Behavior Of Reinforced Concrete Beams Research Articles

Behavior of RC Beams with Large Openings Subjected to Pure Torsion and Retrofitted by Steel or CFRP Plates

Torsion considered with an increasingly great importance by structural engineers. Some of the typical cases are space frames, spandrel beams, beams supporting balconies, eccentrically loaded beams, spiral staircases, horizontally curved beams, skew bridges, etc. Transverse openings, in Reinforced Concrete (RC) beams may be essential required for accommodating utility services in a building structure. Provision of an opening through a beam, however, changes its simple mode of behavior to a more complex one. Therefore, the design of such beams needs special treatment. Strengthening or retrofitting of concrete structures to compensate the presence of transverse opening not only depends on the applied material but also depends on the used technique. Carbon Fiber Reinforced Polymers (CFRP) plates, provide a more technical alternative to the traditional methods of strengthening in many cases as it gives high strength, low weight, corrosion resistance, easy and quick installation and less changes in structural geometry. An experimental test program of twenty-one RC beams with central large openings subjected to pure torsion were strengthened by using additional layers of externally bonded steel or CFRP plates with different techniques. The behaviors of the tested specimens were investigated and compared to identify the effectiveness of each method and material of strengthening to increase the torsional strength of beam with different opening sizes. The main conclusions and recommendations drawn from the study were discussed and summarized. The research shows that the methods of strengthening by using externally bonded steel strips fixed by eboxy and steel dowels and CFRP plates gave best results.

Behaviour of Reinforced Concrete Beams Bonded with Glass Fibre Reinforced Polymer and Carbon Fibre Reinforced Polymer Sheets

Concrete, a mixture of different aggregates bonded with cement, first developed around 150BC in Rome has been bedrock to the modern Infrastructure. It is used to build everything from roads, bridges, dams to sky scrapers. Strengthening concrete is traditionally done by using steels but the developments in technology in recent decades allowed to use fiber reinforced plastics which are externally bonded to concrete . Such composite materials offer high strength, low weight, corrosion resistance, high fatigue resistance, easy and rapid installation and minimal change in structural geometry. This study investigates the behavior of reinforced concrete beams bonded with fiber composites. A numerical study is conducted to study the behavior of RC beam under Static third point loading. Concrete beam specimens with dimensions of 150 mm width, 300 mm height, and 2600 mm length are modelled. These beams are externally bonded with Glass Fiber Reinforced Polymer (GFRP) sheets and Carbon Fibre Reinforced Polymer (CFRP) sheets. In present study, we examine the performance of reinforced concrete beams which are bonded with GFRP and CFRP sheets with various thicknesses (1, 2 & 3 mm) using ABAQUS in terms of failure modes, enhancement of load capacity, load-deflection analysis and flexural behaviour

Flexural Behaviour of Reinforced Concrete Beam Embedded with Different Alignment of Polystyrene

Flexural Behaviour of Reinforced Concrete Beam Embedded with Different Alignment of Polystyrene

Flexural Behaviour of Reinforced Concrete Beam by using Steel Fibres & Glass Fibres

The work aims to compare the flexural behavior of concrete beam using addition of steel fibers and glass fibers with normal beam in M30 grade concrete and to find the cracks developed in the concrete beam. Experiments include Compression test, Tensile strength and Flexural strength. In this study the performance of fiber reinforced concrete(FRC) beams under two- point loading system is discussed and comparative studies were made with normal mix concrete. In this study, we are casted the cube for 7 days and beam only for 28 days. The percentage addition by mass of cement for steel fiber is 1.5 % and percentage addition by mass of coarse aggregate for glass fiber is 1%. We are going to compare the results of compression test as well as flexural strength to normal concrete through different( 1.5 and 1) percentages. Final results, the comparison of normal beam to addition of fiber reinforced concrete beam, the maximum flexural strength is found in addition of steel fiber in concrete beam.

Thermal Behaviour of Reinforced Concrete Beam with Static loading Condition.

This work examines the results on the Reinforced concrete beam element under different temperature scenario. The most contagious or maximum temperature distribution in the RC member will be presumed. In Reinforced concrete beam the flexural failure is vigorously reached by the temperature, and also steel reinforcement has experienced. The present work has studied the two-dimensional static analysis in the ABAQUS finite element software when the temperature remains in the steady-state condition during incremental loading applied in the member. The numerical results show that the temperature distribution in the beam element,load versus deflection curve ,ultimate load, Maximum principal stresses are done in the RC beam under different temperature. There fore the reinforced concrete 3D model is usefull in analytical tool for prediction of the behaviour of RC beam under temperature.

