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International audience; The use of structural adhesive bonding is under development for offshore applications and more specifically for fastener connection to existing steel structures. For this application, creep appears to be one of the main long-term phenomena that needs to be considered during the design approach. To investigate this issue, experimental creep investigations were realised at real scale for two bonded fastener geometries at different stress levels and under different load situations (tension and shear). Local measurements were carried out during these investigations to better describe the long-term behaviour of the bonded fasteners. Despite the non-uniform adhesive thickness in the assembly, numerical investigations have highlighted that the stress field mainly depends on the fastener geometry and the applied load level. This article is dedicated to the description of a methodology that relies on a precise inverse identification of creep parameters and on simplifying hypotheses on the stress field to be able to use simple analytical tools. The methodology enables to identify creep parameters much quicker than a method coupling an optimisation algorithm and a finite element analysis and could easily be used for more complex and precise models.

This study investigates the durability of glass fiber-reinforced polymer (GFRP) reinforcing bars (rebars) and their bond in concrete. Accelerated aging tests were first conducted on bare rebars that were either subjected to direct immersion in an alkaline solution or previously embedded in concrete before immersion in the solution (indirect immersion). Accelerated aging was conducted at different temperatures of the solution (20 °C, 40 °C and 60 °C) and for various periods up to 240 days. Residual tensile properties were determined for rebars subjected to direct immersion and served as input data of a predictive Arrhenius model. A large decrease in the residual tensile strength assigned to the alkali-attack of glass fibers was extrapolated in the long term, suggesting that direct immersion is very severe compared to actual service conditions. Short-beam tests were also performed on rebars conditioned under direct/indirect immersion conditions, but did not reveal any significant evolution of the interlaminar shear strength (ILSS). In a second part, bond tests were performed on pull-out specimens after immersion in the alkaline solution at different temperatures, in order to assess possible changes in the concrete/GFRP bond properties over aging. Results showed antagonistic effects, with an initial increase in bond strength assigned to a confinement effect of the rebar resulting from changes in the concrete properties over aging, followed by a decreasing trend possibly resulting from interfacial degradation. Complementary characterizations by scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and Fourier transform infrared (FTIR) spectroscopy were also carried out to evaluate the effects of aging on the physical/microstructural properties of GFRPs.

One of the aims of applying sustainable development to bridge infrastructure was to provide bridge owners with strengthening solutions that could lead to increased service life for existing structures. In the case of steel bridges, the assessment of the remaining service life is most often linked to the determination of structural deterioration caused by corrosion and fatigue. Damage caused by fatigue is very difficult to assess before crack initiation and is more likely to occur in older structures, where the phenomenon was not taken into account in designs before 1970. In addition, old steel materials display more brittle behavior. To meet these challenges, a preventive methodology for fatigue strengthening of steel structures was developed. The method begins with scheduling a fatigue design analysis of the existing construction to determine the most fatigue damage exposed construction elements of the bridge. The remaining fatigue life of these elements can be increased with a strengthening solution based on the use of adhesively bonded ultra-high modulus (UHM) carbon fiber-reinforced polymer (CFRP) plates, which were applied to a steel surface before failure indicators such as cracks arise. This article presents the development process of this preventive method and a demonstrative application to an existing bridge (Jarama Bridge). Strain measurement was carried out to verify the theoretical expectations of the reinforcement. Different parameters were studied, including the influence of low traffic volumes during the reinforcement application. The results proved the efficiency of this system for the structure under study.

