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In this study, behaviors of reinforced concrete beams manufactured from several concrete types are experimentally and numerically investigated under dynamic impact loading. In the experimental part of the study, 12 beams manufactured using low strength concrete, normal strength concrete and engineered cementitious composites (ECC) containing polyvinyl alcohol (PVA) fibers are tested under dynamic impact loading. The dimensions of the manufactured reinforced concrete beams are also used as a variable to observe the effect of beam size on the behavior under dynamic impact loading. After the experimental study, finite element analyses of the tested beams are also conducted by using commonly used finite element software to observe the stress distribution under the impact loading. The results obtained from the experimental study illustrated that material type significantly affected the width of the observed cracks on the test specimens. Generally the smallest cracks formed on the test specimens manufactured using ECC and the largest cracks formed on the test specimens manufactured using low strength concrete. The results of the finite element study showed that the crack patterns on the test specimens are in good agreement with the stress distributions obtained from the impact loading simulations. [ABSTRACT FROM AUTHOR]

In this study, strain distributions and the bond slip behaviors at the carbon fiber reinforced polymer (CFRP) strips and reinforced concrete interface were investigated. 14 concrete specimens with externally bonded CFRP strips were tested. Main variables considered in the experimental study were width of the CFRP strips, bond length of CFRP strips and the number of anchorages. The test results obtained from the experimental study are comparatively presented in terms of strain distributions on CFRP strips with anchorages, stress – displacement behaviors, initial stiffnesses, energy dissipation capacities of test specimens. From the test results it is observed that using anchorages is very effective in terms of ultimate load capacity, strain distribution and energy dissipation capacity. The results of the experimental study are compared with analytical results obtained from several bond strength models available in the literature. A bond slip model was proposed based on the results of the conducted tests. It was observed that bond stress of the CFRP strips increased with increasing number of anchorages. [ABSTRACT FROM AUTHOR]

Hysteretic responses of timber framed shear walls are experimentally investigated in this study. The variables considered in the study are presence of openings with varying dimensions, presence of horizontal retrofitting elements and aspect ratios of timber framed shear walls. The data obtained from the tests conducted on timber framed shear walls are used to deduce conclusions about the behavior of such type panels in terms of load–displacement relationships, strengths, stiffnesses, displacement ductilities, energy dissipation capacities and failure modes. Furthermore, the ultimate loads resisted by the timber framed shear walls are also calculated as per Eurocode 5. Then the analytical and experimental results are comparatively presented. From the test results, it is observed that the aspect ratio of a timber framed shear wall is a significant factor on the load–displacement relationship and failure mode. The varying dimensions of openings on the timber framed shear walls significantly affect the strength and stiffness of the panels. The increasing opening dimensions reduced the strength and stiffness values of the panels. Besides, from the comparison of analytical and experimental results, it is observed that the analytical results are not in good agreement with the experimental results. [ABSTRACT FROM AUTHOR]

This research study is aimed at evaluating the effects of carbon fiber reinforced polymer (CFRP) strengthening on the punching shear behavior of two-way reinforced concrete (RC) slabs strengthened with CFRP strips having openings varying in size and location. In the scope of the research study, series of experiments are conducted on eight test specimens of CFRP strengthened two-way square RC slabs having openings with variable locations and sizes. In the experimental study, the specimens (with dimensions of 2000 × 2000 × 120 mm) are tested by applying an axial load from the top of a square column (200 mm × 200 mm) located at the center of the test specimen. Each test specimen has one opening with the dimensions of 300 × 300 mm or 500 × 500 mm located adjacent or 300 mm far from the central column in a parallel or diagonal position. The test specimens are strengthened with four CFRP strips (150 mm wide) located under the slab next to the opening of the specimen. Additionally eight U shaped CFRP strips (150 mm wide) located at the corners of the opening are used to further retrofit the test specimens. The effects CFRP strengthening and varying size and location of openings on the punching shear behavior of the test specimens are considered by examining the slabs’ bearing capacities and stiffnesses obtained from the results of the experiments in comparison to the results of a former experimental study. Furthermore, the experimental results obtained from the study are used to evaluate the accuracy of the available code equations to predict the punching shear capacity of flat slabs. From the comparison, it is observed that the punching shear capacities of the retrofitted test specimens significantly increased with respect to the punching shear capacities of the bare specimens with opening tested in a former study. Moreover, it is also observed that the several equations proposed by structural codes underestimate the punching shear capacities of the test specimens. [ABSTRACT FROM AUTHOR]

