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The practice of externally bonded (EB) carbon fiber-reinforced polymer (CFRP) fabrics for structural strengthening increasingly shows evidence of effectiveness for the rehabilitation of existing structures. However, debonding of fiber-reinforced polymer (FRP), particularly in shear, is still a major premature failure mode when using FRP sheets to strengthen concrete structures. This paper presents the results of an experimental investigation of the performance of full-scale reinforced concrete (RC) beams strengthened in shear using EB-FRP U-wrapping (UW) and full wrapping (FW) with different fabric thicknesses. Full wrapping is used mostly on columns with all sides accessible and does not generally apply to beams. The main objectives of this study are to optimize FRP capacity and to evaluate the effect of confinement and the effectiveness of FRP using different strengthening configurations for RC beams, such as FW and UW. The results obtained in this study reveal that fully wrapped beams exhibit enhanced CFRP contribution to shear resistance compared to U-wrapped beams. In addition, the FW configuration eliminated the CFRP debonding failure mode and resulted in an increase in concrete strain. [ABSTRACT FROM AUTHOR]

Coupled shear walls (CSW) are an efficient lateral load-resisting system. Their seismic performance depends primarily on their coupling beams (CBs) ability to provide adequate stiffness and strength. However, many existing buildings with CSW resisting system were designed and constructed according to old codes and standards with insufficient requirements for seismic design. These systems feature unsatisfactory behaviour and prematurely collapse in case of major earthquake events. Therefore, their seismic retrofit is urgently needed. The main objectives of this study are, i) evaluate and compare the seismic performance of CSWs designed to old and new codes; ii) highlight the deficiencies of CSWs designed to old codes; iii) investigate a retrofit method using externally bonded (EB) carbon fibre reinforced polymer (CFRP) composites to enhance the seismic response of deficient CSWs. To that end, a 20-story CSW is considered with different design details including one according to old National Building Code of Canada (NBCC) before the 1970s and the other one designed consistent with the new NBCC 2015 and the Canadian Standard Association, CSA A23.3–14, for Eastern seismic Canadian zone. The nonlinear analyses of CSWs under earthquake records are conducted in two steps. At first, the nonlinear time-history analyses of two types of CSWs are carried out using RUAUMOKO program and the deficiencies of old-designed CSW are identified through the comparison of obtained results. In the second step, the old design CSW is retrofitted using CFRP sheets and reanalysed to investigate the benefits of the retrofit technique in mitigating the shortcomings. The results indicate that CFRP retrofitting is an efficient method to enhance the seismic performance of deficient old CSWs in terms of story displacement, inter-story drift, CBs rotation, and ductility demand. [ABSTRACT FROM AUTHOR]

The use of externally bonded fiber-reinforced polymer (EB-FRP) composites for shear strengthening of reinforced concrete (RC) beams presents many challenges given the complex phenomena that come into play. Premature bond failure, the behavior of the interface layer between FRP composites and the concrete substrate, the complex and brittle nature of shear cracks, and the adverse interaction between internal steel stirrups and EB-FRP are some of these phenomena. Compared to experimental investigations, the finite element (FE) technique provides an accurate, cost-effective, and less time-consuming tool, enabling practicing engineers to perform efficient, accurate nonlinear and dynamic analysis as well as parametric studies on RC beams strengthened with EB-FRP. Since 1996, many numerical studies have been carried out on the response of RC beams strengthened using FRP. However, only a few have been related to RC beams strengthened in shear using EB-FRP composites. In addition, the analytical models that have been reported so far have failed to address and encompass all the factors affecting the contribution of EB-FRP to shear resistance because they have mostly been based on experimental studies with limited scopes. The aim of this paper is to build an extensive database of all the studies using finite element analysis (FEA) carried out on RC beams strengthened in shear with EB-FRP composites and to evaluate their strengths and weaknesses through various studied parameters. [ABSTRACT FROM AUTHOR]

This study presents the results of an experimental investigation on the seismic performance of two reinforced concrete coupling beams (CBs) for coupled shear walls, one with a conventional reinforcement layout designed according to the old National Building Code of Canada (NBCC) 1941 and the other one with a diagonal reinforcement configuration designed according to modern NBCC 2015 and Canadian Standard Association (CSA) A23.3 2014 requirements. Experimental tests were conducted to investigate the behavior of specimens under reversed cyclic loading. The experimental results reveal that the diagonal reinforcement configuration could increase the load-resisting capacity and energy dissipation capacity by 4.4 and 10.2 times, respectively. Moreover, the maximum rate of stiffness degradation decreased from 96% in conventionally reinforced CB to 57% in diagonally reinforced CBs. Furthermore, diagonal reinforcement layout led to more stable hysteretic behavior without considerable pinching. In contrast and as expected, the conventionally reinforced CB did not comply with the requirements of the new design code. Therefore, such CBs should be retrofitted to upgrade their seismic performance in conformity with updated standards requirements. [ABSTRACT FROM AUTHOR]

This paper presents the results of two parametric finite-element studies that were carried out using the PLAXIS-3D finite element (FE) computer code. The following objectives and corresponding parameters were considered: (i) to evaluate the soil pressure on the steel trench box shield; the parameters studied were related to soil type and material, and the study considered till, dry sand, wet sand, and sensitive clay soil; (ii) to assess the effect of trench box material and geometry on earth pressure; the parameters studied were related to trench box material (steel versus aluminum) as well as geometry (plate thickness and strut diameter). These studies included simulation of two steel (or aluminum) trench box shields stacked upon each other to cover the total 6 m (20 ft) deep trench. A Mohr-Coulomb (MC) constitutive material model was chosen for FE analysis (FEA). The FEA results were compared to empirical apparent earth pressure diagrams for a sensitive clay. Comparisons showed that the parameters related to the soil and the trench box have a significant influence on earth pressures. [ABSTRACT FROM AUTHOR]