In the framework of sustainable development policies, it is essential that infrastructure owners can rely on effective repair or strengthening solutions, designed and tested in relevance to actual service conditions. In the case of steel structures, fatigue damage is a major concern that can significantly affect the lifespan of the structure, and so far, there are very few operational methods capable of preventing fatigue cracks in the field. Adhesively bonded carbon fiber reinforced polymer (CFRP) composites are being successfully applied to the rehabilitation of concrete structures for more than two decades, and they are currently receiving much interest for the strengthening of steel elements, but mainly for curative purpose after severe damage has occurred. In the present study, which is part of a European project called FASSTbridge, a specific CFRP system has been developed as a preventive method against fatigue damage of steel structures. The proposed system consists of a commercially available ultra-high modulus (UHM) CFRP composite plate compatible with the stiffness of the host steel structures, which is bonded to the steel support using a novel hybrid epoxy/polyurethane adhesive. A first part of the paper presents the main specifications that should be adopted in the design of CFRP strengthening systems applied to steel structures, and that were identified from an extensive literature survey. These specifications have guided the development of the polymer adhesive and the choice of a peculiar commercial CFRP plate in the preliminary phase of the project. Experimental characterizations were then conducted (i) on the formulated hybrid polymer adhesive to optimize its curing schedule and check the previous specifications are fulfilled, and (ii) on CFRP reinforced steel specimens in order to verify the effectiveness of the proposed strengthening system. This experimental program involved both short term and durability tests that were performed by different laboratories. Such an inter-laboratory study made it possible to verify the performances of the developed strengthening system and to assess the influence of installation parameters and environmental conditions. The authors wish to acknowledge Epsilon Composite Company for supporting the study. This work is part of the FASSTBRIDGE project. This project has received funding from the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement no 31109806.0008. FASSTbridge is co-funded by Funding Partners of The ERA-NET Plus Infravation and the European Commission. The Funding Partners of the Infravation 2014 Call are: MINISTERIE VAN INFRASTRUCTUUR EN MILIEU, RIJKSWATERSTAAT, BUNDESMINISTERIUM FÜR VERKEHR, BAU UND STADTENTWICKLUNG, DANISH ROAD DIRECTORATE, STATENS VEGVESEN VEGDIREKTORATET, TRAFIKVERKET – TRV, VEGAGERÐIN, MINISTERE DE L'ECOLOGIE, DU DEVELOPPEMENT DURABLE ET DE L'ENERGIE, CENTRO PARA EL DESARROLLO TECNOLOGICO INDUSTRIAL, ANAS S.p.A., NETIVEI, ISRAEL - NATIONAL TRANSPORT INFRASTRUCTURE COMPANY LTD, FEDERAL HIGHWAY ADMINISTRATION USDOT

This paper reports an experimental study performed to investigate the effectiveness of carbon fiber reinforced polymer (CFRP) laminates in extending fatigue life of old cracked metallic structures. Specimens consist of old metallic plates, mild steel and wrought iron, with one single crack emanating from a rivet hole. This cracking configuration has never been adopted in literature studies and was chosen to be representative of real cracked elements in riveted connections. Two different initial crack lengths before reinforcement, representing two degrees of fatigue damage, were adopted. Four strengthening configurations were investigated including single-sided and double-sided strengthened specimens, Normal Modulus (NM) CFRP plates with or without pre-stressing, and Ultra High Modulus (UHM) CFRP plates. «Beach marking» technique as well as crack gauge were used to monitor and record the crack propagation during fatigue loading. Experimental results show that the application of CFRP plates can effectively reduce the crack growth rate and extend the fatigue life. CFRP plates with high modulus were found to be more efficient. This study represents a contribution to the present state of research and provides some interesting results on crack propagation in CFRP repaired elements close to real riveted ones.

This study focuses on the experimental characterization of the bond behavior between concrete and Fiber Reinforced Polymer (FRP) reinforcing bars (rebars). Pull-out tests were performed on glass, carbon, and aramid FRP rebars, as well as on deformed steel rebars. The influence of various parameters on the bond behavior was studied, such as the type of fibers, the diameter of the FRP bars and their surface geometry. Scanning-Electron-Microscope (SEM) observations were performed to precisely study the sand coating characteristics of these rebars. A main originality of the proposed approach relied on the instrumentation of pull-out samples using Distributed Optical Fiber Sensing (DOFS) instrumentation. Such a distributed measurement system provided access to the longitudinal strain distribution along the rebar near the rebar-concrete interface, and then made it possible to determine the effective development length of the various types of rebars considered in this study. As the introduction of DOFS instrumentation may be intrusive, its influence on the interface behavior was also discussed.

