Browsing by Subject "Concrete beams and girders"
Now showing 1 - 13 of 13
Results Per Page
Sort Options
Item Strengthening of Rc beams with prefabricated RC rectangular cross-sectional plates(Association for Scientific Research, 2011) Tekin M.; Demir A.; Turali T.; Nohutçu H.; Bagci M.The topic of this study is to strengthen cracked beams with prefabricated RC rectangular cross-sectional plates. The damaged beams were repaired by epoxy based glue. The repaired beams were strengthened using prefabricated RC rectangular crosssectional plates. The strengthening plates were bonded to the bottom face of the beams by anchorage rods and epoxy. The strengthened beams were incrementally loaded up to maximum load capacities. The experimental results were satisfactory since the load carrying capacities of damaged beams were increased approximately 47% due to strengthening. The post-elastic strength enhancement and the displacement ductility of all the beams are researched during the experiments. The experimental program was supported by a three-dimensional nonlinear finite element analysis. The experimental results were compared with the results obtained from the beam modeled with ANSYS finite element program. © Association for Scientific Research.Item Nonlinear finite element analysis of impact behavior of concrete beam(Association for Scientific Research, 2011) Kantar E.; Erdem R.T.; Anil O.The least well known loading type is the impact loading that are affecting on to RC structures. Several impact tests have been used to demonstrate the relative brittleness and impact resistance of concrete and similar construction materials. However, none of these tests has been declared to be a Standard test, at least in part due to the lack of statistical data on the variation of the results. In this study; total ten beam specimens at which five of them are manufactured from normal concrete compression strength without reinforcement are manufactured. Remaining five had high concrete compression strength. These specimens are tested under the impacts loading that are applied by dropping constant weight hammer from five different heights. The acceleration arises from the impact loading is measured against time. The change of velocity, displacement and energy is calculated for all specimens. The failure modes of the specimens with normal and high concrete compression strength are observed under the loading of constant weight impact hammer that are dropped from different heights. A finite element model that is made by using ABAQUS software is used for the simulation of experiments and model gave compatible results with experiments. © Association for Scientific Research.Item Low velocity impact behavior of concrete beam strengthened with CFRP strip(Techno Press, 2012) Kantar E.; Anil O.Nowadays CFRP (Carbon Fiber Reinforced Polymer) became widely used materials for the strengthening and retrofitting of structures. Many experimental and analytical studies are encountered at literature about strengthening beams by using this kind of materials against static loads and cyclic loads such as earthquake or wind loading for investigating their behavior. But authors did not found any study about strengthening of RC beams by using CFRP against low velocity impact and investigating their behavior. For these reasons an experimental study is conducted on totally ten strengthened RC beams. Impact loading is applied on to specimens by using an impact loading system that is designed by authors. Investigated parameters were concrete compression strength and drop height. Two different sets of specimens with different concrete compression strength tested under the impact loading that are applied by dropping constant weight hammer from five different heights. The acceleration arises from the impact loading is measured against time. The change of velocity, displacement and energy are calculated for all specimens. The failure modes of the specimens with normal and high concrete compression strength are observed under the loading of constant weight impact hammer that are dropped from different heights. Impact behaviors of beams are positively affected from the strengthening with CFRP. Measured accelerations, the number of drops up to failure and dissipated energy are increased. Finite element analysis that are made by using ABAQUS software is used for the simulation of experiments, and model gave compatible results with experiments.Item Determination of the impact behavior of concrete and reinforced concrete beams(Association for Scientific Research, 2013) Gücüyen E.; Erdem R.T.; Kantar E.; Baǧci M.Behavior types of structural members under various loads have been a main field of interest in engineering sciences. There have been several studies performed about determining the behavior of members under tensile, compression, bending and torsion loads until today. However, terrorist attacks and destructive earthquakes have aroused