially when damage appeared. effect of anti-permeable admixture on concrete permeability was also clarified.

The objective of this study was to evaluate the effect of artificial aggressive conditions on durability of reinforced concrete (RC) columns wrapped with CFRP. Three groups of RC columns (150 × 300 mm) were casted and cured in same condition. They were, subsequently, exposed to three accelerated corrosion conditions, wrapped with one CFRP sheet, and then subjected to further post-repair corrosion. Artificial aggressive conditions were created by using mixed chloride and sulfate solutions, environmental cycling and temperature - humidity chamber. Initially, CFRP sheet worked as a protection barrier. It prevented aggressive agents (Cl− and $$ {\text{SO}}_{4}^{ - } $$SO4-) from penetrating into concrete layer and declined possibility of corrosion of reinforcing steel. Nevertheless, anti-corrosion performance of CFRP sheet decreased sharply under the impact of high thermal condition. Eventually, the results revealed the anti-corrosion performance of CFRP-wrapped RC columns depend on the remaining content of harmful factors in concrete layer before being wrapped.

Expansive soil poses plenteous problems to the structures placed over it, such as, road pavements, buildings and canals, etc., mainly because of high swell index induced by its high-water retention capacity. Flexible pavements with expansive soil as a subgrade material are characterized with meager performance mainly due to cracking and differential settlement. The current study engages with the cost effectiveness of treated expansive soil as subgrade material. Lime and stone dust have been blended with soil at varied percentages to enhance the suitability of this mix as subgrade material. To catch on the extent of influence of stabilizing mixture, Modified Proctor and California Bearing Ratio tests have been performed on treated soil. The thickness of various layers of pavement has then been evaluated in conformity with IRC: 37 [1] and then cost analysis has been made for pavements with both untreated and treated subgrade course. It has been discerned that when expansive soil is stabilized with lime-stone dust mix (5–12% by weight of mix), the drop in the cost of flexible pavement is found to be maximum, i.e., 6.55% of cost reduction can be achieved if the pavement subgrade section is made up of treated soil instead of untreated one.

Textile reinforced concrete (TRC), a new generation of cementitious material, is used for different applications in civil engineering. The aim of this paper is to propose a methodology to identify the thermo-mechanical behaviour of the TRC material. The studied TRC composite is made with a cementitious matrix and grid alkali-resistant glass textile. In this study, TRC specimens are subjected to two types of thermomechanical test designated by the loading path 1 and the loading path 2. The results of the thermo-mechanical tests are discussed. This study presents also an experimental methodology, using the digital image correlation (DIC) technique, which permits to identify the specific cracking mode, the crack width and the distance between the cracks of the preheated-cooled TRC specimens as a function of the uniaxial monotonic axial stress. The experimental study is then followed by an analytical model that aims to calibrate existing analytical models (Gibson and Bisby models) for the prediction of the evolution of properties (ultimate stress and post-cracked stiffness) of the TRC material as a function of the temperature.

Among two common forms of CFRP used in strengthening/repairing construction structures (pultruded and hand-made), hand-made CFRP is popularly used with column and other structures where the strengthening surfaces are complicated. Normally, the hand-made CFRP (H-CFRP) includes woven carbon fibers, prefabricated in the factory and the polymer matrix which is added during the installation process. When a fire happens, structures and reinforced material are simultaneously exposed to high temperatures (up to 1200 °C) and mechanical loadings, which are complicated and difficult to be experimentally simulated. As far as the authors concern, the studies of CFRP and structure reinforced with CFRP in fire are rare due to expensive cost of experiments and insufficient theoretical calculations. For these reasons, this study aims to investigate the thermo-mechanical behavior of H-CFRP via two different elevated-temperature and mechanical load regimes. The first regime studies the ultimate-strength evolution as the exposed temperature increases while the second studies the variation of rupture temperature when applied load changes. The results from the first regime show that the ultimate strength and the Young modulus of H-CFRP generally reduce 50% and 25% when the applied temperature level increases from 20 °C to 400 °C. The second series show that the rupture temperature of H-CFRP steadily reduces from about 640 °C to about 467 °C as its mechanical stress ratio increases from 0.1 to 0.5 (of its ultimate strength at 20 °C). Remarkably when the mechanical stress ratio of H-CFRP increases to 0.75, the rupture temperature dramatically drops to about 50 °C. The rupture modes and correlation between two regimes will also be discussed.

This paper reports the influence of high calcium content in alkali-activated fly ash (AAFA) paste mixtures on the compressive strength, setting time, and workability. Class C fly ash was used to prepare alkali-activated paste mixtures. Four different sodium silicate to sodium hydroxide ratios of 2.5, 1.5, 1.0, and 0.5 were used as alkaline activators with a constant sodium hydroxide concentration of 10 M. Two curing regimes were also applied, oven curing at (70 °C) for 24 h, and ambient temperature at (23 ± 2 °C). The delay time between mixing and starting curing the specimens in the oven regime is 2 h. The compressive strength of the specimens was tested at 7 days for both curing regimes. The results showed that the fresh AAFA pastes had shorter setting time and lower workability with increasing the ratio of alkaline activators to fly ash ratio. However, the compressive strength of hardened AAFA was increased when the ratio of alkaline activators to fly ash ratio increased. A water to fly ash ratio of 0.3 with alkaline activators to fly ash ratio of 0.25, which displayed a balance between the fresh and hardened AAFA properties. The optimum sodium silicate to sodium hydroxide ratios were 1.0 for ambient curing and 1.5 for oven curing. The compressive strength of AAFA has reached up to 8 ksi after 7 days for ambient curing and 10 ksi for oven curing with initial setting time of approximately 180 min.

This study focuses on manufacturing bio-insulation fiberboards from bamboo fibers and bone glue, modified with sodium lignosulfonate. The microstructure of these boards is investigated by mercury intrusion porosimetry. The porosity and average pore size of boards are decreased; however, the specific pore surface is increased with the presence of bio-glues in boards. The hygric properties are examined through kinetics of water vapor sorption at equilibrium states. The thermal conductivity and bending properties are also studied. The thermal conductivity is dependent on relative humidity levels and moisture content of the fiberboards. The bending property is increased with 30% (w/w) of mixture glue between bone and sodium lignosulfonate in boards.

In this paper, we present studies in laboratory where we used bauxite Tan Rai and synthetic gypsum DAP Dinh Vu to fabricate cement clinker of calcium sulfoaluminate. Results of compositional analysis by XRD revealed major phases of ye’elimite 4CaO.3Al₂O₃.SO₃ (C₄A₃Š), belite 2CaO.SiO₂ (C₂S), anhydrite CaO.SO₃ (CŠ) in the sintered product. With the aim of combining two hydration mechanisms of CSA cement (rapid) and slag cement (slow), we then formulated blended cement from mixture of 15.58%wt CSA clinker and 73.36%wt fine ground granulated blast furnace slag and 11.06%wt synthetic gypsum. Specification tests of prepared cement were conducted conforming to the requirement of standard BS EN 15743 for supersulfated cement. In term of strength development, we noted quite high strength gain after 7 days in both tap water and sea water mixing cement. The global compressive strength of cement mortar met the grade 40 MPa of standard. Considering its practical application, we discuss on the perspective using this special cement for concrete under severe condition after taking into account further study on durability.

Hemp concrete is a non-loadbearing material used as filling material to form the building envelope. Hemp concrete is an hygroscopic bio-material characterized by a strong hysteretic hydric behavior and interesting thermal conductivity. A numerical tool able to model the hysteretic behavior of the hemp concrete sorption process is presented. The implementation of a suited hysteresis model in a heat and moisture transfer model allow evaluating and discussing the influence of this phenomenon in the transient hygrothermal response of hemp concrete to hydric loadings. The governing system of strongly coupled unsteady differential equations is implemented in Matlab with a finite differences method. Numerical transient hygrothermal responses of hemp concrete submitted to cyclic hydric isothermal loadings are then produced and compared with experimental results.