A finite-element (FE) numerical study using PLAXIS-3D software was carried out to reproduce and validate a full-scale experimental in situ test and to investigate the earth pressure on a flexible temporary trench box shield in soft and sensitive clay soil. The excavation trench model was 6 m (20 ft) deep and was considered as nonlinear and anisotropic clay. A 45 kPa (0.94 ksf) surface overload on top of the soil near the trench box was also simulated to produce a maximum load case on the flexible wall of the shield. Both Mohr-Coulomb (MC) and hardening soil (HS) constitutive soil models were considered for FE analysis. Different values of the modulus reduction factor (MRF) and the coefficient of earth pressure at rest ( K 0 ) were considered to validate the model. For a specific shear strength profile, FE analysis with a linear elastoplastic soil model showed relatively small differences in soil pressure with the field test results along the depth of the trench. Results were also compared with the predictions of well-established analytical formulae. [ABSTRACT FROM AUTHOR]

Highlights • Reinforced concrete (RC) coupled shear walls are often used as a seismic resistance system for medium to high rise buildings. • Old designed RC coupled shear walls do not satisfy the modern design seismic codes' requirements. • Old existing RC coupled shear walls may be at risk and need therefore to be seismically upgraded. • Modern seismic design codes have been found to yield a reliable approximation of design demands. • Externally bonded FRP retrofit improves the seismic behavior of deficient RC coupled shear walls. Abstract When appropriately designed, coupled shear walls (CSWs) are very effective lateral load resisting systems for medium to high rise buildings. They reduce the deformation demands on the building and distribute the inelastic deformation between the coupling beams (CBs) and the wall piers. Their seismic performance depends mainly on the ability of their CBs to provide adequate stiffness and strength. Therefore, the design of the CBs and the walls at their base is of paramount importance. However, many existing buildings with CSWs feature unsatisfactory behaviour under lateral loading as they were designed and constructed according to old codes and standards with insufficient requirements for seismic design. Their seismic retrofit is therefore inevitable. Many conventional retrofit techniques have been attempted in the past to improve the seismic behavior of CSWs. Recently, an innovative technique using externally bonded fibre reinforced polymer (EB-FRP) composite to strengthen existing reinforced concrete (RC) structural elements has emerged. The current study focuses on two objectives related to CSWs: (i) evaluate the seismic performance of old designed CSWs and highlight their deficiencies by comparing its response with that of corresponding modern design CSWs; and (ii) evaluate the effectiveness of EB-Carbon FRP (EB-CFRP) retrofitting on the seismic response of deficient CSWs. To achieve these objectives, two 20-story CSWs located in Western seismic Canadian zone were considered. One CSW was designed according to old National Building Code of Canada (NBCC) 1941 and the other one designed in conformity with modern NBCC 2015 and Canadian Standard Association (CSA) A23.3-14. The nonlinear time-history analyses of the two types of CSWs as well as the CFRP retrofitted one under simulated earthquake motions are carried out using RUAUMOKO program. The observed results confirmed the effectiveness of CFRP retrofitting in enhancing the seismic performance of deficient old CSWs in terms of story displacement, inter-story drift, CBs' rotation, and walls' curvature. [ABSTRACT FROM AUTHOR]

Masonry blocks are usually made of Portland cement and cured by steam. This study explores the possibility of making masonry blocks using steel slag as binder and carbon dioxide as curing activator. By carbonation activation of steel slag blocks, carbon dioxide can be permanently sequestered in steel slag as calcium carbonates, leading to stronger and more durable construction blocks. In this paper, carbonated steel slag paste was first evaluated by thermogravimetry, derivative thermogravimetry, X-ray diffraction, carbon uptake, strength development, and leaching tests. Based on the preliminary results, the full-size masonry blocks were fabricated using steel slag as the binder and granite as the aggregates. The physical properties and durability of full-size steel slag masonry blocks were then examined through their density, water absorption, moisture content, compressive strength, and fire resistance. An economic analysis was performed and a carbon dioxide utilization capacity was estimated. This study demonstrates that production of steel slag masonry blocks by carbonation is an economically feasible way to utilize carbon dioxide. [ABSTRACT FROM AUTHOR]

This paper presents a summary of an experimental investigation and the derivation of a bond-slip model for reinforcing steel embedded in moderately confined concrete under monotonic and cyclic loadings. Moderately confined concrete encompasses the domain between unconfined and well-confined concrete, the limits of which are defined in the paper. The proposed constitutive law adapts and extends the well-known Eligehausen-Filippou model for well-confined concrete to moderately confined concrete. It is described by an envelope curve and degradation rules. The former is obtained through a confinement index, defined in this study as a function of the amount of confining steel and concrete, distance between confining steel and the rebar, and concrete segregation effect. It is proposed to adopt the same degradation rules used for well-confined concrete. These rules are validated through statistical tests for moderately confined concrete. They are found to predict correctly the main features of reduced envelope response under increasing cycling amplitudes but to underestimate response degradation under constant cycling limits for the subsequent cycles to the first cycle. To demonstrate the validity and limitations of the proposed model, its predictions under monotonic loading are compared with experimental results and analytical predictions from other studies. [ABSTRACT FROM AUTHOR]