interests of scientists and engineers about solutions of impact problems. In this study, behavior of concrete and reinforced concrete beams under impact loads is investigated. For this purpose, a testing apparatus has been created. Data obtained from experimental study are compared with the analysis results of ABAQUS finite elements program.Item Load displacement behavior of concrete beam under monotonic static and low velocity impact load(Iran University of Science and Technology, 2014) Yilmaz M.C.; Anil Ö.; Alyavuz B.; Kantar E.Experiments were carried out to observe the influence of loading type on concrete beam specimens. Beam specimens made of similar concrete mixture with the same geometry were tested under three point static loading and low velocity drop weight impact loading. Load – displacement behavior, absorbed energy dissipation capacity, stiffnesses, failure modes of beam specimens were obtained and discussed. A finite element (FE) model was prepared in ANSYS Explicit STR software and the results of FE analysis were compared with experimental results. The loading type and loading rate havesignificant influence on the maximum load, stiffness and energy dissipation capacity. Numerical results obtained from ANSYS Explicit STR FE models are consistent with the experimental results. © 2014, Iran University of Science and Technology. All rights reserved.Item An anticipated shear design method for reinforced concrete beams strengthened with anchoraged carbon fiber-reinforced polymer by using neural network(John Wiley and Sons Ltd, 2015) Tanarslan H.M.; Kumanlioglu A.; Sakar G.Using externally bonded carbon fiber-reinforced polymer (FRP) for strengthening has been turned into a popular decision owing to its mechanical leads. Consequently, design guidelines and researchers have established several analytical equations to predict the contribution of FRP to ultimate shear capacity. The developed analytical equations projected the influence of FRP reinforcements within certain limits. However, not mentioned parameters such as the shear span-to-depth ratio and anchorage application influence the ultimate behavior of strengthened specimens. Accordingly, distant predictions between test results and code predictions are observed for the specimens in whom anchorage is applied. As an alternative method, artificial neural network (NN) can be used to predict the contribution of anchoraged carbon FRP to shear strength of de ficient reinforced concrete beams. Accordingly, two NN models with backpropagation are developed in this study. Unlike the existing design codes, the model considers the effect of anchorage and the shear span-to-depth ratio at the ultimate state. Artificial NN model is trained, validated and tested using the literature of 79 reinforced concrete beams. Then, NN results are compared with those 'theoretical' predictions calculated directly from International Federation for Structural Concrete, the American guideline (ACI 440.2R) and the Australian guideline. Within all theoretical predictions of design guidelines, fib14 provided the best predictions according to experimental results. Consequently, 25% of fib14 predictions are within ±10% of the experimental results, and also, 65% of the fib14 predictions are within ±25% of the measured values. Besides, executed comparisons indicated that the NN model is more exact than the guideline equations with respect to the experimental results and can be applied effectively within the range of parameters covered in this study. Copyright © 2014 John Wiley & Sons, Ltd.Item Experimental and numerical investigation of reinforced concrete beams with variable material properties under impact loading(Elsevier Ltd, 2016) Anil Ö.; Durucan C.; Erdem R.T.; Yorgancilar M.A.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. © 2016 Elsevier LtdItem Strengthening of reinforced concrete beams using external steel members(Techno Press, 2018) Demir A.; Ercan E.; Demir D.D.The objective of this study is to devise an alternative strengthening method to the ones available in the literature. So, external steel members were used to enhance both flexural and shear capacities of reinforced concrete (RC) beams having insufficient shear capacity. Two types of RC beams, one without stirrups and one with lacking stirrups, were prepared in the study. These beams were strengthened with external steel clamps devised by the authors and with external longitudinal reinforcements. Although the use of clamps alone didn’t have a significant effect on the load carrying capacity of the tested beams, the ductility increased approximately tenfold and the failure behavior changed from brittle to ductile. Although the use of clamps and longitudinal reinforcements together did not significantly increase the ductility of the beams, it approximately doubled their load capacities. The results of the experimental study were compared to the ones obtained from nonlinear finite element