In civil engineering, structural adhesive bonding is increasingly used for the reinforcement or rehabilitation of degraded structures using adhesively bonded composite materials. However, the presence of defects within the bonded joint may affect the effectiveness of the assembly, and their detection is still an issue. The purpose of our study is to evaluate the acousto-ultrasonic (AU) method to detect and identify most common types of defects encountered in adhesively bonded joint and more specifically in FRP reinforced structures. Two types of assembly (made of carbon fibre reinforced polymer pultruded plates bonded on steel or concrete support) were investigated considering three types of defect (voids, kissing-bond defects simulated using a layer of grease at the composite-adhesive interfaces, and weakly polymerized zones implemented through a softer adhesive). The objective of this work is to investigate the ability of acousto-ultrasonic method to detect all those types of defects in the bonded joint with a data-driven methodology. It is expected that the extracted features from the received signals represent the damage state in the joint. For the methodology, a data-driven modelling by means of a Principal Component analysis is performed. Additionally, a Random Forest (RF) is trained using extracted parameters.

This paper investigates the influence of a low elevated temperature on the mechanical behavior of steel B500B rebars and T15.2 prestressing wires in nuclear containment structures. Tensile tests were carried out to evaluate the evolution of mechanical properties during heating. The bond between concrete and rebars was also studied and relaxation tests on prestressing wires have been done. Between 20 °C and 140 °C, the mechanical behavior of rebars and tendons exhibited no major deteriorations. However, a high decrease of the ultimate bond was observed for pull-out tests. Concerning relaxation tests, the temperature tends to significantly increase the relaxation rate.

Nowadays, welding in steel structure design is the most widely used assembly technology. In the case of bridge structures, it has replaced riveting and bolting for the past thirty years. It is well known that this type of structure may deteriorate not just because of corrosion but also because of fatigue issues. In the case of corrosion, specific maintenance actions are currently being undertaken by bridge owners to increase the life span of their structures, such as painting operations. In the case of fatigue issues, it is well known that the high level of residual stresses due to the welding process may increase fatigue hazards. Several techniques may be used to reduce the high level of tensile stresses in the top layer of the weld near the welding toe. In this paper, the influence of welding and shot-peening parameters is investigated. A 3D finite element model is proposed and improved. The model results are compared to the residual stresses measured on several samples using X-ray diffraction method. Effects of the shot diameter, speed and angle impact are investigated. The transverse and longitudinal residual stresses near the welded joint, with a peak tensile stress value of 250 MPa and 280 MPa respectively, drop to a compressive stress value of more than 50 MPa and fit with the experimental results.

In the case of exceptional accidents, nuclear containment structures may be submitted to an internal temperature increase. This may have an influence on the prestressed concrete structures behavior regarding both its mechanical performance and its porosity. The presented study got interested on the impact that a temperature increase may have on the mechanical behavior of the steel reinforcement for both prestressing strands and rebars. In order to remain in realistic situations, it was chosen to study temperatures between 20°C and 140°C. Some experimental investigations regarding the tensile behaviour of steel rebars and their adherence within concrete will first be presented. Then, some investigations on steel strands will be described: some tensile tests at different temperatures, and some relaxation tests to check how the level of prestress loss may be affected by the temperature. This experimental study is part of a national French project (MACENA) aiming at assessing the impact of an accident on the behavior of nuclear containment structures. The gathered experimental data will be used for their damage assessment.

CICE 2018, Conférence internationale sur les composites à matrice polymère renforcée de fibres en génie civil, PARIS, FRANCE, 17-/07/2018 - 19/07/2018; A strengthening system with adhesively bonded CFRP reinforcement was developed in the Infravation project FASSTbridge to extend the remaining fatigue lifetime of existing steel bridge constructions. The premature debonding of CFRP and steel is seen as a major risk to lose the contribution of the retrofitting system. Consequently, an ultrathin debonding sensor to be integrated in the adhesive layer between steel and CFRP was developed as part of the strengthening system. It is suited for continuous monitoring of the integrity of the adhesive joint.The paper explains the underlying physical principles of the sensor and gives insight into the performed tests for the calibration and verification of its functionality. The sensor conception takes the change of a capacitor's electrical impedance as a basis, which occurs when a change in distance between the adjacent conductive faces takes place. It is well assumed that debonding yields separation, which leads to an increase of the monitored impedance. The relationship is explored through single lap sheer experiments and vertical tension bond tests. The sensitivity and the accuracy of the impedance with respect to deformations are revealed by comparing several groups of prototypes with different dielectric layers and viscous materials. The influences of different temperature effects and fatigue loadings are also presented.