This paper experimentally investigates the seismic behavior of a large-scale, hollow-core, fiber-reinforced, polymer-concrete-steel HC-FCS column under cyclic loading. The typical precast HC-FCS member consists of a concrete wall sandwiched between an outer fiber-reinforced polymer (FRP) tube and an inner steel tube. The FRP tube provides continuous confinement for the concrete wall, along the height of the column. The column is inserted into the footing and temporarily supported; then, the footing is cast in place around the column. The seismic performance of the precast HC-FCS columns was assessed and compared with previous experimental work. The compared column had the same geometric properties; but the steel tube was 25% thicker than the column that was tested in this study. This paper revealed that these HC-FCS column assemblies were deemed satisfactory by developing the whole performance of such columns and using that performance to provide excellent ductility with inelastic deformation capacity by alleviating the damage at high lateral drifts.

Semi-flexible material is a composite pavement surfacing that uses both asphalt concrete (AC) with a unique structure and Portland cement concrete (PCC) in the same layers. The AC introduced in this kind of pavement is initially designed with the air-void content in the range of 25–35%, while the grout of Portland cement is the mixture of Portland cement, silica fume, silica sand, water and a suitable amount of plasticity additive. The process of producing and pouring cement grout into AC layers is conducted when AC layers are totally cool down, which is estimated at least 24 h after finishing the last rolling. Semi-flexible material is believed to have a better rutting resistance compared to that of the conventional AC, this is resulted from the appearance of cement grout. Furthermore, joints are not required in this kind of pavement. As the results, the significant advantages of the material are the combinations of those of AC and PCC. In this paper, the authors intend to access the rutting and indirect tensile strength of this material. The applications of semi-flexible material in the pavements of airport, airfield, port, warehouse and other high traffic areas are feasible.

Four-points bending tests were carried out on high performances concrete beams without stirrups and with stirrups, designed to consider shear behavior, and using digital image correlation technique (DIC). In the experimental device, the shear zone between the support and the loading point was digitized by high resolution camera. The numerical analysis of the recorded images is performed by Gom-Aramis software to obtain the deformation of concrete and to monitor the crack evolution in terms of width, spacing and length. The different models to determine the capacity of shear strength of reinforced concrete beams, used by the principal universal design codes such as the American ACI 318, the British Standard 8110, the European Eurocode 2 and the New Zealand NZS 3101, were extrapolated to high performance concrete to evaluate the applicability of these regulations originally developed for the ordinary concrete to the high performance concrete. The experimental results show that all the code models underestimate the shear contribution of high performance concrete and at the same time greatly overestimate the transverse reinforcement contribution. Among the four models, Eurocode 2 yields the best predictions of the ultimate shear strength of high performance concrete.

Fiber-cement stabilized soil is one of many methods for strengthening soil. However, the kind of fiber material used in this method plays an important role. So far, many researchers have studied on many kinds of fiber to stabilize soil such as rice straw, rice husk, pineapple leaf, banana leaf, etc. These fiber materials are abundant, cheap and easy to obtain from the agricultural field because most of them are discarded. Furthermore, the traditional way to dispose of agriculture waste is burning causing some environmental pollution problems. Therefore, the utilization and direct use of waste materials are of much benefit to environment and economy. Nowadays, corn is the third most cultivated crop in the world, so the by-product from corn such as cornsilk is redundant and easy to collect from the field. Hence, the present work aims to study the effect of new waste fiber material as raw cornsilk fiber in strengthening soil. This study uses the unconfined compressive test to evaluate the strength and strain of cemented soil and fiber-cemented soil. Soil used in this study is artificial soil, which is made of clay and silt with the ratio of 2:3, respectively. Cemented soil admixtures are made with cement contents of 30, 35, 40 kg/m3. The effect of fiber content is studied in this study by changing the fiber content added to cemented soil admixtures at different levels of 5, 10, 15, 20, 25, 30 kg/m3. The results of this study show that it is possible to utilize of cornsilk as fiber material in cemented soil stabilization.

In the South of Viet Nam, every year, a large amount of excavated sludge from construction sites has been disposed directly in the final disposal, but the recycling rate of sludge is low. Therefore, in this study, fiber-cement stabilized soil method was applied to recycle sludge in Viet Nam. Moreover, paper, rice straw, rice husk, and cornsilk were used as fiber materials in this method because they are waste materials and easily obtained in Viet Nam. Four kinds of fiber and cement were used to improve sludge and unconfined compression tests were carried out to collect failure strength and strain data. The experiments were performed under 28 mixing conditions. The water, fiber, and cement content were changed to find out which fiber material is the most suitable to modify sludge in Viet Nam. The results showed that rice straw gave the best results to modify sludge by using fiber-cement stabilized method.

Ground granulated blast-furnace slag (GGBS) is a common by-product used for decades in the cement and concrete industry, and having beneficial effects on environmental properties and durability of concretes. However, GGBS reacts less rapidly than cement and the short-term compressive strength of GGBS-concretes are usually lower than the ones of Portland cement concretes. The aim of this paper is to test the efficiency and evaluate the synergic effect of combining different activation routes (fineness of Portland cement and GGBS, use of chemical activation, and application of thermal cycles) on short-term compressive strength of GGBS-Portland cement-based materials. Results showed that the simultaneous use of all activation routes allowed blended cement with GGBS to achieve almost the same initial mechanical characteristics than Portland cement.

Reinforced earth structures, later known as Mechanically Stabilized Earth (MSE) walls, have been widely employed over four decades due to their ease of installation, quick construction compared to conventional reinforce concrete. Yet, numerous failures of MSE walls structure take place. Most of those failures are frequently attributed to the presence of water within or behind the reinforced zone, flow response inside reinforced earth structures as well. Recently, the use of “high fines” and/or “high plasticity” soils for reinforced fill has become more frequent due to the difficulties in finding an appropriate borrow pit. This paper utilized a well calibrated numerical model to perform series of parametric calculation of MSE incorporated with drainage composite, in which fine-grained poorly draining material was utilized as backfill. The experiments were conducted to investigate the influences of water retention characteristics of poorly draining materials utilized as backfills on the seepage response in MSE wall as subjected to rising of upstream water table. The flow response was examined in terms of effective saturation distribution, changes in phreatic surface as well. The calculated results show that the larger pore size yields the narrower zone of high saturation. The more uniform pore size yields narrower effective saturation profile in range of intermediate saturation zone. The moisture profile in reinforced soil mass is somewhat affected by flow properties of the soil placed next to reinforced part. The distribution of effective saturation at the interface between backfill and wall drainage composite is also governed by the capillary barrier which taken place at the interface between two materials having different pore size.

A Spray Test and the first test results on soil-cement mixture in the laboratory were presented in this paper. This device simulates the impact of rains on the walls or earthen walls. The results show a resistance to erosion by a rain of the soil-cement mixture, while the other materials were eroded by rains under the same precipitations.

Thermal power plants (TPP) generates wastes (bottom and fly ashes) which become a serious environmental problem in Vietnam. Indeed, although in several countries fly ash can be used for cement industry, fly ash from actual TPP in Vietnam does not have enough good quality for cement production, because the fly ash treatment phase has not yet included in the generations of existing Vietnamese TPP. That is why bottom ash and fly ash purely become wastes and their evacuation is an urgent demand of the society. This paper presents an investigation using fly and bottom ashes in the manufacturing of construction materials. The aim of this study is to propose a possibility to reduce environmental impacts of fly and bottom ashes, and manufacture construction materials having low embodied energy by using less cement. Several proportions of fly ash, cement, gravel, sand and water are tried to manufacture low strength concretes which can be used for non-load-bearing walls. Specimens are tested in uniaxial compressions. Results show that with a reasonable cement amount (4–8% by weight), by replacing cement by fly ash or replacing sand by bottom ash at 10-30%, the obtained materials can be used for non-bearing materials or low strength structural materials.