analysis (NLFEA) and it was observed that they were compatible. Finally, it can be concluded that the devised method could be applied to structural members as an alternative to methods in application due to lightness, low-cost, easy applicable and reliable. Copyright © 2018 Techno-Press, Ltd.Item Analysis of strengthened composite beams under flexural stress(Springer, 2018) Ercan E.; Arısoy B.; Demir A.; Özdemir A.A steel-concrete composite beam is composed of a steel beam and concrete slap connected with shear connectors. Composite beams are highly efficient structural members in order to load carrying capacity because the tension component of the force pair originating from bending is carried by the steel profile and the compressive component is carried by the concrete slab in composite beams. In this study, numerical and experimental analysis of steel-concrete composite and strengthened steel-concrete composite beams is presented. In experimental study, one strengthened and one un-strengthened specimens are produced and tested in bending. Strengthening is produced applying carbon fiber reinforced polymers sheet to the lower flange of the steel beam and using steel fiber reinforced concrete in the concrete slab. Specimens are tested under four-point loading test. During the tests, load, deflection and strain values are collected by data acquisition system. In numerical study, the finite element models of the steel-concrete composite beams are generated and analyzed by Atena-GiD program. Comparison and evaluations are made in terms of strength, applicability, stiffness and energy consumption about the steel-concrete composite beams with carbon fiber reinforced polymers and steel fibered concrete for both numerical and experimental results. © Springer International Publishing AG, part of Springer Nature 2018.Item Investigation of impact behavior of reinforced concrete beam to column connection strengthened with carbon fiber-reinforced polymer strips(John Wiley and Sons Inc, 2021) Kaya T.; Aras M.; Yilmaz T.; Çalişkan Ö.; Anil Ö.; Erdem R.T.Reinforced concrete (RC) members may expose to impulsive dynamic loads due to the reasons such as the explosions occurring in the interior or exterior part of them, rockfall, the vehicle crash to the bridges, the collision of masses with the effects of floods and landslide. Many studies have investigated the effects of impulsive dynamic loads on the beam, column, and slab RC structural elements have been investigated in the literature. However, the authors have not encountered any study focused on the impact behavior of beam to column connections of the frames constructing the bearing system of reinforced concrete structures. Therefore, an experimental study has been planned to investigate RC beam impact behavior to column connections strengthened with carbon fiber-reinforced polymer (CFRP) strips. The concrete compressive strength, shear reinforcement spacing, CFRP strip spacing, and input impact energy applied to test specimens were taken as experimental variables. The time histories of impact load acting on test specimens, accelerations, displacements, and the strains measured from CFRP strips have been recorded in experiments. The experimental variables' effect on dynamic responses of RC beam to column connections strengthened with CFRP strips subjected to impact load has been interpreted in detail. The study's scope and improved numerical analysis procedure have also been introduced to verify experimental results. Good agreement between numerical and experimental results demonstrated that the presented numerical procedures could be safely used for evaluation of impact behavior of RC beam to column connections strengthened with CFRP strips. © 2021 International Federation for Structural Concrete.Item Experimental investigation of impact behaviour of shear deficient RC beam to column connection(Techno-Press, 2022) Aras M.; Yılmaz T.; Çalışkan Ö.; Anıl Ö.; Erdem R.T.; Kaya T.Reinforced concrete (RC) structures may be subjected to sudden dynamic impact loads such as explosions occurring for different reasons, the collision of masses driven by rockfall, flood, landslide, and avalanche effect structural members, the crash of vehicles to the highway and seaway structures. Many analytical, numerical, and experimental studies focused on the behavior of RC structural elements such as columns, beams, and slabs under sudden dynamic impact loads. However, there is no comprehensive study on the behavior of the RC column-beam connections under the effect of sudden dynamic impact loads. For this purpose, an experimental study was performed to investigate the behavior of RC column-beam connections under the effect of low-velocity impact loads. Sixteen RC beam-column connections with a scale of 1/3 were manufactured and tested under impact load using the drop-weight test setup. The concrete compressive strength, shear reinforcement spacing in the beam, and input