Studies focused on the effects of supporting conditions on the behavior of reinforced concrete slabs subjected to static and dynamic loadings may be found in the literature. However, in the literature no study was found about the effect of variation of the support conditions on the behavior of slabs subjected to impact loads. Consequently, an experimental study was performed on the behavior of reinforced concrete slabs subjected to impact loading. Eight (8) square reinforced concrete slabs with dimensions 500 × 500 × 50 mm were tested by changing two parameters; (i) support type, (ii) support layout. In scope of the experimental study, 4 different support layouts were considered on 2 main support types (i.e. fixed and hinge supports). In the experimental study, impact loadings were applied to the specimens using a drop weight impact test set up. Acceleration-time responses of those specimens were measured by dropping a standard-weighing hammer from a height of 500 mm. Effects of the parameters on the damage distribution, number of drops, acceleration-time, velocity-time and displacement-time responses were investigated. Variations of velocities and displacements were calculated for all specimens by using measured accelerations. Finite element analyses conducted using ANSYS Explicit STR software was used to simulate the experiments. It was observed that the results obtained using the numerical model was in good agreement with those obtained from the experimental study. [ABSTRACT FROM AUTHOR]

In scope of this study performances of protective layers, proposed to protect the pipes from sudden impact loads such as rock falls, are aimed to be compared. In this study, performance, strength and energy absorption capability of geofoam structures against impact forces are investigated by using drop weight impact testing apparatus. Pipes that are manufactured from steel and composite materials are tested with only 130 mm thick sand protecting layer without any geofoam structure, and with two different geofoam with different thicknesses. Results are presented in a comparative form and the effect of geofoam on the impact behavior of sand layer is investigated. Impact load and accelerations on the pipes are measured with respect to time during experiments. Absorbed energy by the pipes are calculated and compared with each other for determining performance of the different protective structures. From the study, it was observed that the sand and geofoam layers used as protective layers were generally successful by reducing the detrimental effects of impact loads in terms of dissipating impact effects on the pipes and the measured acceleration and displacement levels. The best result is obtained from the 50 mm thick geofoam with sand layer. Finite elements analyses are performed by using ABAQUS software and both test and analysis results are compared to obtain a model that can give an idea to designers. [ABSTRACT FROM AUTHOR]

Highlights: [•] Composite materials. [•] Strengthening techniques. [•] RC slab with opening. [•] CFRP materials. [ABSTRACT FROM AUTHOR]

Abstract: The results from an experimental blasting program that was performed at the special explosives training field of the General Directorate of Security in Ankara, where new residential blocks are planned to be constructed nearby, are presented. With the objective of estimating the blast-induced ground vibration effects on the proposed structures, various blasting parameters of nineteen surface and underground explosions were recorded in two directions at three measurement stations. Site-specific empirical relationships between peak particle velocity, the amount of explosive and the distance were developed. These relationships were used to construct a practical blasting chart, which gives the maximum amount of explosive to be used as a function of distance, for future underground and surface blasting operations in the training field. Since the use of peak particle velocity in the field of civil engineering has been limited so far, site-specific parameters were also estimated to predict the blast-induced horizontal peak ground acceleration. Then, an attempt was made to investigate the dynamic responses of four and six storey reinforced concrete structures that consist of frame and shear wall type structural systems under the measured accelerations using finite element analysis. The limitations of this approach were discussed within the context of damage estimation. [Copyright &y& Elsevier]