Limestone formations constitute a serious geological challenge for large building projects such as wind turbine farms. Indeed, limestone formations might be subject to karstic phenomena such as sinkholes or subsidence constituting a serious hazard for existing constructions and future civil engineering projects. In calcareous geological settings, a characterization of the subsurface to detect wealthy rocks is therefore mandatory. The classical approach consists in drilling boreholes and cone penetration tests to identify subsurface properties. However, they only provide punctual information whereas karstic environments show sharp variations with complex 3D geometry, making interpolation between boreholes relatively inefficient. In this context geophysical methods can provide spatially distributed information at a limited cost. In particular, surface electrical resistivity tomography (ERT) aims at mapping the distribution of electrical resistivity in the subsurface in a passive way using only surface sensors. The method is based on the measurement of electrical potential resulting from the injection of DC electrical current. In karstic contexts, weathered rocks generally show an increased porosity and water content compared to healthy limestones, leading to strong contrasts in their electrical resistivity. ERT is therefore particularly sound to investigate karstic phenomena. Most standard ERT applications use 2D profiles that are quick to acquire and interpret. However, in complex 3D geometries, the acquisition of 2D profiles is not sufficient to image correctly subsurface structures. 3D data sets require more efforts both for acquisition and interpretation, making their use more costly and therefore less common in practice. In this contribution, we propose an innovative 3D ERT acquisition procedure to reduce the field efforts and duration of the 3D acquisition procedure. The method is based on standard 2D parallel lines, but, in contrast with previous methodologies, we also acquire cross-line measurements in several directions to increase the ability of ERT to image 3D structures. To ensure a fast acquisition of large area, we limit the cross-line measurements to pre-defined line spacing and implement a roll-along technique moving previously acquired 2D lines in the perpendicular direction. The data can then be acquired with a standard 64 electrodes equipment. We first demonstrate the increased imaging capacities of our technique compared to standard acquisition methods with a numerical benchmark. Then, we validate it through a field application to detect the 3D geometry of karstic features and unaltered limestone formations. We analyze the minimum amount of cross-line measurements required for a proper imaging of the 3D structures. The proposed 3D survey induces extra costs of about 50% compared to a traditional 2D survey, but this extra cost is compensated by a largely better imaging of the subsurface. This cost will be reduced in the future by optimization of the survey to reduce acquisition time.

Shallow closed-loop geothermal systems are worldwide applied providing economical and environmental benefits. This paper presents an in-situ study of four Borehole Heat Exchangers of 100 m long, installed in an heterogeneous bedrock in the campus of the University of Liege (Liege, Belgium). A Thermal Response Test (TRT) of a heating phase of 7 months was conducted in one of the boreholes. During this test, temperature was measured at the pipe inlet and outlet, as well as along the four boreholes by the fiber optics. To further investigate the measured data, the test was simulated by 3D numerical modeling. The comparison of the measured data with the numerical results allowed to detect the critical parameters for the behavior of the BHE and for the temperature evolution in the surrounding rock mass. In this case study, the behavior of the BHE could be predicted based on the results of a typical-duration TRT (of a few days), considering the ground an homogenous and isotropic material. However, the thermal plume in the surrounding ground seems to be influenced by several factors, such as the bedrock heterogeneity, the distance to the heating source, air temperature variations and thermal effects at the borehole bottom end.

An elastoplastic constitutive model exhibiting particle crushing is developed based on the framework of continuum mechanics. The proposed model is formulated based on the extension of the critical state soil model [1, 2] to firstly incorporate the effect of packing density on the stress-strain characteristics by employing the concept of subloading surface [3]. Then, the effect of particle crushing is further implemented by incorporating the evolution of particle size distribution curve due to crushing stress and its effect on the constitutive behavior. Finally, the performance of the proposed model is validated with experimental test. The simulation results show that in spite of a simple formulation of the constitutive model, the behavior of crushable soils is well predicted.

The Norwegian Geotechnical Institute (NGI) has developed several calculation procedures over the past few decades where effects of cyclic loading are taken into account. This paper presents an undrained cyclic accumulation procedure used for offshore foundation design. A constitutive model called UDCAM was developed based on the NGI’s accumulation procedure and implemented into different finite element programs in order to better predict and optimize the offshore foundations. The UDCAM FE back-analysis of 1 g-model test of a gravity based structure in clay under cyclic loading was first performed for verifying the FE calculation procedure. The UDCAM model was then applied to analyze the undrained cyclic behavior of a large monopile to be installed at the potential offshore wind farm in the Korea Western Sea. The FE results were compared with the predictions obtained by the semi empirical (p-y) method recommended by API, which has been commonly used in the piled foundation design.

In this study, we tested the ability of geophysical methods to characterize a large technical landfill installed in a former sand quarry. The geophysical survey specifically aimed at delimitating the deposit site horizontal extension, at estimating its thickness and at characterizing the waste material composition (the moisture content in the present case). The site delimitation was conducted with electromagnetic (in-phase and out-of-phase) and magnetic (vertical gradient and total field) methods that clearly showed the transition between the waste deposit and the host formation. Regarding waste deposit thickness evaluation, electrical resistivity tomography appeared inefficient on this particularly thick deposit site. Thus, we propose a combination of horizontal to vertical noise spectral ratio (HVNSR) and multichannel analysis of the surface waves (MASW), which successfully determined the approximate waste deposit thickness in our test landfill. However, ERT appeared to be an appropriate tool to characterize the moisture content of the waste, which is of prior information for the organic waste biodegradation process. The global multi-scale and multi-method geophysical survey offers precious information for site rehabilitation studies, water content mitigation processes for enhanced biodegradation, or landfill mining operation planning.

Seafloor drilling systems are the latest innovative technology to explore the next frontier of ultra-deep water locations. Drilling, sampling and in situ testing (e.g., cone resistance and seismic velocities) are directly performed using the remotely operated seabed system. This paper provides a background of such seafloor drill technology and its benefits to the offshore industry. By reviewing an example from the field, the paper specifically discusses the performance of the system equipped with a dual-array cone for measuring in situ shear wave velocity in deep water sediments. These field measurements of shear wave velocity corresponded favourably with the advanced laboratory testing on intact, recovered samples. They also can be employed in conjunction with cone penetration testing in order to provide a high confidence shear wave velocity profile for deep water sediments for engineering purposes.

In the range of vertical ground heat exchanger borehole and energy pile, heat is diffused from the heat pipes into the concrete and then to the surrounding soil. The heat transfer process usually follows three main mechanisms: conduction, convection and radiation. Among them, the heat conduction due to temperature gradient is the most relevant process associated with heat transfer in soil and pile. The review of conduction heat transfer models applied to vertical heat exchanger borehole and energy pile shows that the existing models can be classified into two groups, the first one is applied in homogeneous media and the second one is applied in composite media. Most of these models are generally suitable for the case of steady state conduction of heat exchanger boreholes. However, energy pile foundation has larger diameter and smaller length than that of the borehole. As a result, heat transfer inside the pile will take a longer time to reach the steady state. In this paper, a new solution of conductive heat transfer based on the transient heat model is presented. This solution is applied for energy pile and is validated by using the solution of finite element method.

Dynamic impedance of pile groups is dependent on soil parameters, i.e. soil unit weight (ρ _s ), Poisson’s ratio (ν), shear modulus (G _s ), shear wave velocity (V _s ) and damping ratio (β _s ). The last three soil parameters (G _s , V _s & β _s ) strongly depend on the strain level caused by propagating seismic waves. Near surface (30 m depth) values of soil design parameters (G _s , V _s & β _s ) are normally used in design and these are influenced by variation in soil properties like plasticity index (PI), over consolidation ratio (OCR), effective stress (σ’), depth of soil strata over bedrock (H) and impedance contrast ratio (ICR) between the strata and the bedrock. The aim of this study was to investigate the sensitivity of dynamic pile-group impedance to variation in soil design parameters (G _s , V _s & β _s ) caused by variation in soil properties for a typical bridge that was founded in site classes C and D according to the AASHTO Code and were subjected to a suite of actual earthquake ground motions.