impact energy applied to test specimens were taken as experimental variables. The time histories of impact load acting on test specimens, accelerations, and displacements measured from the test specimens were recorded in experiments. Besides, shear and bending crack widths were measured. The effect of experimental variables on the impact behavior of RC beam-column connections has been determined and interpreted in detail. Besides, a finite element model has been established for verification and comparison of the experimental results by using ABAQUS software. It has been demonstrated that concrete strength, shear reinforcement ratio, and impact energy significantly affect the impact behavior of RC column-beam connections. Copyright © 2022 Techno-Press, Ltd.Item Investigation of impact behavior of shear deficient RC beams using nonlinear FEA(Taylor and Francis Ltd., 2024) Yılmaz T.; Erdem R.T.; Kıshı N.; Anıl Ö.In the scope of this study, the impact behavior of shear deficient RC beam was investigated by performing numerical analysis based on the finite element method and comparing it with the experimental results. The explicit dynamic analysis of 27 shear-deficient RC beams of which experiments were previously carried out by one of the authors has been conducted by utilizing ABAQUS software, and also it is aimed to establish the reasonable finite element model that is accordant with the experimental results. The variables of the experimental study were the ratio of longitudinal reinforcement on the tension side of the member, the shear-span ratio, and impact velocities. The time histories of impact load, reaction forces on supports, and the displacements measured from the mid-span of the beams were recorded during the experiments, and the energy absorption capacities of RC beams were evaluated based on an area enclosed by the impact load vs. displacement loops. It is investigated and interpreted to what extent the proposed nonlinear finite element method could be successful for analyzing the values of impact load and mid-span displacements and to what extent the explicit dynamic solution technique could be successful for simulating experiments. It is found that the maximum differences between the results obtained by numerical analysis using ABAQUS and the experimental results are 7% and 14% for impact loads and mid-span displacements, respectively. © 2022 Taylor & Francis Group, LLC.Item Experimental investigation of EBROG and bore-epoxy anchorage methods used for interior RC beam-column joints strengthened with CFRP sheets(Elsevier Ltd, 2024) Cetin K.; Altiok T.Y.; Demir A.In severe earthquakes, the energy dissipation and ductility capacities of the structures depend on the performance of the beam-column joints where the load transfer is performed. Experiences in past earthquakes have shown that damage occurs in the beam-column joints that do not have sufficient strength and rigidity. In particular, the shear failure observed in deficient detailed joints has caused the collapse of many structures. Joints are effectively retrofitted with carbon fiber reinforced polymer (CFRP) sheets to increase the earthquake safety of the structures. However, the debonding problem experienced in CFRP sheets significantly affects the efficiency of the applied retrofit and the earthquake behavior of the member. In this study, the retrofit of reinforced concrete beam-column joints with deficient shear strength was carried out with CFRP sheets by using externally bonded reinforcement on grooves (EBROG) and bore-epoxy anchorage methods. These two retrofit methods were applied to effectively utilize the full capacity of CFRP sheets by delaying the debonding. Six ½ scaled reinforced concrete (RC) interior beam–column specimens without transverse reinforcement in the joint core were constructed. One reference and five retrofitted joints were subjected to displacement-controlled cyclic loading. The shear failures in the specimens were delayed until advanced displacement levels. The use of EBROG and bore-epoxy anchorage methods improved the yield load of the specimens by 32 % to 69.05 % compared to the reference specimen. Additionally, significant increases were observed in the initial stiffness, load-carrying, and energy dissipation capacities of the retrofitted specimens up to 68 %, 64 %, and 104 %, respectively. The ductility of the retrofitted specimens increased by approximately 7 % to 26 %. The EBROG and bore-epoxy anchorage methods proved to be highly successful in preventing the early debonding of CFRP sheets. In specimens strengthened with EBROG and bore-epoxy anchorage methods, the displacement values at which the FRP sheets began to debonding approximately doubled. It was concluded that EBROG and bore-epoxy anchorage methods were more effective than the externally bonded reinforcement (EBR) method in improving the overall structural performance of the joints. © 2024 Institution of Structural Engineers