The objectives of this study are to determine the short-term performance for shallowly buried [2,438 mm (up to 8-ft burial depth)] flexible pipes, evaluate joint performance requirements, and verify AASHTO design assumptions in the light of field test data from in situ measurements. The installation, instrumentation, and field test procedures are presented for high-density polyethylene (HDPE), PVC, and metal pipes under 2D, 1D, and 0.5D burial depths, where D is the pipe diameter. The field test is performed on 914 mm (36 in.) and 1,219 mm (48 in.) pipe diameters. A tandem dump truck is selected for the pipes under 2D burial depth, while the Florida Department of Transportation truck is adopted for the pipes under 0.5D and 1D burial depths. The field test results are presented in terms of the soil pressure distribution around the cross section, as well as the vertical and horizontal pipe diameter changes during construction and under the live load. Special emphasis is given to circumferential wall strains. The validity of the modified Iowa and Meyerhof formulae proposed to predict the horizontal deflection of buried pipes is also investigated. [ABSTRACT FROM AUTHOR]

This study presents the experimental results for seven different tests carried out on high-density polyethylene (HDPE), PVC, and metal pipes with medium-size diameters. The main objective of the experimental program is to evaluate and characterize, under laboratory conditions, the performance and mechanical properties of the various flexible pipes considered in the study. The diameters of the pipes studied are 36 in. (914 mm) and 48 in. (1,219 mm). The laboratory tests conducted are the simple-beam test, parallel-plate test, flattening test, curvedbeam test, joint-integrity test, and tensile test, as well as an environmental stress-cracking test. The results of the tests are presented in terms of load-deflection relations, load versus longitudinal and transverse strains, failure modes, and pipe stiffness. The test results indicate that HDPE and PVC pipes show good performance compared with metal pipes. In addition, the experimental results for flexible pipes meet AASHTO specifications. The HDPE and PVC pipes tested according to the ASTM and AASHTO Standards show pipe stiffness values higher than the minimum specified by the standards. The pipe stiffness values of the HDPE specimens based on the curved-beam test are two to three times greater than those based on the parallel-plate test. It was found that for a given vertical deflection, the HDPE pipe stiffness substantially increased with an increase of loading rate. [ABSTRACT FROM AUTHOR]

Much existing reinforced concrete (RC) civil infrastructure worldwide is in need of shear strengthening and rehabilitation. The use of externally bonded (EB) carbon fiber-reinforced polymer (CFRP) sheets and laminates to strengthen deficient RC beams in shear is now an acceptable and cost-effective practice, particularly under static loads. However, due to its complexity, the cyclic (fatigue) behavior and performance of shear-strengthened beams is not fully documented. Recently, use of CFRP continuous sheets wrapped over the shear length for fatigue upgrade has been studied. This technique may present drawbacks related to surface preparation and FRP debonding. Therefore, when possible, prefabricated CFRP L-shaped laminates can be a cost-effective alternative because they require less surface preparation and do not peel off easily. The objective of this paper was to present the results of an experimental investigation that compared cyclic (fatigue) and static (post-fatigue) behavior of two EB CFRP techniques (sheets vs. laminates) for shear retrofit of RC T-beams. In total, six laboratory tests on full-size 4520-mm-long beams were conducted. The specimens were subjected to fatigue loading of up to 6 million load cycles at a rate of 3 Hz. Specimens that sustained 6 million cycles were then tested monotonically up to failure. The variables examined in the paper were: (1) the EB CFRP strengthening scheme, and (2) the presence and ratio (spacing) of internal shear reinforcement. The test results confirmed the effectiveness of using EB CFRP shear-strengthening methods under cyclic loading. They also revealed that the fatigue performance of RC T-beams strengthened with L-shaped laminates is significantly superior in extending fatigue life compared to corresponding T-beams strengthened with U-wrapped sheets. This was quantified in terms of deflection response (47% increase due to fatigue loading for specimens with L-shaped laminates compared to 90% for specimens with U-wrapped sheets), and the level of increase in steel-stirrups strain range (9–42% vs. 62–114%) and in EB CFRP (36–97% vs. 58–163%). [ABSTRACT FROM PUBLISHER]

The objectives of this study are to evaluate the parameters that affect the behavior of flexible pipes for culverts and storm sewers and to examine the strength-limit states of such pipes proposed by the AASHTO bridge-design specifications. The flexible pipes investigated in the study are high-density polyethylene (HDPE), PVC, and metal pipes. The pipe diameters considered are 914 mm (36 in.) and 1,219 mm (48 in.). A three-dimensional finite-element (FE) model has been developed to simulate the behavior of buried pipes under truck load. Results from field tests conducted by the authors for large-diameter pipes under 2D, 1D, and 0.5D burial depths, where D is the pipe diameter, were used to evaluate the accuracy of the numerical model. Extensive parametric studies were then carried out to examine the effect of burial depth, backfill soil quality, and compaction level on the buried pipes, and their results are reported in this paper. The effect of these parameters has been evaluated in terms of thrust values at the pipe shoulder and springline, vertical diameter changes, and longitudinal strains. Regression analysis was carried out based on the FE model predictions for the first load pass and on results from a research study available in literature to predict the behavior of buried pipes with multiple load passes. The parametric study has shown that the performance of buried pipes varies with the soil type, and the increase of compaction level and soil cover reduces the stresses on buried pipes. The numerical predictions indicate that the provisions of AASHTO bridge-design specifications for HDPE pipes need to be reassessed for very shallow burial depths. [ABSTRACT FROM AUTHOR]