Unconfined compressive strength (UCS) and uniformity of soilcrete are strongly influenced by deep mixing equipment and its operating parameters. Soil cement mixing was applied to reinforce the two sections of earth levees (1) 60 m long in An Giang and (2) 30 m long in Dong Thap using a mini light-weight soil-cement wet mixing system, named as a NSV system. Core boring was employed to take field soilcrete samples and UCS tests were conducted to investigate soilcrete characteristics. The operating parameters were save in the built-in memory of the NSV system during construction. This paper instigated the proper operating parameters such as mixing energy, penetrating/lifting speeds, rotation speed, and mixing duration to optimize the NSV system for the Mekong Delta conditions. The results indicate that the field soilcrete achieved high UCS and uniformity along soilcrete columns with the mixing time of 800 times/m, mixing duration of 2.5–3.5 min/m, rod rotations of 40–50 times/m (penetration) and 70–80 times/m (lift), penetrating speed of 0.5 m/min and lifting speed of 1.2 m/min.

Due to their various applications in geo-environmental engineering, such as in landfill and nuclear waste disposals, the coupled chemo-hydro-mechanical analysis of expansive soils has gained more and more attention recently. These expansive soils are usually unsaturated under field conditions; therefore the capillary effects need to be taken into account appropriately. For this purpose, based on a rigorous thermodynamic framework [2], the authors have extended the chemo-mechanical model of Loret el al. [5] for saturated homoionic expansive soils to the unsaturated case [3]. This chemo-mechanical unsaturated model is subsequently applied to simulate the behaviour of triaxial samples subject to combined chemo-mechanical loadings under laboratory conditions to investigate its precision and pertinence in view of future refinements.

This paper presents a numerical modeling accounting for the effect of cracking on both mechanical and hydraulic properties of unsaturated rocks. Firstly, the constitutive model developed by Bui, et al. [3], established in the framework of thermodynamics of porous media, is recalled. Its main feature is that damage intervenes on both mechanical behavior and hydraulic properties (water retention curve and hydraulic conductivity). Secondly, the model is validated against experimental data on an argillaceous rock. Finally, this constitutive model is implemented into a domestic finite element code to study numerically the evolution of hydromechanical responses of a radioactive waste underground gallery during a simplified life cycle. Numerical simulations demonstrate the consistency of the model and highlight the influence of desaturation on the hydromechanical behavior of the gallery.

Large differential settlement (e.g., >30 mm) of bridge approaching embankments behind abutments in service has caused difficult travel for vehicles. The current techniques to reduce large settlements such as pavement refilled are still ineffective and less sustainable. Jet Grouting has high potential application to treat large settlements but has limit applications. This paper attempted applying the Jet Grouting to reinforce bridge approaching embankments in Vietnam. The Tam Bang and Vam Dinh bridges on the DT852 highway in Dong Thap province were investigated and reinforced using the Jet Grouting technology. The primary consolidation settlement analysis indicates that (1) the Jet Grouting technology has full capacity of mitigating large differential settlements of the Tam Bang and Vam Dinh bridges, (2) The proposed solutions can gain public trust, (3) Jet Grouting technology has high potential applications to reinforce differential settlement of bridge abutments in the Mekong Delta.

This work aims at investigating the evolution of local friction mobilized at the pile-soil interface, focusing on small amplitude and large number of displacement controlled cycles, corresponding to fatigue behaviour (10^5 cycles). An experimental program has been conducted in a calibration chamber with an instrumented pile-probe installed and loaded in reconstituted specimens of saturated clay.After describing the testing setup and the experimental procedure, a typical test is presented, carried out on a reference French kaolinite to evaluate the local friction mobilized upon different monotonic loadings and its evolution during the application of displacement-controlled cyclic loading. Quasi-static displacement-controlled compression tests are carried out before and after the cyclic sequence in order to evaluate the influence of the cyclic sequence on the mobilized static local friction after cycles, as compared to the initial friction mobilized. The displacement-controlled cyclic test allows to observe an initial phase of friction degradation which starts progressively from the very beginning of the cyclic sequence (cyclic softening), followed by a stabilization phase until the end of the test. The evolution of mobilized friction during the application of the cycles is quantified by introducing a coefficient of evolution which allows to clearly visualize the degradation and reinforcement phases. The local shaft friction evolution, upon the cyclic loading, is interpreted in terms of the combination of excess pore water pressure generation and dissipation which develops during the cyclic sequence and controls the evolution of effective normal stress acting on the soil-pile interface. A comparison is made between maximum static shear mobilized before the cycles and after the cycles, showing a clear influence of the cyclic sequence on this quantity. Finally, the repeatability of the test is checked, showing a fairly good level of repeatability.

This paper presents a numerical study on the desiccation cracking process of clayey soils. The initiation and propagation of cracks are investigated using a finite element code including damage-elastic cohesive fracture law to describe the behaviour of cracks. The coupling between the hydraulic behaviour (moisture transfers in the soil matrix and in the cracks) and the mechanical behaviour (volume change of the soil matrix and development of cracks) is also considered in the code. The results of laboratory test performed on a clay soil, taken from the literature review, are used to evaluate the numerical modelling. The results show that the code is able to reproduce the main trends observed experimentally (i.e. the shrinkage related to drying, cracks development).

A huge amount of soft soil is dredged by grab dredger or pump dredger at many ports every year to maintain enough sea route and sea berth. These soft soils used to be transported and dumped out to a disposal site or land reclamation site. It is becoming more difficult to construct any disposal area for dredged soil and subsoil. In order to prolong the service life of the sites, beneficial use and volume reduction of the dredged soil are desirable. The pneumatic flow mixing method was developed in Japan for beneficial use of dredged soil, land reclamation and land development, in which dredged soil is mixed with relatively small amount of cement in a transporting pipeline. The soil mixture forms several separated mud plugs in the pipeline, and is thoroughly mixed during the transporting. The mixture transported and deposited at reclamation site gains relatively large strength rapidly so that no additional soil improvement is required. This method is expected to promote the beneficial use of dredged soil and to provide an economical and rapid construction for land reclamation, and was applied to the Central Japan International Airport and Tokyo/Haneda International Airport. In this article is described briefly the development of pneumatic flow mixing method and its two large scale applications as well as the mechanical properties of the stabilized soil.

The slip line theory is applied to the problem of an axisymmetric retaining wall interacting with unsaturated soil. Active and passive failures of a rigid vertical wall are considered. The slip line governing equations assume the limiting equilibrium state of a Mohr-Coulomb soil. A linear variation of the contribution of suction to the effective stress with depth is assumed. A standard finite difference method is used to solve the governing equations. The finite difference procedures were validated with recently published literature on axisymmetric retaining walls retaining dry soils. It is shown that adopting the effective stress concept enables the influence of suction in unsaturated soils to be considered in a simple way. An example of analysis is presented to illustrate this. Moreover, the paper shows significant influence of the length scale and the magnitude of the circumferential stress on computed earth pressures.

This paper presents the reservoir pressure depletion will cause rock stress changes, which results in an increasing likelihood of serious sand production in the unconsolidated sandstone reservoir. This paper aims at offshore unconsolidated sandstone oil reservoir, analyzes rock stresses of the borehole wall with impact of reservoir pressure depletion on in-situ stresses on rock strength. A full review basic theory in geomechanics will be presented, such as: rock failure criterions, sanding critical drawdown pressure calculating model and a numerical calculating method for the model are developed. Furthermore, a case study sanding prediction method for pressure depletion of offshore oil reservoir in Cuulong Basin, Vietnam also is presented. Using the model analysis, on the other hand the chart of sanding onset is relatively large with the high formation pressure depletion. On the other hand, the sand will be appeared no matter how small the drawdown is.

This study evaluates the feasibility of incorporating bottom ash and red mud into a binder to stabilize soil. In this study, the bottom ash collected from Honam Thermal Power Plant in South Korea was ground to decrease particle size. It was then coupled with red mud to form a new binder based on the geopolymer synthesis theory. Sodium silicate solution (Na₂SiO₃) in terms of alkaline-activator was added into mixture to enhance the activity of binder. Weathered granite soil which is classified as SM in USCS is the target of stabilization. Unconfined compressive strength of stabilized soil and heavy metal content of leachate were examined. Experimental results showed that ground bottom ash coupled with red mud can be used to stabilize weathered granite soil at the ambient curing condition. The highest compressive strength of stabilized soil was 4.1 MPa. Red mud in certain limits has contributed to the increment of soil strength, however, the long-term strength decreased with the increase of red mud content. In addition, based on the results obtained with leaching test, it can be concluded that leachate from the stabilized soil is not harmful to the environment.