International audience; This paper presents a model of prestressing steel relaxation under various levels of loading and temperature. This incremental model enables the delayed strain of prestressing steel wires to be calculated and takes the non-linear coupling of temperature and loading effects into account. It considers different experimental results that could occur in nuclear containment structures, for which a temperature up to 140 °C could be reached for prestressing wires should a loss-of-coolant accident occur. The constitutive law for prestressing steel relaxation is presented, followed by an illustration of the numerical implementation of the proposed model. Finally, the model responses are confronted with experimental results available in the literature supplied by Toumi Ajimi et al. (2017) for the thermo-mechanical conditions between 20 and 140 °C in terms of temperature and 70%–80% of loading ratio.

This study focuses on the modeling of the local bond behavior of Fiber Reinforced Polymer (FRP) reinforcing bars and the surrounding concrete. An analytical bond-slip model is first proposed to describe the interface behavior of the bars embedded in concrete. Then, the parameters of the bond-slip law are identified from experimental data of pull-out tests performed on specimens instrumented with optical fiber sensors. A specific procedure was developed to identify the model parameters. In a second step, the identified analytical law is introduced in a finite element model (cohesive zone damage model) to simulate the pull-out tests, and a complementary model calibration is proposed to account for the non-uniform stress distribution along the interface. Finally, calculated strain profiles at the bar/concrete interface are compared with the experimental profiles measured by optical fiber sensors. The proposed model is found suitable to simulate the bond mechanisms at high load levels, when there is significant interface damage. However, further development of the model is needed to accurately describe the bond stress and slip response at lower load levels and low/moderate interface damage.

International audience; Fastening or reinforcement onto an existing steel structure may create constraints such as the use of hot works (i.e. welding) or loss of weathertightness (i.e. drilling holes and bolting). In order to limit these constraints, there may be a strong interest in using adhesively bonded fasteners. Such a solution requires however strong justification especially regarding long-term properties. This paper presents the results of experimental and numerical investigations realized on the creep behaviour of such bonded fasteners developed for offshore steel structures. Experimental investigations were conducted at room temperature following a precise and repeatable implementation protocol. The results of the various investigations revealed a non-linear evolution of creep displacements according to a Burger law. Numerical modelling has therefore been developed on the basis of Burger's law. A preliminary static study aimed at validating the geometric model and analyzing the initial stress state in the adhesive. The creep study was then carried out to compare numerical results to experimental ones. Although additional investigations are needed, numerically determined creep displacements demonstrated a good consistency with the experimental investigations.

International audience; Bonded composite constructions using timber and ultra-high performance fibre reinforced concrete (UHPFRC) are investigated as highly innovative structural elements technically and economically efficient, and having better environmental performances. Such technique could indeed offer new structures typologies for bridges for instance associating timber for main beams with UHPFRC slabs. In timber-concrete- composite structures, connection is traditionally achieved with mechanical means. The research presented herein describes the timber-concrete assembly by adhesive bonding and specially the behaviour of bonded joint between Laminated Wood (LW) and UHPFRC. This type of assembly has to be investigated concerning mainly the durability of the bonded assembly and its ability to transmit the forces concentrated on edges. The present study describes the development of a test called ''Push-Out'' used to characterize the behaviour of the timber-concrete bonded after or prior to environmental ageing. Following the development of the used test protocol, investigations are realized on four different commercial resins to study the influence of the adhesive stiffness on the force transfer focusing in particular on the failure mode, on the ultimate capacities and some local deformations. The mechanical behaviour of the bonded joint is investigated in particular from a theoretical point of view and from the determination of deformation field obtained by Digital Image Correlation (DIC).