Experiment on Torsional Behaviour of Reinforced Concrete Beams

Structural beams in construction are subjected to significant torsional moment which affects the design of structures.Eight beams were produced with two distinct grade of concrete with two ratios of longitudinal as well as transverse reinforcements.An experiment for evaluation of torsional strength of reinforced concrete beams is presented in this paper.The main objective of this study is to access the role of varying percentage of transverse and longitudinal reinforcements on torsional strength of beams.Concrete grades of M 20 and M 30 beams were cast with 0.56% and 0.85% of longitudinal reinforcement as well as 50 mm and 75 mm spacing of stirrups.The experimental results are presented.The reported results include the behavioural curves and the values of torsional moment and angle of twist for entire 8 beams

Shear strengthening of RC beams using aluminum plates: An experimental work

Strengthening of the reinforced concrete (RC) beams using Aluminum plates (APs) is the most recent method. In this research, the shear strengthening of the RC beams using APs was studied experimentally. The experimental program consisted of twenty four RC beams (1/2 scale) that were tested under four-point bending flexural experiments. All beams had the same dimensions and the same internal reinforcement. Different shear strengthening techniques using APs were carried out. APs were fixed on the beam sides to enhance the shear strength vertically, inclined by 45°, diagonally and horizontally. Influence of the spacing, height and quantity of the APs was studied. The effect of the APs on the behaviour of RC beams with low compression strength of concrete was investigated. All AP techniques succeeded in enhancing the shear capacity and some of them changed the failure mode to flexural type. The highest ratio of increase of the shear strength was 76.8%. AP techniques had not increased the shear strength of the RC beams made from the weak concrete.

Long-Term Behavior of RC Beams Strengthened with Hybrid Composite Beam

This paper describes the results of long-term tests on reinforced concrete (RC) beams strengthened with hybrid composite beam (HCB) under two different sustained loads. Test specimens were fabricated to reflect the most common RC beam size used in school buildings in South Korea. The specimens had dimensions of 400 mm (width) × 600 mm (depth) × 6000 mm (length), and were tested with or without external strengthening by a hybrid composite beam (HCB). Test results showed that strengthening the RC beams with HCB not only reduced the instantaneous deflection but was also effective in decreasing long-term deflection. In this study, time-dependent factors were investigated using a modified version of the American Concrete Institute (ACI) equation. Time-dependent factors of HCB-strengthened RC beams found in the present work differed from those of other investigations due to various experimental conditions. In the present study, we found that the ACI equation may not provide a reasonable estimation of the long-term behavior of HCB-strengthened RC beams.

Моделирование разрушения армированных бетонных конструкций при ударе

Introduction : The papers presents results of an integrated experimental and numerical study on behavior of reinforced-concrete beams under impulse loading. The beams under study had three layers. The upper and lower layers were of fiber-reinforced concrete with a carbon fiber volume fraction of 0.2%. The middle layer was of concrete with metal reinforcement. Methods : Experimental studies were performed using a pile driver. A falling weight of 450 kg was dropped on a beam from a height of 0.7 m. The authors performed numerical studies based on the finite element method in a full dynamic 3D setting, using the proprietary EFES software suite considering structure fragmentation, formation of contact and free surfaces. Results : In numerical modeling, the reinforcement mesh was clearly defined. The authors studied changes over time in the stress-strain state, and fracture of reinforced-concrete beams under short-term impact loading. They developed a calculation algorithm and procedure that made it possible to analyze and predict behavior of actual structures in a full dynamic 3D setting. They also proposed a model of concrete and fiber-reinforced concrete behavior, considering anisotropy, bimodularity with regard to strength characteristics, plastic properties, and relations between strength and strain rate / pressure. Fracture dynamics in concrete beams reinforced with metal bars was studied. Good agreement of the results with the experimental data was observed.

Investigating Some Parameters Affecting Flexural Behaviour of Reinforced Concrete Beams Strengthened with CFRP Laminate

In this paper, the influence of some important parameters affecting flexural behaviour of reinforced concrete beams strengthened with one layer of CFRP laminate has been studied. For this purpose, six reinforced concrete beams were cast and tested in the laboratory. Based on the obtained data, when CFRP laminate is applied to the tension face, too close to the steel rebar, the flexural strength of the strengthened beam is reduced. In general, the performance of the beam strengthened with one wide CFRP strip is better than that strengthened with two equivalent narrow strips. Ultimate load capacity of each strengthened beam was calculated based on the method given by the ACI 440.2R and compared with the test one. It is concluded that to avoid the steel rebar-CFRP laminate interaction effect, the CFRP laminate depth to the effective depth ratio (df / d) should not be smaller than about 1.17.