This paper focused on the quantitative evaluation of thermal conductivity of CLSM made with excavated soil and coal ash for a possible use as thermal grout for borehole heat exchangers. In a preliminary study, control mixtures were produced with Portland cement or cementless binder, Class F fly ash, and ponded ash. Then, for other mixtures, excavated soil substituted for ponded ash in amounts of 10, 20, 30, and 40% by weight. A series of laboratory tests including bleeding, flowability, initial setting time, and unconfined compressive strength were carried out in accordance with applicable ASTM Standard. Afterward, thermal conductivity was measured by using thermal needle probe, conforming ASTM D 5334 to verify the feasibiliy as thermal grout for borehole heat exchangers. The test results presented herein showed that the engineering properties of CLSM with excavated soil, possibly up to 30%, satisfied the specifications of ACI 229R. Moreover, an increase of excavated soil amount in CLSM could lead an improvement in thermal conductivity.

Hydro-mechanical behaviors of a saturated clay with various strain-rate and different stress histories are investigated through a series of consolidated-undrained and K₀ consolidated undrained (K₀CU) tests which were conducted on reconstituted specimens. The samples were taken from an excavation site in Macau and reconstituted in the laboratory to provide homogenous specimens. A total of four CU tests and four K₀CU tests were undertaken on 38 mm diameter samples. The samples were saturated first by use back pressure saturation method (back pressure 200 kPa), after saturation, they were loaded to a confining stress 400 kPa and then unload to 50 kPa, 100 kPa, 200 kPa, 400 kPa (OCR = 8, 4, 2, 1) and finally were sheared at constant shear rate (0.1%/h, 1%/h, 10%/h) to failure. In this research the responses of marine clay under various strain rates under different OCRs on the strain-rate effects will be discussed, parameters for accounting the strain-rate effects on undrained shear strength will be proposed.

In several cases where high quantities of steel reinforcements are needed at reinforced concrete (RC) beam-column joints, headed bars are employed as a solution to facilitate the placing of reinforcement bars. This paper establishes a new formula for the prediction of the shear strength of exterior RC beam-column joints where beam longitudinal reinforcements use headed bars. A database was collected, which contains most of available test data of exterior beam-column connections using headed bars and subject to quasi-static cyclic loading. First, influences of the key parameters for the joint shear strength of the connections were evaluated by using the collected database. Then, three most important parameters were chosen to develop a formula for the prediction of the joint shear strength. The accuracy of the proposed formula was evaluated by comparing the predicted joint shear strength using the proposed formula and that of 30 experimental exterior connections collected from different sources, and also with predicted values using two existing analytical models. This evaluation showed a better relevancy of the proposed model in predicting exterior joint shear strength, compared to the existing formulas

SFRC is increasingly used for structural applications. The present paper is devoted to a probabilistic explicit cracking model developed since 1985. It is used to analyze the cracking behaviour of different SFRC beams submitted to different loading conditions: bending and shear. It is demonstrated that this numerical model is fully capable to provide precise information about the cracking process related to this types of structural behaviour, especially concerning the cracks opening evolution.

Man-made structures are erected according to a requirement to serve a useful purpose, either to an individual, organization or society as a whole. If we take the example of a building structure, it protects its occupants from the environment. The first set functional requirements will be to keep out annoyances like noise, rain, cold, ice, snow and heat. In our radically changing world, new and more onerous requirements need to be considered, ranging from noxious pollution to the possibility of the structure having to withstand an extreme natural hazard, like with an earthquake or tornado. The fact is that structures, whether making up the fabric of our habitable buildings or supply infrastructure, need to be robust against the various annoyances and accidental situations that the structures will be exposed to. The generic damage-effect of climate change will likely make “natural” hazards much more extreme and potentially dangerous in the future. Climate change effects have the likelihood of radically degrading and bypassing the safety barriers of previously engineered design bases. In addition, due to the way in which our civilisation has evolved to the present day, with its commodity trade and service networks, our society more exposed and vulnerable to severe and potentially extreme shock-hazard scenarios. People and organisations implicitly depend on their structural fabric to be functional and safe. Regardless of the great diversity of structures, the one unvarying expectation is that they are robust enough to safely protect the structure’s users throughout their intended life period. However, judgements by structural engineers allied with interpretation of design codes and standards can vary greatly. There being a difficult balance between economy of construction and the ultimate robustness of the structural design solution.This study paper investigates the relationship between robustness of our structural fabric and how important it is to achieving a resilient society, where people are safe, organisations are stable and the economy is sustainable. Essentially we will outline the key quantities that link structural robustness to societal resilience, and whether this crucial relationship is adequately reflected in application of structural design code and standards practice. The thinking logic and methodology provided in this CIGOS 2017 paper will take these key considerations and factors related structural robustness and resilience, the two principal parts of this paper encompass:-Risk Analysis in relation to Robustness.Qualitative - Holistic Systems Thinking;Quantitative - Risk Analysis (QRA);Reasons for Poor Structural Robustness.Future Coping and Adaptability.Structural robustness and resultant resilience;Future design objectives;Specific design principles and options.

The BatiPack® process is an innovative system for the construction of load-bearing walls with controlled costs and delays. The wood brick, hollow, contains isolating within it, are maneuverable and designed to be assembled quickly and easily without any special skill and without lifting equipment. By its mechanical, ecologic characteristics, the process thus perfectly substitutes for traditional masonry materials. It can be adapted to any type of project and size of building.Delivered on pallets, it is easily transportable and can be stored anywhere. The assembly is made by nesting and gluing in a groove. The prestressing put in place by a cable positioned on each side of each block gives the system lightness, minimal consumption of raw material and above all flexibility combined with high strength.All types of coatings can also be placed on the BatiPack which also offers maximum thermal resistance, thanks to insulated materials which are integrated inside of the blocks. The customer has the choice between wood fiber, wool of rock, of cotton or of soil.This process has various mechanical properties and has a high seismic resistance.

In recent years, Glass Fiber Reinforced Polymer (GFRP) bars have become an alternative to steel reinforcement in concrete structures. Due to the relatively low modulus of elasticity and the different surface treatment, the problems of bond between the GFRP bars and the concrete should be carefully considered. This paper focus on the experimental evaluation of the bond–dependent coefficient (k_b) of GFRP bars according to the ACI 440.1R-06. This coefficient takes into account the degree of bond between the GFRP bar and the surrounding concrete and was used in calculating of serviceability limited state of concrete structures.

In this paper, the strengthening of two-way reinforced concrete (R/C) slabs using Carbon Fiber Reinforced Polymer (CFRP) sheets is evaluated experimentally. Five identical square R/C slabs with 1200 mm side length and 60 mm thickness were constructed and tested to failure under a monotonic central loading point. One un-strengthened slab was used as reference slab while four slabs were strengthened with CFRP sheets. The obtained results of this experimental research have shown the flexural behavior of strengthened slab by CFRP materials and the strengthening effectiveness for moment resist of R/C slab using this material.

This paper focuses on a technique developed to monitor and track automatically the crack propagation at two sides of the corner of a coupon to investigate the corner effect on the fracture toughness of the high strength cold-formed steel channel sections. The coupons taken longitudinally along the corners of channel sections were initially pre-cracked at both sides under fatigue loading and then loaded monotonically under tension until failure. When assessing the fracture toughness, it was particularly important to identify the precise moment of initiation and propagation of the pre-existing cracks. The technique was based on image processing with a grid of circular targets attached on the surface prior to the monotonic test and used for scaling and orientating all acquired images. A digital correlation procedure was applied to track both edges of the notch of each crack and quantify its opening during the test. By correlating the changes in the rate of crack mouth opening, the different stages of propagation could be identified together with the corresponding critical loads. The fracture toughness is determined based on these critical loads which could not be captured directly from the load versus axial displacement curves.