Abstract: The purpose of this study was to investigate the hysteretic behavior of shear deficient reinforced concrete (RC) walls that were strengthened with carbon fiber reinforced polymer (CFRP) strips. Totally, ½ scale five specimens with 1.5 aspect ratio walls were constructed. One of them was tested without any retrofitting as a reference specimen and four of them were retrofitted specimens with CFRP strips. All of the specimens were tested under cyclic lateral loading. CFRP strips with different configurations were tested like X-shaped, horizontal and parallel strips or combinations of them. All of the CFRP configurations were symmetrically bonded to both sides of the shear wall and were anchoraged to the wall. The research focuses on the effect of using CFRP strips for enhancing strength and increasing ductility of the non-seismic detailed shear walls. Test results shows that all of the CFRP strip configurations significantly improves the lateral strength, energy dissipation and deformation capacity of the shear deficient RC walls. The specimen that was strengthened with X-shaped CFRP strips was failed with premature shear failure. The specimen that was strengthened with horizontal strips was showed flexural hysteretic behavior and plastic hinge was developed at the wall base. CFRP strips were controlled shear crack propagation and resulted in improvement of displacement capacity. [Copyright &y& Elsevier]

Abstract: In many experimental studies, it is proved that URM brick walls have high strength against lateral forces acting in-plane. However, out-of-plane strength of URM brick wall against lateral forces is quite low. Therefore an experimental study is designed for improving the out-of-plane strength of URM brick walls. Specimens are manufactured by using bricks with high hollow ratios and low compressive strengths and then CFRP materials are used for strengthening. The variables examined in the study are CFRP strip layouts and usage of CFRP anchorages. The performance of strengthening technique is determined by examining strength, stiffness, ductility, energy dissipation capacity and failure modes. ACI 440 Committee report is used for calculation of the capacity of the specimens. The technique of strengthening with CFRP strips increased the strength of the specimens 9 times, ductility ratio 3.5 times; energy dissipation capacity 125 times compared to URM masonry walls. [Copyright &y& Elsevier]

Abstract: Various methods are developed for strengthening reinforced concrete beams against shear. Nowadays, external bonding of different composite members to RC beams was very popular and successful technique internationally. This study presents test results on strengthening of shear deficient RC beams by external bonding of carbon fiber reinforced polymer (CFRP) straps. Six RC beams with a T-section were tested under cyclic loading in the experimental program. Width of the CFRP straps, arrangements of straps along the shear span, and anchorage techniques that were applied at the ends of straps were the main parameters that were investigated during experimental study. Shear deficient beams with low strength concrete were strengthened by using CFRP straps for obtaining ductile flexural behavior. The test results confirmed that all CFRP arrangements improved the strength, stiffness and energy dissipation capacity of the specimens significantly. The failure mode and ductility of specimens were proved to differ according to the CFRP strap width and arrangement along the beam. Experimental results were compared with the analytical approaches that were suggested by ACI-440 Committee Report. [Copyright &y& Elsevier]

Abstract: The purpose of this study was to experimentally investigate the behavior of RC nonductile frames with RC infills under lateral loads. A total of six 1/3 scaled one bay, two story nonductile specimens were built and tested under reversed cyclic lateral load. Specimen frames were manufactured with the deficiencies commonly observed in practice. Test results showed that both the strength and the stiffness were significantly improved by the introducing infill. But the deficiency which affected the behavior of infilled frames most adversely was the presence of lap splices in column longitudinal reinforcement. In five of the test specimens’ lap splices were introduced at just the floor level and their lengths were much shorter than code requirements. Three different local strengthening techniques were applied to the infilled test specimens to overcome this deficiency. These strengthening techniques included; (a) adding continuous longitudinal reinforcements along two stories in boundary elements of infills, (b) constructing new columns on both sides of infill walls, (c) welding column lap splices. It was observed that these local strengthening techniques prevented local failure in the splice region of the frame columns and improved the lateral strength and stiffness of infilled frame considerably. [Copyright &y& Elsevier]