This paper investigates the creep behavior of adhesively bonded concrete/fiber-reinforced polymer (FRP) joints, through experimental and modeling approaches. The first part proposes a methodology for predicting the long-term creep response of the bulk epoxy adhesive; such a procedure consists of (1) performing short-term tensile creep experiments at various temperatures and stress levels, (2) building the creep compliance master curves according to the time–temperature superposition principle in order to assess the long-term evolution for each stress level, and (3) developing a rheological model whose parameters are identified by fitting the previous master curves. In our case, it was found that master curves (and, consequently, parameters of the rheological model) are dependent on the applied stress level, highlighting the nonlinear creep behavior of the bulk epoxy adhesive. Therefore, evolution laws of the model parameters were established to account for this stress dependence. The second part focuses o...

fig., bibliogr.; International audience; The aim of this paper is the enhancement and validation of a layerwise model applied to the analysis of laminates with thin layers of an elastic-plastic adhesive. The thin adhesive layers are modeled as imperfect interfaces across which displacement discontinuities exist. In a previous paper, the constitutive equations of the imperfect interfaces were empirically established without following the layerwise logic. The model equations are revisited and a solid theoretical justification of the new enhanced equations is obtained by making use of the Hellinger-Reissner functional. A theoretical validation of the model is performed by comparing its predictions to those of a solid finite element resolution in the case of a T-peel joint. The results of the enhanced version of the model are very accurate whereas those of the previous version are erratic for the considered joint. As compared to the solid finite element method, an important saving in computational cost is achieved.

In this paper, the durability of the adhesive bond between concrete and carbon fibre reinforced polymers (CFRP) strengthening systems has been investigated under accelerated ageing conditions, i.e. , at 40 °C and 95% relative humidity. Mechanical characterizations were carried-out on control and exposed CFRP strengthened concrete specimens, in order to assess the evolutions of the adhesive bond properties during hydrothermal ageing. Results from different experimental campaigns are presented and reveal significant evolutions (decrease in the adhesive bond strength and/or change in the failure mode) depending on various parameters, such as the surface preparation of concrete, the presence of a carbonated concrete layer, the nature of the CFRP overlay (carbon fibre sheets or pultruded CFRP plates), the ageing behaviour of the bulk epoxy adhesive itself, or the test configuration used to evaluate the adhesive bond strength (pull-off or shear loading test). Moisture diffusion from the superficial layer of concrete ( i.e. , diffusion of interstitial pore solution) towards the adhesive joint is suspected to be a key factor driving the degradation process during hydrothermal ageing.

This study investigates the use of an elasto-plastic adhesive in a bonded double lap joint to increase its ultimate capacity. The first section describes the experimental work we performed to characterize the materials and measure the shear strain along the joint. A comparison between an elastic adhesive and a highly plastic adhesive is made and the effect of the type of behaviour on both the capacity and the characteristic anchorage length is studied. The second section then compares the experimental results with a classical 3D finite element model. Good correlation was found between numerical expectations and experimental measurements, and the modelling allowed us to highlight typical phenomena linked to the use of an elasto-plastic adhesive. In addition, a parameter based on a microscopic measurement has been defined which allows us to describe the onset of plasticity and predict maximum capacity.

The assessment of the structural resistance of historical metal structures involves a depth understanding of many factors, such as the properties of the constructions materials and the structural behaviour of the connection mode. Available information regarding the behaviour of historical riveted connections is quite limited and more information about the residual strain and stress state is still needed in order to allow the preservation of these existing structures. This paper deals with the assessment of stress and strain field which exist around the rivet hole due to the hot riveting process. Experimental specimens were manufactured with riveting technique used in aged metal bridges and different metallic materials for the joined plates were considered. Strain and thermal measurements were done during and after the overall riveting process. The results of the experimental investigation allowed the assessment of the residual strain state and the thermal response of the riveted joint. The experimental results were then used for validation of a 2D axisymmetric model. On the basis of the results obtained, the pre-stress state can be evaluated as well as the stress concentration areas where fatigue cracks may initiate. Thus, the provide findings constitute a supportive tool for further studies regarding the assessment and rehabilitation of historical riveted structures.