The use of externally bonded carbon fiber-reinforced polymer (EB-CFRP) to strengthen deficient reinforced concrete (RC) beams has gained in popularity and has become a viable and cost-effective method. Fatigue behavior of RC beams strengthened with FRP is a complex issue due to the multiple variables that affect it (applied load range, frequency, number of cycles). Very few research studies have been conducted in shear under cyclic loading. The use of prefabricated CFRP L-shaped laminates (plates) for strengthening RC beams under static loading has proven to be technically feasible and very efficient. This study aimed to examine the fatigue performance of RC T-beams strengthened in shear for increased service load using prefabricated CFRP L-shaped laminates. The investigation involved six laboratory tests performed on full-size 4520 mm-long T-beams. The specimens were subjected to fatigue loading up to six million load cycles at a rate of 3 Hz. Two categories of specimens (unstrengthened and strengthened) and three different transverse-steel reinforcement ratios (Series S0, S1, and S3) were considered. Test results were compared with the upper fatigue limits specified by codes and standards. The specimens that did not fail in fatigue were then subjected to static loading up to failure. The test results confirmed the feasibility of using CFRP L-shaped laminates to extend the service life of RC T-beams subjected to fatigue loading. The overall response was characterized by an accelerated rate of damage accumulation during the early cycles, followed by a stable phase in which the rate slowed significantly. In addition, the strains in the stirrups decreased after the specimens were strengthened with CFRP, despite the higher applied fatigue loading. Moreover, the addition of L-shaped laminates enhanced the shear capacity of the specimens and changed the failure mode from brittle to ductile under static loading. Finally, the presence of transverse steel in strengthened beams resulted in a substantially reduced gain in shear resistance due to CFRP, confirming the existence of an interaction between the transverse steel and the CFRP. [ABSTRACT FROM AUTHOR]

Highlights: [•] Influence of beam size on the shear resistance of RC beams retrofitted in shear with CFRP fabrics is investigated. [•] The contribution of FRP to the shear resistance for beams with no transverse steel is influenced by the beam size effect. [•] The beams with transverse steel appear to be less influenced by the beam size effect. [•] Investigations of the influence of element size on the behavior of the FRP-concrete interface are recommended. [Copyright &y& Elsevier]

Abstract: The main objective of this study is to evaluate the effectiveness of the strut-and-tie method (STM) in predicting the capacity of shear-strengthened large-scale beams with externally bonded (EB) and carbon fibre reinforced polymers (CFRPs). The STM approach is validated with 14 specimens shear-strengthened with a U-wrap scheme. The test specimens are grouped into four series on the basis of the spacing between their steel stirrups: 140, 203, 406 and 610mm. Each series of girders includes a control specimen, with no external CFRP for shear strengthening, and specimens strengthened with one, two, and for the second and fourth series, three layers of CFRP. A practical analysis and detailed design for the CFRP shear-strengthened girders using the STM is presented. In the method, externally bonded CFRP strips on a CFRP shear-strengthened RC member can act as additional tension ties. The tensile forces in the steel stirrups and the CFRP laminates are combined according to a proposed equation. The results obtained using the STM are compared with the experimental results as well as the Canadian Bridge Design code (CSA-S6-06). The STM analysis approach, without considering the safety factor proposed by the ACI, shows its capability to predict the loading capacities of FRP shear-strengthened large-scale beams with good accuracy. [Copyright &y& Elsevier]

The embedded through-section (ETS) technique was recently developed to avoid the debonding failure that occurs with other fiber-reinforced polymer (FRP) strengthening techniques such as the externally bonded (EB) and near-surface-mounted (NSM) methods. The method offers greater confinement and leads therefore to a substantial improvement in bond performance. In addition, it requires less concrete preparation than the other strengthening techniques. In this study, experimental results from 13 direct-shear test specimens are reported. The influence of the following major parameters on the bond behaviour of FRP-strengthened reinforced concrete beams is examined: concrete strength, hole diameter, bar diameter, bar surface area, and bar bond length. The experimental results show that debonding can be avoided by providing a sufficient bar length and high concrete strength. Among the analytical models suggested in the literature for the bond behaviour of FRP reinforced concrete, the BPE modified model and the CMR model are compared with the experimental results obtained here. The CMR model with new fitting parameters is found to be an accurate way of simulating the experimental results. [ABSTRACT FROM AUTHOR]

Abstract: The embedded through-section (ETS) strengthening method is a promising technique recently developed to increase the shear strength of deficient reinforced concrete (RC) beams. The method uses an adhesive to bond fiber-reinforced polymer (FRP) bars embedded through pre-drilled holes into the concrete core. The motivation for this work is the fact that a full understanding of the ETS technique can be achieved through finite element models. Two-dimensional finite element models have been developed to address the CFRP bar/concrete interfacial behavior of the ETS pull-out test. In the model, discrete truss elements are oriented above and below the CFRP bar to connect the bar to the two sides of the concrete. The Cosenza–Manfredi–Realfonzo (CMR) bond stress–slip model is used to represent the bond behavior. Numerical predictions show that the CFRP bar/concrete interfacial profiles are useful in determining the optimum lengths of the CFRP bars. The study has been extended to investigate FRP shear-strengthened beams using the ETS method by developing a three-dimensional finite element model. Nonlinear material behavior of the plain concrete, steel reinforcing bars and CFRP bars has been simulated using appropriate constitutive models. Results are presented in terms of ultimate load-carrying capacities, load–deflection relationships, and axial strains in the CFRP bars. The numerical predictions are compared with experimental data, and very good agreement is obtained. [Copyright &y& Elsevier]