Abstract: The purpose of this study was to investigate experimentally the behavior of strengthened masonry infilled reinforced concrete (RC) frames using diagonal CFRP strips under cyclic loads. Ten test specimens were constructed and tested under cyclic lateral loading. Specimens were constructed as 1/3 scale, one-bay, one-storey perforated clay brick-infilled nonductile RC frames. The aspect ratio (l w/h w, where l w is the infill length and h w is the infill height) of masonry-infilled wall was 1.73. CFRP strips were applied with different widths and with three different arrangements such as on both sides (i.e. symmetrically) and on the interior side or the exterior side of the masonry walls. This experimental study investigated the effects of CFRP strips’ width and arrangement type on specimens’ behavior. Strength, stiffness and storey drifts of the test specimens were measured. Test results indicated that, CFRP strips significantly increased the lateral strength and stiffness of perforated clay brick infilled nonductile RC frames. Specimens receiving symmetrical strengthening showed higher lateral strength and stiffness. Specimens at which CFRP strips of the same width were applied to one of the interior or exterior surface of the infill wall showed similar lateral strength and stiffness. [Copyright &y& Elsevier]

Abstract: Strengthening of reinforced concrete frames by cast-in-place reinforced concrete infills is commonly used in practice. Sometimes, window or door openings have been left in the infill wall due to architectural necessities during the strengthening of RC framed buildings. But behavior of partially infilled reinforced concrete frames under lateral cyclic loads is not known fully. The purpose of this research is to investigate the behaviour of ductile reinforced concrete (RC) frames strengthened by introducing partial infills under cyclic lateral loading. One-bay, one-story, 1/3 scale nine test specimens were constructed and tested under reversed cyclic loading. Aspect ratio of the infill wall (, where length, height) and its placement configurations were the parameters of the experimental study. Test results indicated that partially infilled RC frames exhibited significantly higher ultimate strength and higher initial stiffness than the bare frame (frame with no infill). While the aspect ratio of the infill wall was increased, the lateral strength and the rigidity were increased significantly. In addition to these variables, it has been seen that the connection between frames and infills also affected the behavior of infilled frames. Specimens with partial infill walls both connected to the column and beams of the frame showed the most successful behavior. [Copyright &y& Elsevier]

Abstract: Various methods are developed for strengthening reinforced concrete beams against shear. Nowadays, external bonding of various composite members to RC beams was very popular and successfully technique internationally. This study present test results on strengthening of shear deficient RC beams by external bonding of carbon fiber reinforced polymer (CFRP) straps. Six RC beams with a T section were tested under cyclic loading in the experimental program. Width of the CFRP straps, arrangements of straps along the shear span, and anchorage technique that were applied at the ends of straps was the main parameters that were investigated during experimental study. Inclined CFRP straps were bonded along the shear spans of shear deficient beams for strengthening against shear by using epoxy. Arrangements and width of the inclined CFRP straps were the main parameters that were changed among the specimens. The test results confirmed that all CFRP arrangements improved the strength and stiffness of the specimens significantly. The failure mode, and ductility of specimens were proved to differ according to the CFRP strap width and arrangement along the beam. Experimental results were compared with the analytical approaches that were suggested by ACI-440 Committee report. [Copyright &y& Elsevier]

Abstract: Various methods are developed for strengthening reinforced concrete beams against shear. Strengthening of reinforced concrete beams using external bounding of steel plates was one of the popular research areas of recent years. This study presents test results on strengthening shear deficient reinforced concrete beams by external bonding of steel plates. Eleven reinforced concrete beams with a T-section were tested under monotonic loading in the experimental program. Three main types of steel members with different arrangements were bonded to the side of the beam webs along the shear span by using epoxy. The purpose was to obtain ductile behavior for shear deficient reinforced concrete beams. The test result confirmed that all steel plate arrangements improved the strength and stiffness of the specimens significantly. The tension reinforcement of all strengthened reinforced concrete specimens was yielded. The failure modes and ductility of specimens were proved to differ according to the type of the steel member and arrangement along the beam. Beams that were strengthened with continuous steel plate along the shear span showed ductile flexural behavior. [Copyright &y& Elsevier]