Deterioration model of RC beams under marine atmospheric environment

This paper primarily proposes a deterioration model of reinforced concrete (RC) beams under marine atmospheric environment. Considering factors including corrosion initiation time, corrosion rate, corrosion non-uniformity and its effects on mechanical performances of steel bars, a comprehensive model was developed for the assessment of mechanical behaviour of RC beams under marine atmospheric environment. Also, to avoid the shortages brought by the classical truss theory, a modified compression field theory (MCFT) was applied to evaluate the effects of stirrups corrosion on the shear capacity of an RC beam. Then, according to a virtual case, the life-cycle performance of an RC beam was predicted through probability density evolution method (PDEM). Results approved the feasibility and effectiveness of the proposed model. Finally, further study work was pointed out.

Torsional strengthening of RC beams using stainless steel wire mesh -Experimental and numerical study

Locally available Stainless SteelWire Mesh (SSWM) bonded on a concrete surface with an epoxy resin is explored as an alternative method for the torsional strengthening of Reinforced Concrete (RC) beam in the present study. An experiment is conducted to understand the behavior of RC beams strengthened with a different configuration of SSWM wrapping subjected to pure torsion. The experimental investigation comprises of testing fourteen RC beams with cross section of 150 mm150 mm and length 1300 mm. The beams are reinforced with 4-10 mm diameter longitudinal bars and 2 leg-8 mm diameter stirrups at 150 mm c/c. Two beams without SSWM strengthening are used as control specimens and twelve beams are externally strengthened by six different SSWM wrapping configurations. The torsional moment and twist at first crack and at an ultimate stage as well as torque-twist behavior of SSWM strengthened specimens are compared with control specimens. Also the failure modes of the beams are observed. The rectangular beams strengthened with corner and diagonal strip wrapping configuration exhibited better enhancement in torsional capacity compared to other wrapping configurations. The numerical simulation of SSWM strengthened RC beam under pure torsion is carried out using finite element based software ABAQUS. Results of nonlinear finite element analysis are found in good agreement with experimental results.

Influence of polypropylene fibres on the shear strength of RC beams with web reinforcement

The use of various types of fibres within concrete matrix for enhancing structural performances of concrete or reinforced concrete (RC) members has been gaining interest in recent years. While a considerable amount of research has been conducted for using steel fibres, the studies on the other types of fibres are limited. For the purpose of extending our knowledge on polypropylene fibres in RC beams, an experimental programme was carried out for investigating the shear behaviour of polypropylene fibre-reinforced concrete (PFRC) beams. This paper presents the results of beams with web reinforcement divided into three groups according to the shear span-to-effective depth ratio and the amount of web reinforcement. Each group consists of a reference RC beam and three beams with fibre contents of 1.0, 2.0 and 3.0%. The simply supported beams were loaded at mid-span. Experimental results show that the addition of polypropylene fibres enhanced the shear behaviour of RC beams with web reinforcement. Furthermore, an expression for the contribution of web reinforcement was derived by considering the effectiveness of web reinforcement and it was introduced to the equation proposed previously for predicting the shear strength of PFRC beams without web reinforcement. The predictions agree with the experimental results.

Fatigue Crack Propagation Behavior of RC Beams Strengthened with CFRP under High Temperature and High Humidity Environment

Numerical and experimental methods were applied to investigate fatigue crack propagation behavior of reinforced concrete (RC) beams strengthened with a new type carbon fiber reinforced polymer (CFRP) named as carbon fiber laminate (CFL) subjected to hot-wet environment. J-integral of a central crack in the strengthened beam under three-point bending load was calculated by ABAQUS. In finite element model, simulation of CFL-concrete interface was based on the bilinear cohesive zone model under hot-wet environment and indoor atmosphere. And, then, fatigue crack propagation tests were carried out under high temperature and high humidity (50°C, 95% R · H) environment pretreatment and indoor atmosphere (23°C, 78% R · H) to obtain a-N curves and crack propagation rate, da/dN, of the strengthened beams. Paris-Erdogan formula was developed based on the numerical analysis and environmental fatigue tests.