The National Building Code of Canada (NBCC) takes into account the effect caused by the higher order vibration modes using the dynamic amplification factor Mv. This factor depends on the types of systems used to resist seismic forces. However, for load-bearing partitions, the NBCC recommends using the Mv that pertains to moment-resisting structures when the level of coupling, DC ≥ 2/3 (coupled load-bearing partition system) or the Mv pertaining to walls and structure-wall systems when DC < 2/3 (partially coupled load-bearing wall system). Consequently, the NBCC connotes a fundamentally different dynamic behaviour than these two load-bearing wall systems, even when the deviation of the respective DC on either side of the DC = 2/3 value is low. This deviation was the basis behind the present study to assess the effect caused by the higher order vibration modes in coupled and partially coupled load-bearing walls, and to propose an Mv factor specific to these important structural systems. The numerical investigations of this study analyse a large array of load-bearing wall systems and take into account the following parameters: ( i) three building heights (10, 20, and 30 storeys), ( ii) two levels of coupling (DC = 0.6 and DC = 0.7), ( iii) five soil classes (A to E), and ( iv) two cities, Montreal and Vancouver, representative of the seismic risk zones for Eastern and Western Canada. [Journal translation] [ABSTRACT FROM AUTHOR]

This article deals with the shear strengthening of reinforced concrete (RC) beams using externally bonded fibre-reinforced polymers (FRP). The requirements for shear strengthening of RC beams in CSA (Canadian Standards Association) S806-02 code are summarized and compared to other existing international codes. Moreover, a comprehensive analysis on major parameters influencing on shear contribution of FRP in relation with the current equations of the Canadian codes and other standards is represented in this article. Based on the mentioned analysis and recent achievements a new, rational and evolutionary predicting model to calculate the effective strain and the shear contribution of FRP is proposed. The new model takes into account the major parameters such as, the effect of transverse steel reinforcement. This model will ultimately be used in CSA S806-02. [ABSTRACT FROM AUTHOR]

This paper presents results from an experimental investigation of the bond-slip performance of moderately confined concrete under monotonic and cyclic loading. The effects of six factors on the bond-slip response and on the bond mechanisms are investigated. These factors are grouped into two categories: the first category of four factors is related to the confining conditions, the second category to the loading conditions. A total of 43 pullout tests under monotonic and cyclic loadings were performed. Results show that the quantity of confining steel and the distance between the tested bar and the confining steel are the most important factors affecting the overall bond response. Bar spacing and height of concrete cast below the bar have less significant effects on the overall response, affecting mainly the initial response phase. The height of concrete cast below the tested bar is found to affect the maximum bond resistance to the same extent as in well-confined concrete. Cyclic bond behaviour of moderately confined concrete is found to be similar in shape and in cyclic degradation to that of well-confined concrete. It was also found that most of the bond response parameters, such as maximum bond resistance and the post-peak (softening) phase, can be predicted with excellent accuracy in terms of the factors investigated. Cet article présente les résultats d'une étude expérimentale du comportement adhérence-glissement du béton modérément confiné sous chargement monotone et cyclique. Six facteurs influençant la réponse adhérence-glissement et sur les mécanismes d'adhérence sont étudiés. Ces facteurs sont regroupés en deux catégories : la première catégorie comporte quatre facteurs et est reliée aux conditions de confinement et la deuxième catégorie, aux conditions de chargement. Au total, 43 essais d'arrachement ont été réalisés sous chargement monotone et cyclique. Les résultats montrent que le comportement de l'adhérence est essentiellement affecté par la quantité de l'acier de confinement et la distance entre la barre mise à l'essai et l'acier de confinement. Les effets de l'espacement des barres d'armature et de la ségrégation du béton sur le comportement de l'adhérence sont de moindre importance et affectent principalement la phase initiale de la réponse adhérence-glissement. L'effet de la ségrégation du béton affecte la résistance maximale de l'adhérence au même titre que dans le béton bien confiné. Le comportement cyclique de l'adhérence d'un béton modérément confiné est similaire en forme et en dégradation cyclique à celui d'un béton bien confiné. Par ailleurs, la plupart des paramètres de la réponse adhérence-glissement, tels que la résistance maximale d'adhérence et la phase post-pic (écrouissage), peuvent être prédits avec une excellente précision en termes des facteurs étudiés. [ABSTRACT FROM AUTHOR]

New technologies based on seismic isolation are gaining popularity among engineers given the savings on construction costs. The long-term advantage of these technologies preserve the serviceability of the structure after an earthquake and eliminate the cost of reconstruction. This advantage is critical for 'emergency' bridges, required to remain operational after an earthquake. The present article examines a method of isolating the foundation of existing bridges as part of a seismic retrofitting effort. This approach is supported by the increasing interest in this method, especially since its adoption by the Canadian standards and due to the fact that engineers are not too familiar with non-linear dynamic design methods. Another source of motivation is the opportunity to apply this technique to the refection of a few Quebec bridges. The steps of the antiseismic calculations as well as the results of non-linear analyses pertaining to the Madrid Bridge are presented and discussed. This paper may become a useful tool for engineers and their projects of retrofitting existing bridges. Les nouvelles technologies basées sur l'isolation sismique connaissent un intérêt grandissant parmi les ingénieurs, compte tenu de l'économie sur le coût de la construction de l'ouvrage qu'elles offrent. Elles présentent également un avantage indéniable à long terme étant donné qu'elles préservent la fonctionnalité de l'ouvrage après séisme et éliminent le coût de reconstruction. Cet avantage revêt une importance capitale pour les ponts dits de secours qui doivent demeurer en service après le séisme. Cet article présente une méthodologie relative à l'isolation de la base des ponts existants dans un contexte de mise en conformité sismique. Cette démarche est motivée par l'intérêt grandissant de cette méthode, notamment depuis son adoption par la norme canadienne d'une part et d'autre part par le fait que les ingénieurs praticiens sont moins familiers avec les méthodes dynamiques non linéaires de conception. L'opportunité offerte aux auteurs de mettre en application cette technique pour la réfection de quelques ponts au Québec est une autre source de motivation. Les étapes de calcul parasismiques sont pourvues, et les résultats des analyses non linéaires relatives au pont Madrid sont présentés et discutés. L'article est destiné aux ingénieurs praticiens qui y trouveront un outil utile pour leurs projets en réhabilitation de ponts existants. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive review of the new provisions for the design of coupled shear walls in Canadian seismic zones. It follows major revisions that were incorporated in the National Building Code of Canada 2005 (NBCC 2005) and in the Canadian standard Design of concrete structures (CSA A23.3-04), which were due, in particular, to the adoption of a new Canadian map of seismic risk. The present study is intended to address recurring confusions in current practice and the difficulties expressed in the application and interpretation of the new NBCC 2005 and CSA A23.3-04 provisions. A design flowchart is thus proposed as a practical guide, describing, step by step, the required verifications at each stage of coupled shear walls calculation. Finally, to demonstrate the applicability of these new provisions, a numerical example is detailed, following the presented design flowchart. [ABSTRACT FROM AUTHOR]