During the first step in the development of any structural system identification method, the method should be validated by noise-free measurements in the first place. Nevertheless, this assumption is far from reality as the measurements in these tests are always subjected to the errors of measurement devices. To fill this gap, this paper analyzes the effects of measurement errors in a parametric structural system identification method: the observability method. To illustrate the symbolic approach of this method a simply supported beam is first analyzed in detail. This simulation provides the parametric equations of the estimates. Then, the effects of errors in a particular measurement, errors in all measurements, load locations are studied in this structure. Two additional examples of increasing complexity are also analyzed to show the effect of modelling errors on the estimates. A fluctuation of the observed parameters around the real values is proved a characteristic of this method. The results of these structures illustrate how important the effects of modelling errors are especially in areas with low curvatures.

This article presents the main results of an extensive series of tests on a small-scale earth pressure balance tunnel boring machine. The results concern the soil/machine interaction behaviours during excavation. Some analysis performed at a small scale is compared to data from work to extend Paris metro line 12.

This paper focuses on the influence of the contact surfaces between autoclaved aerated concrete blocks (AAC) and the surrounding reinforced concrete frame. From the experimental results and from the model proposed by the authors, different behaviors between ideal and real models have been analyzed and compared given a variety of aspects: the stiffness degradation, the drift, the cracking peak, the strength, the ductility and the energy dissipation. The research aims to provide parameters for calculating work approaching the actual behavior to obtain safer and cost-saving construction.

Recently earthquakes with quite high magnitude have continuously occurred in the Vietnam territory which cause the dangerous to masonry buildings. The stringent seismic design requirements for masonry structure will be therefore considered in the construction field of Vietnam. The paper, which an exploratory study, focuses on the behavior of clay solid brick masonry walls, especially walls repaired on both sides with TRC (Textile Reinforced Concrete) composite under cyclic in-plane loading condition. This work is the first step towards defining the potentiality including both technical and scientific aspects of using TRC in seismic strengthening and repairing the masonry structure in Vietnam. Thus, an experimental program has been performed at laboratory scale. Two walls have been submitted for cyclic shear-compression tests in-plane solicitation: the first one (unreinforced wall) is tested to the pre-defined damage level and failure mode, and then repaired with TRC strips as the second one. A comparative study on global behavior and on mechanism of failure is performed and, although the limited number tests, highlights that, thanks to the contribution of TRC strips, the wall’s residual strength and deformation ability are upgraded. In addition, compared to the unreinforced specimen, the repaired one is more stable strength and stiffness change at later stages. Furthermore, the TRC strips help to reduce the risk of out-of plane failure. However, it seems to be that, the low reinforcement ratio and (or) the relatively unsuitable formulation of mortar, especially the grain size, in TRC limit its efficiency in reinforcing solutions.

The concept of frequency band gaps that has been widely used in many disciplines of physics and semiconductors is extended to other phenomena such as seismic vibrations. This paper presents the potential of an approach based on periodic arrays to protect a site from seismic effects. The scheme consists of a periodic arrangement of inclusions that act as a barrier to divert or attenuate the propagation of the seismic waves. The aim is to seek large low frequency gaps within the range of the earthquake ground motion frequency content. To this end a numerical study of two periodic arrays (1D and 2D) has been conducted to bring out the potential to block the propagation of seismic surface waves. The obtained numerical results show that under certain conditions, a band gap can be shifted to the low frequency range (7.91 to 21.13 Hz) which is suitable for application in seismic engineering. It is recognized that the models used in this study are very simplistic compared to reality, and therefore more research work is needed to corroborate these results by investigating the transmissibility of the system with different materials and configurations.

Climate change hazards and malicious attack threats are major problems that the world must start to mitigate, prepare for, cope with and adapt to. A more holistic approach to severe event-hazard/threat risk assessment thereby accounts for the infrastructure’s damage, the scale and capability of preparedness, the success of response and final recovery actions, investigating the complete coping cycle for the particular socio-technical system of interest. A holistically based coping test method has been developed by Arup, called the “Holistic Integrity Test” (HIT). In broad terms for application, there are 10 key risk-related socio-technical system integrity factors that will advise governing authorities of their region’s coping capability against natural geo-hazards, including the effects of climate change, but also malicious attack threats.

The Direct Strength Method (DSM) design rules for cold-formed steel members have been incorporated recently into the North American specification for the design of cold-formed steel structural members (AISI S100-12) and the Australian cold- formed steel structures standard (AS/NZS 4600:2005). The method covers the design of structures with and without holes subjected to compression and bending and without holes for shear. Recent research has extended the DSM to the design of beams with holes predominantly in shear. This paper reviews the DSM design guidelines for perforated members in compression and bending and the latest research on the DSM for perforated beams in shear.

In the future, the world and civilised society with its complex infrastructure shall be exposed to more severe and potentially risky hazard and shock scenarios. Climate change will amplify severe hazards into extreme conditions never before experienced. Climate change is an emerging reality in a much more complex and interwoven set of considerations encompassing economic development, population growth and the need for political awareness and real action to be taken. We are also becoming more vulnerable to malicious shock attacks caused by criminal, anti-political and terrorist activities, including situations that involve physical damage, but also “soft-transmitted” cyber-attack aimed at our densely coupled communication and data networks. As scientists, engineers and managers in the carbon-free nuclear industry, it is judged that we need more holistic approaches to risk and hazard assessment that are able to substantiate that the infrastructure is not only robust and resilient enough to withstand the impact, but also to test the capability and effectiveness of the overall ‘wider-field’ coping strategies; including not only the plant itself, but also the site, the adjacent region and the resident country-wide infrastructure and resource capability. Resilience essentially depends the ease and success for passing through the “coping cycle”.

A modal model comprising natural frequencies, damping ratios and mode shapes called modal parameters, is always appreciated due to its appropriate interpretation for physical phenomenon. For real structures, the modal parameters can be obtained from an operational modal analysis that offers several advantages: simple equipment thus low cost, continuous use, real boundary conditions. However, the excitation not controlled and not measured is always assumed as white noise in the operational modal analysis. In presence of harmonics on excitation, the white noise assumption is not verified and that makes the modal identification process difficult, even leading to biased results. A transmissibility function defined by ratio in frequency domain between two responses, is known as independent of excitation nature. This study proposes therefore to apply the transmissibly functions for modal identification in presence of harmonics. The proposition is validated by numerical examples and an experimental test.

Unibridge® is a pre-designed and prefabricated modular steel bridge system. It is a simple, robust and durable structure suitable for use in emergency situations and as a permanent bridge. Unibridge® is a modular predesigned and prefabricated steel bridge system. It has been designed for international load classes and can be built in single lane or multi-lane road width. It uses either a steel deck system with anti-skid coating or concrete deck.Unibridge® is constructed from prefabricated girders either 11.4 m or 6 m length. They are pinned end to end and connected transversely with spacers which allows for the installation of a steel deck with anti-skid coating or a concrete deck in-situ. The prefabricated girders are provided in three different heights (1 m, 1.25 m and 1.6 m) and the span of the bridge dictates which girder to use.Multi-span bridges can be built to achieve bridge lengths up to 57 m. As with single span bridges, Unibridge® multi-span bridges can be cantilever launched from the home bank to the far bank.

Bioclogging or the process that biofilm is conditioned for the development in porous media, leading the biomass accumulation in pore spaces and reducing the permeability of porous media that impedes fluid flow. Numerous research has focused on the study of bioclogging, but the process is very complicated and still poorly understood. This results in various permeability models that are only capable of predicting under certain conditions. In the study, we aim to mathematically develop a macroscopic model to predict permeability reduction in the saturated biofilter. The model adopts the concept that permeability reduction results from two mechanisms: pore radius reduction and pore plugging by mass accumulation. In the former, porosity, grain sizes, tortuosity and bulk factor determine the magnitude of permeability reduction. The pore plugging, in the other hand, interprets recent experimental findings of straining process in deep bed filtration that clogging in pore throat can be induced by deposited particles with the diameter many times smaller than that of pore throat. The model proves its capacity by obtaining a good match to a wide range of experimental data in predicting: permeability of clean porous media and magnitude of bioclogging in the biofilter.