The shear strength of concrete/rock interface must be clearly assessed to design the rock foundations. However, the concrete/rock interface has different failure modes which depend on the mechanical characteristics of the materials and the morphology of the rock surface. Consequently, to study thoroughly the shear behavior of concrete/rock interface and to define the cracking mechanisms and debonding propagation along the interface, different instrumentation devices were applied during a large scale direct shear test. A large sample formed by pouring concrete over a large rock surface (shear surface of 1.5 m²), was instrumented using the following techniques: strain gauges, acoustic emission and distributed optical fiber sensor. The different observations made during the test were combined to determine the successive stages of interface failure. The strain gauges, which measure local strains within the materials, showed their ability to detect the crack propagation in the materials and the debonding at the interface. The acoustic emission technique was able to detect the damages in the materials and at their interface. The optical fiber sensor measured strains evolution of the concrete near the interface showing the crack propagation during the test and the progressivedebonding at the interface., Pour la conception de fondation au rocher, la résistance au cisaillement de l'interface béton-roche doit être évaluée. Or cette interface présente différents modes de rupture qui dépendent des caractéristiques mécaniques du matériau et de la morphologie de la surface rocheuse. Différentes instrumentations ont donc été mis en place au cours d'essais de cisaillement à grande échelle afin d'étudier le comportement au cisaillement de l'interface béton roche et de déterminer les mécanismes de fissuration et de décohésion à l'interface. Une éprouvette constituée d'une surface rocheuse de 1.5m² sur laquelle du béton a été coulé, a été instrumentée des dispositifs suivants : jauge de contrainte, capteur d'émission acoustique, fibre optique. Les différentes observations effectuées durant les essais ont été utilisées pour établir les étapes successives de rupture de l'interface. Les jauges qui permettent une mesure locale de la déformation, ont démontré leur leur capacité à détecter la propagation de fissure dans les matériaux, roche et béton et la décohésion à l'interface. L'émission acoustique a permis de détecter l'endommagement des matériaux et à leur interface. La fibre optique a permis de mesurer l'évolution des déformations dans le béton à proximité de l'interface, et en particulier la propagation de fissures et la décohésion progressive à l'interface.

In order that non destructive testing methods become quantitative tools for structure owners, it is needed to assess their precision and sensitivity to the environment. The presented study deals with two electromagnetic methods classically used to survey road pavements and concrete structures: a radar technique and a capacitive technique. The presented investigations aim at assessing the influence of temperature and moisture on the two methods for measurements realized on concrete slabs. The temperature was ranging from 5°C to 45 °C and the surrounding relative humidity (RH) evolved between 60% and 90%. The study is part of a more ambitious topic aiming at defining quantitative non destructive methods to evaluate the water content of concrete structures on site and their state of degradation. The presented work allows assessing the sensitivity of both radar and capacitive techniques to the environmental conditions: temperature and relative humidity. Moreover, the measurement variability of the used capacitive probes with three different sets of electrodes is estimated.

fig., bibliogr.; International audience; In this paper, the layerwise model for laminates with imperfect interfaces and enhanced in Part 1 of this work is confronted with experimental results. The model calculations are validated by comparing its sliding predictions in double lap adhesive joints to the sliding measurements performed in a previous paper. The model predictions agree with the experimental results. Finally, the model is applied to the failure analysis in double lap joints and T-peel joints exhibiting adherend, adhesive and cohesive failures. The model calculations and pertinent failure criteria provide accurate predictions and may become a helpful tool suitable to the design of adhesive joints.

CFRP strengthened concrete specimens were submitted to accelerated ageing conditions (40°C and 95% R.H.) and the time evolution of the adhesive bond strength was monitored using either pull-off or shear loading tests. In a parallel investigation, effects of hydrothermal ageing on the microstructure of the bulk epoxy adhesives were assessed by means of thermal analyses and tensile tests. From those experiments, it was found that the property evolution of the concrete/FRP bonded interface is primarily dependent on the sensitivity of the polymer to ageing conditions, but also on the type of test used for the mechanical characterizations. These trends were supported by numerical modeling based on finite element analysis.