This paper presents results of an experimental investigation on the fatigue performance of the welded multiple support bar modular bridge expansion joint (MBEJ) used for the recent Jacques Cartier Bridge rehabilitation in Montreal. Three identical subassemblies of the modular joint system were tested in fatigue. Both vertical and horizontal load ranges were applied to the test specimen simultaneously in the following proportions: (i) vertical load range = ΔPv and (ii) horizontal load range = 0.2ΔPv. Different loading ranges were applied to each specimen giving a sufficient number of points to define the experimental fatigue stress range versus the number of cycles (S–N) curve. The number of cycles varied between 567 900 and 3 600 000, while the calculated stress range within the welded connection details varied between 81.4 and 166.7 MPa. Static calibration tests were performed prior to the fatigue testing of each specimen. These calibration tests confirmed the validity of the structural three-dimensional analytical models and also established the repeatability of the experimental data, in conformity with the requirements of the NCHRP-402 report. Fatigue cracks of the same type as those reported by the NCHRP-402 report were observed within the welded connection detail. No fatigue cracks were observed elsewhere. The experimental fatigue curve of the welded connection showed that the fatigue resistance of the welded MBEJ is compatible with category C and C' details, as defined by the AASHTO LRFD 1998 bridge design code. This paper is very useful, as it demonstrates the applicability of the complex requirements of the NCHRP-402 report. These requirements are increasingly gaining wide acceptance among bridge engineers and bridge owners. [ABSTRACT FROM AUTHOR]

This paper describes the procedure and results of the field tests on high-density polyethylene (HDPE), PVC, and metal large diameter pipes subjected to a highway design truck loading. Numerical simulations using finite element method are performed to determine pipe-soil system response under live load application. Comparisons of field test data with the predicted responses are made for soil pressures around and above the pipes, deformed cross-sectional pipe profiles, and pipe deflections. The field test results indicated that the buried flexible pipes, embedded with highly compacted graded sand with silt, demonstrated good performance without exhibiting any visible joint opening or structural distress. Under shallow burial conditions, the AASHTO specified deflection limit of 5% is found to be adequate for installation of the flexible pipes during the construction phase, and a vertical deflection limit of 2% is suggested for HDPE pipes based on the truck load response and repeated loading effect. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents results of an experimental investigation involving twelve tests on 3000mm-long reinforced concrete (RC) T-beams strengthened in shear with externally bonded carbon fiber reinforced polymer (CFRP) composites. The main objective of this study was to evaluate the effect of the following parameters on the shear performance of strengthened RC beams: (i) the CFRP ratio, (ii) the transverse steel reinforcement ratio, and (iii) the type of beams (deep versus slender). The results clearly indicated the existence of an interaction between the internal transverse steel reinforcement and the externally applied CFRP in terms of the gain in the shear capacity as well as of the strains. Results also showed the influence of the type of beam on the load capacity gain due to the CFRP. Finally, comparison of the shear resistance values as recommended by the fib TG9.3 (2001), ACI-440R (2002), and CSA S806-02 (2002) guidelines, with the test results clearly indicated that guidelines fail to capture the influence of the studied parameters. [Copyright &y& Elsevier]

This paper presents results of an investigation on the shear strengthening of reinforced concrete (RC) beams with externally applied fibre reinforced polymer (FRP) composites. The first part of the study reviews and synthesizes the state of the art in the subject. Also, the requirements and recommendations specified in the Canadian CSA S806-02 standards, the American ACI-440 guidelines, as well as the European fib TG9.3 recommendations are compared with the test results reported in the literature so far. This part of the study indicates that the major parameters involved in the behaviour of RC beams strengthened in shear with FRP were not fully investigated. This can explain the observed discrepancies between the resistance values predicted by the codes and guidelines, and those obtained by tests. This has been the main impetus to carry out an experimental investigation, which is the subject of the second part of this paper. The objective of this experimental investigation was to study the influence of the following parameters on the performance of RC beams strengthened in shear with FRP composites: (i) the FRP ratio, (ii) the transverse steel reinforcement ratio, and (iii) the type of beam (deep versus slender). Results clearly showed the interaction between the FRP composite and the internal transverse steel reinforcement in the shear resistance mechanism. Results also showed the influence of the type of beam on the gain due to FRP on the carrying capacity of the beam. [ABSTRACT FROM AUTHOR]