Highlights • Carbon Fibre Reinforced Polymer (CFRP) strengthened RC slabs subjected to impact load. • The arrangement and width of CFRP strips were varied. • Impact load was applied to slabs using moveable drop-weight test machine designed by the authors. • FEM of RC slabs strengthened with CFRP strips are generated using ABAQUS. Abstract There are a lot of studies focused on behaviour of reinforced concrete (RC) slabs under static and dynamic loadings in the literature. However, investigations related to Carbon Fibre Reinforced Polymer (CFRP) strengthened RC slabs subjected to impact load are still relatively rare. Consequently, an experimental study was performed in order to determine impact behaviour of two way simply supported RC slabs strengthened with CFRP strips. The arrangement and width of CFRP strips were varied in an experimental study. The impact load was applied to slabs using moveable drop-weight test machine designed by the authors. A total of nine RC slabs that were 1000 × 1000 × 80 mm dimensions were manufactured. RC slabs were strengthened using CFRP strips with a width of 50 and 100 mm as orthogonally and diagonally in both one and two directions. One of the specimens was un-strengthened and manufactured as reference specimens. The time-history of the impact force, the accelerations of two points, the center displacement of slabs and the strains of four points on CFRP strips were measured. The crack patterns of slabs are also observed. In the light of experimental results, the effects of applied strengthening method on low-velocity impact behaviour of RC slabs were determined and interpreted. Besides, the finite element models of RC slabs strengthened with CFRP strips are generated using ABAQUS software. It is found out that the proposed finite element model could be used for evaluation of dynamic responses of RC slabs strengthened with CFRP strips subjected to low-velocity impact load. [ABSTRACT FROM AUTHOR]

In this study, flexuralbehaviors of glue laminated timber beams manufactured from Pinussylvestristree were investigated by comparing the results with those of massive timber beams. The main variables considered in the study were number of laminations, types of adhesive materials and reinforcement nets used in the lamination surfaces. In scope of the experimental study, glue laminated beams with 5 and 3 lamination layers were manufactured with 90 x 90 mm beam sections. In the lamination process epoxy and polyurethane glue were used. Morever, in order to improve the bond strength at the lamination surface, aluminium, fiberglass and steel wire nets were used at the lamination surfaces. Load–displacement responses, ultimate capacities, ductility ratios, initial stiffness, energy dissipation capacities and failure mechanisms of glue laminated beams were compared with those of massive beams. It was observed that the general bending responses of glue laminated beams were better than those of massive beams. In addition to that the use of reinforcement nets at the lamination surfaces increased the ultimate load capacities of the tested beams. The highest ultimate load capacities were oberved from the tests of glue laminated beams manufactured using five laminated layers and retrofitted with polyurethane glue using steel wire reinforcement nets, in the direction normal to the lamination surface. Finally, the finite element simulations of some test specimens were performed to observe the accuracy of finite element technology in the estimation of ultimate capacities of glue laminated timber beams. [ABSTRACT FROM AUTHOR]

In recent years, there has been an increased interest in strengthening and repairing existing concrete structures, and this process requires a vast monetary investment. Therefore, today there is a need to find an appropriate and economical method to strengthen and to repair existing concrete structures. The purpose of this study is to perform experiments to understand the behavior of beams under flexure by attaching external clamps, which will behave like stirrups to improve their shear strength. This current paper reports on the study of 13 beams with differing levels of shear reinforcement deficiency. These beams were strengthened by external clamps and then experiments were performed on two groups in which the ratio of the shear span to the effective height of the beam is equal to 4.5 and 3.3 (M/Vd=a/d). Experimental results showed that this strengthening method is effective and the specimens’ strength, rigidity and ductility were improved. Clamps controlled any shear cracks and they also helped to improve ductile flexural behavior of the members. [Copyright &y& Elsevier]