Experimental Study on the Effect of Recycled Aggregate and GGBS on Flexural Behaviour of Reinforced Concrete Beam

Globally, the concrete industry consumes large quantities of natural resources, which are becoming insufficient to meet the increasing demands. Cement and aggregates are major constituents of concrete. Utilisation of waste materials in concrete instead of raw materials reduces environmental pollution. Ground-granulated blast-furnace slag (GGBS) is a by-product of steel industry. It has cementatious property. Recycled aggregates are obtained from demolishing waste. By using recycled concrete aggregate and GGBS in concrete we can reduce environmental problem to some extent. This experimental study evaluate the effective utilisation of GGBS and recycled aggregate in concrete. In this study GGBS is used as partial replacement for cement and recycled aggregate as partial replacement for coarse aggregate.

Behaviour of RC beams with CFRP-strengthened openings

A detailed investigation was conducted to study the behaviour of reinforced concrete (RC) beams with large openings strengthened by externally bonded carbon fibre-reinforced polymer (CFRP) laminates. A total of six simply supported beams consisting of two solid beams and four beams with openings were cast and tested under four-point bending. Each beam had a crosssection of 120 × 300 mm and length of 2000 mm. Each beam had a large opening placed symmetrically at mid-span. Test parameters included the opening shape and size as well as the strengthening configuration for the CFRP laminates. The study was conducted by way of both experimental testing and finite element analysis. The experimental results show that including a large opening at mid-span reduces the beam capacity to about 50 %. In the experimental results, strength gain due to strengthening with CFRP laminates was in the range 80–90 %. The finite element and experimental results were compared. Keywords: large opening, strengthening, CFRP, reinforced concrete beam

BEHAVIOR OF RC HOLLOW BEAM UNDER PURE CYCLIC TORSION

Twisting Moment in the member of the skeletal structure due to wind, seismic and other lateral loads are invariably repetitive and cyclic in nature. The reinforced concrete (RC) beam have been found deficient in torsional shear capacity and the behavior of RC beam under torsion is still a topic of research in structural engineering. This paper attempts to evaluate the effect of main reinforcement and shear reinforcement on the behavior of RC hollow beam under pure cyclic torsion and also studied the crack pattern. In present experimental study total 12 RC hollow beams were casted with different amount of longitudinal and shear reinforcement and tested under pure cyclic torsion. The parameters studied were cracking torque, angle of twist, energy dissipation, crack pattern and failure mode. It has been found that in pre cracking mode, reinforcement are ineffective for resisting the torsion moment but in post cracking mode all the torsional moment are resisted by the main rein-forcement. It was overserved that longitudinal reinforcement increase the torsional flexibility of beam, for the same amount of transverse reinforcement. It was also found from the experiment that optimum spacing of transverse reinforcement is equally important parameter while designing for the torsional reinforcement.

Flexural Behaviour of Reinforced Concrete Beam with Hollow Core at Various Depth

Flexural Behaviour of Reinforced Concrete Beam with Hollow Core at Various Depth

Experimental study and numerical investigation of behavior of RC beams strengthened with steel reinforced grout

The purpose of this study is to evaluate the behavior and the strength of SRG (Steel Reinforced Grout) externally strengthened Reinforced Concrete (RC) beams by using a nonlinear numerical analysis. The numerical simulation was carried out by using a three-dimensional (3D) finite element model. An interface element with a suitable damage model was used to model the connection between concrete surface and SRG reinforcing layer. The reliability of the finite element 3D-model was checked using experimental data obtained on a set of three RC beams. The parameters taken into consideration were the external configuration, with or without U-end anchorages, the concrete strength, the amount of internal tensile steel reinforcement. Conclusions were made concerning the strength and the ductility of the strengthened beams by varying the parameters and on the effectiveness of the SRG reinforcing system applied with two types of external strengthening configuration.

Evaluation of Bond Performance of RC Beams with U-Shaped Reinforcement

This study presents a simple method to improve the bond performance of reinforced concrete (RC) beams with high-strength stirrups. Experiments are carried out under cyclic loads to investigate the bond behavior of RC beams with various steel ratios and yield strengths of the transverse reinforcement. Furthermore, an analytical approach that considers the bond strength of the longitudinal reinforcement is proposed to predict the member capacity. The experimental results show that specimens with the same transverse reinforcement ratio exhibit similar bond behavior, regardless of the yield strength of the transverse reinforcing bars. The results also confirm that confining the longitudinal steel bars using the proposed U-shaped unclosed reinforcement greatly improves the bond performance of RC beams. A comparison of the analytical and experimental results shows that the proposed model predicts the test results better than the existing formulas.