This article is aimed at proposing a new development of a layer-wise 2D finite-element method for multilayers considering the laminated plate as a superposition of Reissner plates coupled by interfacial stresses. Here, despite the 2D description of the laminates, the interfaces show a particular behavior, elastic or elastoplastic (Von-Mises criterion). The finite element formulation is derived and an eight-node multiparticle element is detailed. The application example of a double lap joint with an elastoplastic adhesive is then considered. The adhesive layer is modeled as an interface. The loading scheme is a load-unload-load one. Interface shear and normal stresses are compared to 3D finite element results. A good agreement between both techniques is observed, particularly for the prediction of the history of the slip between the two adherends and the plastic strains in the adhesive.

sous presse; International audience; Structural adhesive bonding is coming into increasing use in civil engineering either for strengthening operations involving the adhesive bonding of external reinforcements or to replace traditional assembly techniques in new structures. However adhesive bonding induces stress concentrations at the edges of the joint, which have been studied by a large number of researchers in order to reduce these phenomena and increase the capacity and service life of the assembly. These studies are all, therefore, concerned with optimizing shear stress transfer in adhesively bonded joints. This paper investigates the role of the hydrostatic pressure on the ultimate capacities of common civil engineering adhesives. This led us to investigate a new joint geometry, the ‘‘curved” bonded joint that naturally creates compressive stresses on the edge of the joint. Initially, classical modelling is conducted to determine how the geometry affects the stresses in the joint. Then, fracture mechanics is used to investigate crack propagation. After this theoretical modelling, several experimental investigations are presented. These are quasi-static tests which compare classical shear lap joints to curved joints. The experimental results are then exploited using the modelling described before. Additional testing is currently in progress, but the curved bonded joint seems to hold good prospects and a patent has been filed.

International audience; Adhesively bonded composite reinforcements are increasingly being used for civil engineering structures. For an adequate use of such a technique, a better knowledge is needed regarding the stress transfer mechanisms involved in polymer joints. This article introduces a single lap shear test for the characterization of the composite-to-concrete or composite-to-steel bonded assemblies. In the first part, an extensive description of the test set-up is given and various methods are proposed to analyse the experimental results. According to Chen's classification (2005) [1], the test under consideration is a near-end supported single-shear test. A first series of tests is reported, that investigates the differences between reinforcement processes based on either pultruded laminates or impregnated carbon fabrics (wet lay-up method), both used for the strengthening of civil infrastructures. The following part discusses the influence of the distance between the extremity of the concrete specimen and the free edge of the adhesive layer. Finally, differences between bonding on concrete and bonding on steel substrates are investigated in a last part. These experimental investigations have allowed us to build-up a considerable body of experience on such usual composite reinforcements, and a large database on this experimental setup and its interpretation

International audience; In this paper, a model of laminated plates called M4-5N and validated in a previous paper is modified in order to take into account interlaminar plasticity by means of displacement discontinuities at the interfaces. These discontinuities are calculated by adapting a 3D plasticity model. In order to compute the model, a Newton–Raphson-like method is employed. In this method, two sub-problems are considered: one is linear and the other is non-linear. In the linear problem the non-linear equations of the model are linearized and the calculations are performed by making use of a finite element software. By iterating the resolution of each sub-problem, one obtains after convergence the solution of the global problem. The model is then applied to the problem of a double lap, adhesively bonded joint subjected to a tensile load. The adhesive layer is modeled by an elastic–plastic interface. The results of the M4-5N model are compared with those of a commercial finite element software. A good agreement between the two computation techniques is obtained and validates the non-linear calculations proposed in this paper. Finally, the numerical tool and a delamination criterion are applied to predict delamination onset in composite laminates.

Building and bridge columns are particularly vulnerable when earthquakes occur. Retrofit of deficient reinforced concrete columns with CFRP jackets and bonded CFRP plates is an efficient method to increase their strength and ductility and then to enhance their seismic resistance. However, issues related to anchorage of the plates can be a concern when strengthening flexural concrete members. This study presents specific end-anchors reinforcement systems which were designed and tested under monotonic and low cycle fatigue loading and compared with a reference system commercially available. A total of 16 specimens were tested up to failure, to check the performances of these anchors. It appears that anchors increase the ultimate capacity and ductility of bonded plates.