Diffusion mechanism study of mass transport has received much attention in geo-environment domain, especially in waste containment applications. Diffusion of a substance in a homogeneous porous medium is traditionally modeled by Fick’s law. However, natural geology environments are often heterogeneous and thus that requires advanced models enabling to capture diffusion behavior in such media. “Double-porosity” medium concept can be replaced a class of heterogeneous media in which there exists two macro- and micro-porosity domains with very contrasted hydraulic properties, fractured rocks or aggregated soils, for example. In this paper, the development of a macroscopic model for pollutant diffusion in unsaturated double-porosity medium is presented, applying a multiscale method. The resulting model consists of coupled two equations for the diffusion in the macro- and micro-porosity domains. The effective diffusion tensor representing for the double-porosity medium is also obtained. The developed model is verified by comparing with the reference solution of the fine scale model through a numerical example of hydrogeology problem.

In this paper we present an experimental study of foam flow in porous media dealing with 1D sandpacks columns and 2D laboratory pilot. 1D porous column were dedicated to the study of foam generation and propagation in porous media of different permeabilities. We show that the resistance factor (RF) to flow, that is the ratio between pressure drop in presence of foam and pressure drop in absence of foam, is a non-monotonous function of permeability. A 2D transparent laboratory pilot (1 × 0.5 × 0.02 m3), made of two water saturated sand layers of different permeabilities has been used to visualize foam flow. We clearly see that foam remains in high permeability layer and does not enter in the low permeability one. Moreover when we inject a liquid tracer we see that fluid velocities are quite similar in both layers showing the front straightened up.

Synthetic dye is a widely used product, but dyeing industrial effluents have adversely impacted environment. During dyeing processes, 12% of dye input is wasted, and approximately 20% of this amount is discharged to the environment. In this study, Electro Fenton (EF) system was applied to treat a textile wastewater. H₂O₂ forming was accelerated by aeration at 1 l_air/l_sample/min and graphite electrode was used to reduce investment cost. Response surface methodology - Central composite Design (CCF) was used to investigate the effects of pH, Fe2+ concentration, and voltage on the removal efficiency. At pH 2.78, Fe2+ concentration of 2.0 mMol/l, and voltage of 16 V, the treatment system reached its optimum operating condition. Under this condition, color and COD (Chemical oxygen demand) in the effluent were 57 ± 2 Pt-Co and 56 ± 1 mg/l, respectively, after 30 min of treatment which met the national standard (QCVN 13:2015/BTNMT, column A).

Commercial activated charcoal was investigated for removal of Cr(VI) from aqueous solutions. The effects of altering the initial Cr(VI) concentration, pH, contact time and amount of activated charcoal were studied. Maximum adsorption of Cr(VI) was achieved between pH 1–3 and after a contact time of 120 min. The percentage of Cr(VI) removed decreased from 99.99–90.83% when the initial Cr(VI) concentration was increased from 0.05–0.5 mg ml−1 at pH 2 and 26 ± 2 °C. Various kinetic models such as pseudo first-order and pseudo second-order models were used to evaluate the mechanism of Cr(VI) adsorption on activated charcoal. The Cr(VI) removal process was found to be governed by second-order kinetics and the rate constant of the adsorption (k₂) was 0.1800 g kg−1 min−1 for an initial Cr(VI) concentration of 0.1 mg ml−1. The adsorption of Cr(VI) was evaluated using Langmuir, Freundlich, and Temkin isotherms and their constants were determined. The maximum adsorption capacity obtained using the Langmuir isotherm model was 45.24 g kg−1 at pH 2.

Extremely acidic groundwaters (EAG; pH < 3) are frequently observed in the Mekong Delta area. This study geochemically investigates the processes for this phenomenon. Forty-two groundwater and eight sediment samples were collected and performed chemical/mineralogical analyses and leaching experiments. Long-term data from 178 wells of National Groundwater Monitoring Network of the Southern Vietnam (NGMS) were also inspected. In the study area, groundwaters are characterized by increasing concentrations of various species such as SO₄, Fe, Mn, Al, Pb, Cr, Zn and U at low pH. SO₄ (up to 2959 mg/L) and Fe (up to 1679 mg/L) concentrations in the EAG are generally very high. Framboidal pyrite grains are typically observed in the sediment samples taken from the sites where acidic groundwaters were observed. The leaching experiments with those sediments using deionized water derived pH as low as 2.7 and high metal concentrations in the extractants. Heavy metal concentrations were also high in the extractants of pyrite-free sediments when the pH was adjusted to acidic range. Our results suggest that the high metal concentration in the acidic groundwater are closely related with the low pH induced by the pyrite oxidation. This study also shows that the acidic pH of groundwater is in part related with the well installation; that is, well installation chemically disturbs the confined aquifer, which was originally under reducing environments, and triggers the pyrite oxidation.

In this study, we developed a simple and convenient one-step method for activation of graphite using high basic red mud slurry to produce a mixture of red mud/graphene (REEG) under mild reaction conditions. The wet red mud was mixed up with graphene by direct electrochemical exfoliation of graphite in its solution. The REEG obtained was characterized and applied for removal of Cadmium (Cd(II)) from aqueous solutions. The effects of pH, contact time, and initial concentrations on the removal of Cd(II) were investigated. A removal efficiency of 98.95% at pH 6 was obtained after 60 min of adsorption, via the dispersion of 0.1 g of REEG in Cd(II) stock solutions (50 mL, 1 ppm). The maximum adsorption capacity (q_max) was calculated to be 12.598 mg/g. Results showed that REEG is effective for removal of Cd(II) from aqueous environment, which could also act as an effective adsorbent for the removal of other heavy metals from polluted water.

In this work, ZnO nanorods and Graphene-ZnO-PdO nanocomposite was synthesized through hydrothermal method. Crystallinity of the materials has been studied using X-ray diffraction (XRD) and morphology was analysed through Field Emission Scanning Electron Microscopy (FE-SEM) and Transmission electron microscopy (TEM) techniques. The synthesized nanomaterials are used for the photocatalytic degradation of Methylene Blue (MB) under UV-light illumination (365 nm) and the results were compared with commercial ZnO material. Graphene-ZnO-PdO nanocomposite exhibits higher degradation of MB under UV-light illumination than ZnO nanorods and commercial ZnO material. These nanocomposite materials can so be used for methylene blue MB photodegradation as for textile wastewater treatment.

To improve denitrification and phosphorus removal in VFCWs, the French company SCIRPE has developed a patented process called Azoé® which comprises biological pre-treatment on a trickling filter followed by two stages of partially saturated vertical flow filters planted with reeds. Phosphorus removal is carried out by addition of FeCl₃ at the outlet of the biological trickling filter. Phosphorus thus precipitated accumulates mainly on the surface of the first filter in the form of a sludge layer. After several years of operation, this surface layer represents a stock of phosphorus potentially mobilizable as a function of the biophysicochemical conditions of the environment. However the fate of organic and mineral micropollutants, (pharmaceutical residues, pesticides, metals, etc.) in the system is poorly known. In the present study, the performance of these systems was studied by monitoring an Azoé® plant in operation. The results confirmed the very good efficiency in carbon and nitrogen treatment, the good stability of phosphorus retention, and a high rate of removal or retention of most micropollutants analyzed.

This research conducts a slaughterhouse wastewater study with high nitrogen concentration by applying intermittent cycle extended aeration system (ICEAS) model combined with and without Mutag BioChip media to assessing the efficiency of this treatment. A model made from poly acrylic with a capacity of 18 L was utilized to evaluate COD and nitrogen removal efficiency for different organic loading rate (OLR). The results showed that removal efficiency of the ICEAS model combined with Mutag BioChip media was higher than one of the ICEAS model without Mutag BioChip media in terms of COD; $$ \text{NH}_{4}^{ + } $$NH4+-N and TN parameters. At the OLR of 0.5 kg COD/m3.day, the corresponding treatment efficiency of these parameters was of 91.48%; 87.08% and 83.59%, respectively. In the case that the OLR increased up to 2.0 kg COD/m3.day, the corresponding treatment efficiency only decreases slightly. It proves that the use of Mutag BioChip media allowed to increase the removal efficiency for slaughterhouse wastewater treatment.