• Cave-ins are still frequent in the construction industry and present a serious risk for workers. • A comparison of jurisdictions and construction guidelines is presented. • A review of recent research work on cave-in risks with finite element analyses is presented. • Based on those, research needs for sensitive clay cave-in risks are proposed. Cave-ins are very frequent in the construction industry and present a very serious risk for workers who operate inside trenches or excavations. Studies show that excavations or trenches in Quebec sensitive clay soils are extremely hazardous due to possible severe and sudden loss of soil shear strength. Many North American and European construction safety authorities have already adopted proper methods and excavation protection practices according to their soil classification. This paper reviews existing construction codes and guidelines, as well as published research studies related to worker safety and protection in excavations and trenches in sensitive clay soil. The paper also discusses the needs for research on prevention strategies to eliminate potential cave-in risk sources from occurring in Quebec sensitive clay soil. [ABSTRACT FROM AUTHOR]

This paper deals with the shear strengthening of reinforced concrete (RC) beams using externally bonded fiber-reinforced polymer (EB FRP) composite materials. The first part of the paper reviews the evolution of North American codes and standards for the shear resistance of RC beams strengthened with EB FRP composites, whereas the second part provides a comprehensive analysis of the major parameters influencing the contribution of FRP to shear resistance. It also presents a comparison of the predictions of current design standards (ACI 440.2R 2017; CSA/S6 2019; CSA/S806 2012; fib -TG9.3 2001) with the results of experimental tests reported in the literature. The study shows that major parameters influencing the shear behaviour have received little attention. These parameters include in particular: (i) the presence and ratio of internal transverse steel reinforcement and (ii) the number of EB FRP plies (layers). This may explain the observed discrepancies between the prediction models of existing equations for shear resistance and the results obtained from tests. Consequently, a database extracted from the experimental studies was developed as part of this study. The results obtained highlight and confirm the existence of an interaction between the EB FRP composites and the internal transverse steel reinforcement with regard to shear resistance of RC beams. They also show the existence of an optimal FRP stiffness beyond which there is no substantial gain in resistance attributed to the EB FRP. [ABSTRACT FROM AUTHOR]

A large number of existing buildings have seismic-resistant systems designed according to old code provisions. These structural systems exhibit non-ductile behavior and can present a significant risk in the case of a moderate or significant seismic event. Reinforced concrete–coupled shear walls designed to old codes and standards are among those deficient structures that need to be seismically upgraded. This article aims to investigate a new retrofitting and upgrading method using externally bonded carbon fiber–reinforced polymer composites for existing or/and damaged reinforced concrete coupling beams that can improve the seismic performance of them during earthquakes. To this end, an experimental test was conducted to evaluate the seismic behavior of two identical reinforced concrete–coupled shear wall specimens under reverse cyclic loading. To simulate the old existing building, the specimens were designed and constructed according to the old 1941 National Building Code of Canada with a conventionally reinforced coupling beam. One of the specimens was tested as a control, and the other was strengthened using externally bonded carbon fiber–reinforced polymer composites to evaluate the improvement in its seismic performance. Results show that the retrofit using externally bonded carbon fiber–reinforced polymer resulted in significant enhancement in strength and energy dissipation capacity compared to the conventionally reinforced coupling beam from the control specimen. In addition, externally bonded carbon fiber–reinforced polymer sheets resulted in much improved hysteretic and ductile behavior and in lesser strength and stiffness degradation. [ABSTRACT FROM AUTHOR]

Highlights • Shear strength of circular RC members with hoops. • Shear strength of circular RC members with spirals. • Codes, design guidelines were assessed. • FRP hoops' and spirals' shear contribution of RC member were assessed. • Proposed a new shear design equations, for hoop and spiral. Abstract Nowadays, design guidelines and codes contain valuable shear provisions for the design of concrete bridge members reinforced with fiber-reinforced-polymer (FRP) bars. Limited researches seem to have assessed the shear strength of circular concrete members reinforced with FRP reinforcement. Therefore, these standards do not provide specific formulae for circular RC members designed with FRP bars, hoops and spirals under shear loads. This paper reports experimental data about the shear strength of circular concrete specimens reinforced with FRP bars, discrete hoops and continuous spirals. Full-scale circular concrete specimens with a total length of 3,000 mm and 508 mm in diameter were constructed and tested up to failure. The test parameters included the type of reinforcement (glass FRP and carbon FRP versus steel) and configuration of the shear reinforcement (discrete hoops versus continuous spirals). The investigation revealed that the specimen reinforced with FRP hoops exhibited high load-carrying capacity comparable to the counterpart reinforced with FRP spirals. The experimental shear strengths of the FRP-reinforced concrete specimens were compared to theoretical predictions provided by current codes, design guidelines. The results of this study can be used as a fundamental step toward code provisions for using GFRP or CFRP spirals and hoops as internal shear reinforcement. [ABSTRACT FROM AUTHOR]

The objective of this paper is to evaluate the bond performance of different anchorage techniques that can in particular be used for fiber reinforced polymers (FRP) shear-strengthened reinforced concrete (RC) T-beams. The results of two different experimental programs are gathered and compared to highlight some common aspects. Overall, 25 bond tests on FRP-to-concrete joints with test setups that simulate the behavior of an anchored FRP shear-strengthened beam are examined. The anchorage techniques considered are mechanical anchors, FRP bars, longitudinal FRP plates, extensions to the underside of the flange, and carbon FRP (CFRP) ropes. The influence of concrete strength, plate width, bond length, and rope length on bond strength is investigated. Experimental results show that both bond strength and ductility are affected by the anchorage technique used. In light of the experimentally observed failure modes, some bond strength models provided in the literature and design standards are used to predict the maximum bond load of FRP-to-concrete joints and compared with experimental results. [ABSTRACT FROM AUTHOR]