• Railway track degradation in transition zones by ballast wear and breakage. • Vibration experiments with impact hammer and train passage validating a FEM. • Developed linear dynamic FEM can use investigating the effect of USP. To meet the increasing demands and be competitive in the market, railway systems must be sustainable. One of the important criteria for sustainability is to have lower life cycle costs (LCC). Several statistics report higher track geometry degradation in transition zones, and maintenance of these zones has a large share in LCC. One of the reasons behind the accelerated track degradation is the wear and the breakage of ballast in transition zones due to sudden stiffness changes and ballast vibrations. Optimized track support solutions can have a positive impact on track degradation in transition zones. Under sleeper pads (USP) as supporting elastic elements are being used to decrease stress and vibration on the ballast. In this study, numerical models with and without USP components are built for the selected transition zone. Numerical models simulate dynamic load from train passages and impact hammer load. Thus, the USP component effect on vibrational behavior of the track is analyzed. For the validation of simulations, several experiments were carried out on the selected transition zone. In addition to them, vibration mitigation experiments were performed. According to the simulation and experimental outcomes of the study, the developed models are satisfactorily in compliance with experimental results. It has been observed from simulation results that the integration of the USP component into track provides an approximately 25% decrease in ballast acceleration. On the other hand, it has a negative effect on rail and sleepers by increasing their vibration. Since this is an expected outcome of USP, the methodology in the study can be beneficial in the design phase. [ABSTRACT FROM AUTHOR]

• Strengthened low slenderness ratio RC columns with (TRM) strips are investigated. • Carbon textile is used for strengthening. • The use of CFRP fan type anchors in the strips is investigated. • Simulation models are created with the ABAQUS FEA program. An experimental and numerical study was conducted to improve the critical performance of low slenderness reinforced concrete columns, such as ultimate load capacity, initial stiffness, and energy dissipation capacity, using Textile-Reinforced Mortar (TRM) strip. A total of 17 reinforced concrete columns were fabricated and tested under uni-axial compression. The effect of carbon textile type, strip width and distance, usage of carbon fiber reinforced polymer (CFRP) fan type anchors was investigated. The experimental part of the study indicated that the ultimate load capacities of reinforced concrete columns strengthened with TRM strips was increased to 1.19–1.78 times. Their initial stiffness increased to 1.01–1.99 times, and energy dissipation capacity values increased to 1.22 and 2.09 times. In addition, simulation models for the experimental specimens were created with the ABAQUS finite element software. Then the results of analyses and the experimental outputs were compared together and interpreted. Finally, using the verified FEM model, a parametric numerical study was carried out to determine the effect of the increase in the concrete compressive strength of the column on the performance of the specimens examined within the scope of the study. According to the main findings of this study, it was demonstrated that the application of the proposed TRM strips for strengthening reinforced concrete columns was a successful method. [ABSTRACT FROM AUTHOR]

A primary failure mode for thin-walled steel members is lateral-torsional buckling (LTB), in which steel cantilever beams experience nonuniform twisting and buckling about their weak axes. Analytical and numerical studies related to the elastic LTB of cantilevers abound. However, comprehensive analytical and experimental studies focusing on the inelastic LTB behaviour of cantilevers are rare. Therefore, this study intends to establish a numerical procedure verified with experimental results to evaluate the inelastic LTB strength of steel cantilevers with an I-section. First, an experimental study was performed, in which nine steel cantilever beams with different slenderness and load-height levels were tested. Load–displacement behaviours of steel cantilevers were investigated by measuring lateral and vertical displacements and rotations under the effect of a monotonic end-point load. Subsequently, a two-step numerical procedure is introduced. The elastic LTB loads and the related mode-shapes were determined in the first step, and the nonlinear load-deflection behaviours were evaluated in the second step based on the Riks method. Finally, numerical and experimental results were compared, thereby demonstrating that the presented numerical analysis can be used for predicting the buckling loads, vertical displacements, and torsional rotations at an acceptable level in the design stage. • One of the main failure modes for a thin-walled steel member is lateral-torsional buckling. • The analytical and experimental studies focused on inelastic LTB behavior of the cantilevers are still quite rare. • The elastic LTB loads and the related mode-shapes were determined with the first step. • The nonlinear load-deflection behaviors were evaluated in the second step based on the Riks method. [ABSTRACT FROM AUTHOR]