Three scenarios for stormwater management in a 6.5 ha industrial area are investigated: (S1) separate stormwater pipe system with a downstream infiltration tank, (S2) succession of infiltration swales along roads and (S3) vegetated roofs and infiltration swales. Long-term simulations of the three scenarios are carried out with 6 min time step rainfall and evapotranspiration time series over 21 years (1992–2012). The model combines the Canoé® software for sewers and Matlab® codes for infiltration tank, infiltration swales and vegetated roofs. In scenario S1, the separate stormwater network includes 535 m of pipes and a 1600 m3 downstream infiltration tank. In scenario S3, all roofs are vegetated, with a storage capacity of 32 mm/m2, allowing to divide by two the total length of swales compared to scenario S2 (408 m and 203 m respectively) with impervious roofs. Vegetated roofs allow a mean decrease of 42% of the annual runoff volume. Continuous simulations allow to study in detail the hydrological behavior of the infrastructures at all time scales (from the time step to multi-year scales) and analyze statistically the results.

Prestressed concrete (PC) cylindrical tanks are used in industrial applications as liquid containing facilities, and are commonly constructed as base-supported structures with their associated foundations poured in place. In land-space constrained countries, however, it becomes viable to construct such facilities on sea as floating structures. This study deals with the design of an innovative self-stabilizing floating fuel storage tank. For this new type of fuel storage facility, the self-weight of the tank and the in-fill fuel are automatically balanced by the buoyancy force, and there is no need for vertical supporting foundations. Furthermore, the hydrostatic pressures on the tank wall due to outside sea water and in-fill fuel balance each other to a great extent, leading to significant reduction in material consumption and construction costs. Due to the absence of specific guidelines and engineering practices, it remains unknown whether PC floating self-stabilizing fuel storage tanks are applicable in the offshore environment. In this study, a comprehensive stability analysis was first carried out to determine the geometrical dimensions for tanks of different capacities varying from 5,000 m3 to 15,000 m3 in order to meet the operational requirements. Finite element (FE) models were then developed to assess the structural performance of a selected tank of 12,500 m3 capacity when subjected to self-weight and hydrostatic pressure. Based on the analytical results, potential technical challenges were identified and design recommendations were further provided.

Nuclear power, to most of us, is mystic and somehow scary, and despite its drawbacks, is still playing an important role in the world wide energy supply. However concrete, without mystery as the most widely used materials in construction, is used as a major constituent for nuclear facilities such as radioactive waste repositories and nuclear power plants. Concrete is the only practical material offering a number of advantages including sufficient shielding against the dangers of radiation, good compressive strength, low cost, easy building, and retention of radionuclides limiting their dissipation. The assessment of the long-term durability of such concrete structures is of utmost importance and urgently needed as our knowledge on concrete durability beyond the basis of an expected several decade service life is limited. Within its service environment, these structures undergo chemical degradation processes which are very slow but they significantly change the physical integrity and the chemical conditions of the structures with the passage of time. Current issues on durability of these concrete structures include alkali-silica reaction, delayed ettringite formation, leaching, carbonation, etc. which might be magnified under severe/accelerated conditions (high temperature, radiation, moisture, cyclic loading, and acidic environments). These degradations induce an evolution of the microstructure, cracking and changes in transport properties of concrete which are still unclear due to the limited experimental timeframe available to capture these processes. This paper presents an overview on these concerns with the focus on the long-term chemical degradation aspect and presenting a case study on Ca-leaching.

Our world is radically changing. We have will have to mitigate and adapt to the impact of climate change, while supporting a growing population in denser localities, all being vulnerable to increasingly severe climate and weather extremes, with many coastal regions becoming defenseless against global and local sea rise. The area of useable land for habitation and supply infrastructure will diminish as the years continue into the future; this especially being a critical problem for low lying islands, but also for highly developed countries where there exists complex and tightly coupled infrastructure close to sea level. Accepting that nuclear power generation is important for our future, the reality of whether countries can afford the considerable capital cost of providing safe nuclear power is presently questionable. The practice of design for new kinds of nuclear power should apply completely new and innovative thinking that enables lower capital cost, more efficient power generation and highly robust and ultimately resilient civil containment and support structures. Allied design considerations will be reducing the time for carrying out the build and construction process, reduced operating cost, improved through-life operability with less dose risk etc. Of major concern is a new kind of NPP that is efficient, but also robust and resilient in the face of climate change and sea rise.

Further to the climate change summit COP21 organized in Paris, France in December 2015, nearly 200 governments have committed to cut the emission of greenhouse gases and to limit global warming to well below 2 °C by the end of the Century. Nuclear, low-carbon energy, is perfectly integrated within the universal energy mix plan. It is one of best solutions for guaranteeing energy production increases to meet growing demand and protection of the environment. In order to sustainably develop nuclear energy industry, the challenges of new build nuclear power plants (NPP) are to permanently ensure the highest levels of quality, security and safety as well as to optimize the project planning and economy. Therefore, it is important to study and to develop innovative concepts, technologies and methodologies, and to improve the process for the nuclear civil engineering.Based on the simplification and the digitalisation, numerous important measures have been undertaken throughout the design of Hinkley Point C (HPC) NNP in Sumerset, UK. The paper consists of reviewing and analyzing some of them such as: the simplification of structural construction, the balance of use of pre-cast structures, the 3D reinforcement modeling method, the 4D modeling for project management and the improving of design processes. They allow optimizing the design, facilitating the calculations and analysis, and reinforcing the design robustness, anticipating any execution difficulties, minimising the interfaces and reducing the overall design time. A simple, quality and robust design contributes to shorten the construction period, to optimise the time-schedule and to improve the quality, security and safety of the construction as well as significantly reduce the cost and the impacts of construction to the environment. As a result, several perspectives of innovations for the future such as improvement of Building Information Modeling (BIM) applications for the project management will be also introduced.

The purpose of this article is to present the methodology used to define the soil-structure interaction under multiple static loads of a nuclear power plant. Nuclear facilities are characterized by their geometrical complexity and by the large size of the buildings. This has induced the need for robust numerical tools and the need to develop a specific methodology. Actually, in structural calculations the soil is usually represented by linear springs defined at each node of the model by iterative process. When the stiffness computed at two subsequent iterations are almost identical, iteration is stopped. The obtained stiffness values depend on the load case. To simplify this process, and under condition of linearity of the soil behavior, it is proposed to compute the soil flexibility matrix which is finally integrated as a “superelement” within the software ANSYS for the structural computation. The soil flexibility matrix is an intrinsic representation of the soil, which is totally independent from the stiffness, loading, geometry of structures. Then, any modification of structures does not require the reconsideration of the boundary condition (soil). The effectiveness and accuracy of this procedure is discussed with reference to the case study of a nuclear power plant

In rock tunnel construction projects, the big volume of blasted rock muck gives burdens to the cost estimate and the environmental impacts. Tunnel muck recycling is an effort toward the sustainable development when replacing partly a non-renewable resource by a solid waste. In Deo-Ca road tunnel construction project located between Phu-Yen and Tuy-Hoa province (Vietnam), blasted rock was manufactured to become the recycled graded aggregates for constructing the road pavement and the tunnel lining. After recalling some fundamentals of the tunnel muck recycling, the paper introduced the case study on a recycled muck aggregate manufactured from Deo-Ca tunnel excavation. The possibility of utilizing the aggregate for the road base, sub-base and embankment were evaluated through the grain composition analysis. Based on the results of the trial road embankment construction, two mechanical characteristics were examined and the recommended construction parameters were proposed as the prototype for the large scale execution in some segments of the southern approach road of Deo-Ca tunnel.