Carbon fiber-reinforced polymer (CFRP) rope was recently developed to anchor fiber-reinforced polymers (FRP) shear-strengthened beams that conventionally uses U-wrap scheme. The rope is a bundle of flexible CFRP strands held together by a thin tissue net. In this technique, holes are drilled through the web at the web-flange intersection, and CFRP ropes are inserted through the holes and flared onto the two free ends of the U-wrap scheme. The technique offers substantial improvements in bond strength and ductility because it converts the U-wrap scheme similar to a full-wrap scheme. The objective of this paper was to investigate the bond behavior of CFRP L-strip plates anchored with CFRP ropes. The experimental program consisted of 16 tests on FRP-to-concrete joints, of which six were unanchored (control specimens) and 10 were anchored by CFRP ropes. The influence of concrete strength, rope length, and plate width on bond behavior was examined. Experimental results showed that the bond performance greatly improved with increasing FRP plate width and rope length, but concrete strength had a negligible effect, which is attributed to high thickness and narrow width of CFRP L-strips used. Theoretical formulations provided to account for the ultimate bond load were compared with the experimental results, and a modification factor to estimate the effect of the presence of CFRP rope was suggested. [ABSTRACT FROM AUTHOR]

Recent years have seen valuable research work and widespread applications of fiber-reinforced polymer (FRP) bars as flexural and shear reinforcement for concrete structures. Nonetheless, the axial compression behavior of FRP reinforced concrete (RC) columns has not yet been defined. This study introduces equations and a confinement model to predict the stress-strain envelope responses of RC columns reinforced with carbon-FRP bars (CFRP) and confined by CFRP spirals or hoops. The model takes into account the effect of many parameters such as transverse reinforcement configuration, longitudinal reinforcement ratio, volumetric ratio, and the size and spacing of spirals or hoops. Results of analysis using the proposed confinement model were verified by means of a series of experiments with full-scale circular CFRP-RC columns. The proposed equations have been shown to predict accurately confined concrete core stress, corresponding concrete strain, and prepeak and postpeak stress-strain relationships for the tested CFRP-RC column specimens. [ABSTRACT FROM AUTHOR]

Several anchorage techniques have been proposed in the literature to delay or prevent the debonding failure mode and to upgrade and restore the capacity of externally bonded (EB) fiber-reinforced polymers (FRPs) shear-strengthened beams in a U-wrapping scheme, such as NSM, FRP extension, FRP insertion, horizontal FRP, FRP patch, FRP rope, FRP spike, metallic anchors, and combined anchors. Although the advantages of these anchorage techniques have been acknowledged by researchers, their effectiveness in enhancing FRP shear contribution is controversial. The present study is a state-of-the-art review of experimental tests that were carried out to investigate the effectiveness of anchorage techniques for FRP shear-strengthened beams. The various anchorage techniques are evaluated in terms of FRP shear strength and FRP strain based on the parameters that have a major influence on the behavior of FRP shear-strengthened beams. Furthermore, strength models for FRP shear-strengthened beams provided in various design guidelines are used to predict FRP shear strength compared to experimental results. The significance of the present findings with respect to FRP shear contribution is discussed. [ABSTRACT FROM AUTHOR]

Abstract Basalt-fiber-reinforced polymer (BFRP) bars are expected to provide benefits that are comparable or superior to other types of FRP while being significantly cost-effective. However, extensive investigations are needed to evaluate the long-term characteristics and durability performance of these bars. This article presents an experimental study that investigated the physical, mechanical, microstructural, and durability characteristics of newly developed basalt-fiber-reinforced polymer (BFRP) bars. The physical, mechanical properties and microstructural characteristics were evaluated first on the unconditioned BFRP bars. The durability performance of the BFRP bars was then assessed by conducting the mechanical tests, such as transverse-shear test, flexural test, and interlaminar-shear test, on the specimens after different exposure periods (1000; 3000; and 5000 h) at 60 °C. Thereafter, the BFRP bar properties were assessed and compared with the values obtained on the unconditioned specimens. The test parameter was conditioning time (1000; 3000; and 5000 h). The test results revealed that the unconditioned BFRP bars had the best physical properties. On the other hand, the long-term durability performance revealed that the transverse shear-strength, flexural-strength, and interlaminar shear-strength retention were decreased by 12%, 19%, and 21%, respectively. Highlights • The study assessing the durability of BFRP bars when exposed to harsh environments. • Assessing the effects of aggressive environmental on mechanical strength of the tested specimens. • Physical Properties and SEM analysis were used to assess the degradation of BFRP bars. • Long-term predications of the BFRP bars according to Arrhenius and fib Bulletin 40 were estimated. [ABSTRACT FROM AUTHOR]

Abstract: Numerical analyses are performed with the ADINA finite element (FE) package to predict the behavior of beams shear-strengthened using externally bonded (EB) fiber reinforced polymers (FRPs). Nonlinear material behavior of the plain concrete, steel reinforcing bars, FRP composites and FRP/concrete interface are simulated with appropriate constitutive models. In the FE analysis, the use of truss elements versus shell elements to simulate the behavior of the FRP composites is evaluated. The influence of three types of interface element to represent the FRP/concrete interfacial behavior is examined. These elements are spring elements, discrete truss elements and continuous truss elements. The appropriate interface element is selected on the basis of the best fit of numerical predictions obtained for a predetermined set of experimental data. In order to investigate the influence of including horizontal interface elements, the interfacial response is provided parallel and perpendicular to the fiber orientation to examine the horizontal component of the principal diagonal-tension stresses. It is shown that the approach identified to represent the FRPs and the FRP/concrete interfacial behavior can significantly influence the numerical predictions of FRP shear-strengthened beams. [Copyright &y& Elsevier]