Reinforced concrete beam–column joints with crossed inclined bars under cyclic deformations (original) (raw)
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Cyclic testing of reinforced concrete beam-column joints with crossed inclined bars
2007
The use of crossed inclined bars in external beam-column connections under cyclic deformations is experimentally investigated. For this purpose, test results of four Reinforced Concrete (RC) joint subassemblages subjected to constantly increasing pseudo-seismic loading are presented. The shear reinforcement in the joint area for two specimens was two pairs of inclined bars that formed a pair of X-type reinforcement. The other two specimens were conventionally reinforced joints (control specimens). The effectiveness of this X-type, non-conventional reinforcement on the overall seismic performance of the tested joints is examined. The beam and the columns of all the specimens were designed according to the requirements of ACI 318-02 and the recommendations of ACI-ASCE 352-02 (Type 2 exterior connections). The design of the joint area for one control specimen was also carried out according the ACI Design Codes and the required amount of steel stirrups (5∅8) was added in the joint body. The other control specimen had no stirrup at the joint area. Comparisons between the test results of the examined specimens indicated that the cyclic behaviour of the joints with X-bars was ameliorated with respect to the response of the control specimen without stirrups. Further, load capacity and hysteretic energy dissipation values of the joint with 2X-bars ∅14 were slightly lower than the values of the control specimen which joint area had stirrups (5∅8) according to the specifications of ACI Design Codes.
Cyclic Behavior of Exterior Reinforced Beam-Column Joint with Cross-Inclined Column Bars
IOSR Journal of Mechanical and Civil Engineering, 2014
The poor design practice of beam column joints is compounded by the high demand imposed by the adjoining flexural members (beams and columns) in the event of mobilizing their inelastic capacities to dissipate seismic energy. Unsafe design and detailing within the joint region jeopardizes the entire structure, even if other structural members conform to the design requirements. Beam moment reversals can produce high shear forces and bond breakdown into the joint resulting in cracking of the joint. The most important factors affecting the shear capacity of exterior RC beam-column joints are: the concrete compressive strength, the joint aspect ratio of the joints and number of lateral ties inside the joint. Advanced Reinforcement Pattern (ARP crossed inclined bars) is a feasible solution for increasing the shear capacity of the cyclically loaded exterior beam-column joints. The presence of inclined bars introduces an additional mechanism for shear transfer. External beamcolumn joints with crossed inclined reinforcement (ARP) modeled in Ansys Workbench showed high strength, and no appreciable deterioration even after reaching the maximum capacity. The load resisting capacity is increased as compared to that of seismic joint (IS: 13920-1993). A parametric study with cross inclined bars at the joint will be studied with different parameters like grade of concrete, tie ratio, joint aspect ratio, energy dissipation, yield ratio etc. A number of models in ANSYS 13.0 workbench and mechanical APDL are developed for different cyclic loads and boundary conditions. The joint with M50 grade of concrete is discussed in this paper.
Strength deterioration of reinforced concrete beam–column joints subjected to cyclic loading
Engineering Structures, 2009
This paper proposes a method to predict the ductile capacity of reinforced concrete beam-column joints failing in shear after the development of plastic hinges at both ends of the adjacent beams. After the plastic hinges occur at both ends of the beams, the longitudinal axial strain at the center of the beam section in the plastic hinge region is expected to increase abruptly because the neutral axis continues to move toward the extreme compressive fiber and the residual strains of the longitudinal bars continue to increase with each cycle of additional inelastic loading cycles. An increase in the axial strain of the beam section after flexural yielding contributes to a widening of the cracks in the beam-column joints, thus leading to a reduction in the shear strength of the beam-column joints. The proposed method includes the effect of longitudinal axial strain of a beam in the plastic hinge region of the beam on the joint longitudinal strain and the strength deterioration of the joint. In order to verify the shear strength and the corresponding deformability of the proposed method, test results of RC beam-column assembly were compared. Comparisons between the observed and calculated shear strengths and their corresponding deformability of the tested assemblies showed reasonable agreement.
Journal of the Civil Engineering Forum, 2021
The primary structural component supporting the other structural loads in a building is the beam-column joint. It is considered a critical area of a building which needs to be accurately designed to ensure energy is dissipated properly during the occurrence of an earthquake. Beam-column joint has the ability to offer a proper structure required to transform cyclic loads in the inelastic region but also has a direct impact on the components connected to it during the occurrence of any failure. This is one of the reasons the beam-column connection needs to be designed carefully. Therefore, this study focused on designing a beam-column joint with reinforcement according to SK SNI T-15-1991 in order to withstand cyclic loads. The test specimen used was observed to have a concrete compressive strength of 19.17 MPa while the dimension of the beam was 120 x 30 x 40 cm and the column was 30 x 30 x 200 cm, having 8Ø13.4 mm bars with 310.03 MPa yield strength (fy) as well as Ø9.8-100 mm stirr...
Structures, 2021
Cavity shear wall, as a kind of precast wall with internal cavity, is divided into strong and weak areas. It is hoped that the structure stiffness, lateral load capacity, and ductility could be better matched in the cavity shear wall. Therefore, the quasistatic tests were carried out to study the hysteretic performance of reinforced concrete cavity shear walls. Test results indicated that the regular squat shear wall's failure mode is dominated by shear and the setting of the cavity can effectively reduce the stiffness and lateral load capacity. The cavity makes the development and distribution of cracks in the sidewalls more uniform and finer, which is more conducive to energy dissipation. The rational match of the stiffness, lateral load capacity, and ductility can be achieved by arranging reasonable cavity in the shear wall. The purpose of improving the ductility and optimizing the failure mode of shear wall can also be achieved by relaxing the constraints of the bottom of the shear wall or setting several cavities. In addition, the multilayer shell model was adopted to simulate the specimens and parametric analysis was also carried out. The verification shows that the numerical model can predict the lateral responses of the cavity shear wall with reasonable accuracy. The parametric analysis shows that the initial stiffness and peak load of the shear wall would be reduced if there is cavity or horizontal seam at the bottom. However, the ductility could be improved if the cavity or horizontal seam is arranged in a reasonable combination. The influence of cavity and horizontal seam on the strain arch leads to the change of lateral capacity and response.
Behaviour of reinforced high-strength concrete beam—column joint. Part 1: experimental investigation
Structural Concrete, 2003
The beam-column joint is one of the important structural elements of reinforced concrete structures. It has been the subject of intensive research for the past four decades. To date, most of the design procedures of joints have been devoted to ordinary-strength concrete as implemented in the current international design codes. The use of high-strength concrete has become useful because of the advantages of member size limitation and higher structural capacity. However, its applicability is still limited because its behaviour, especially under combined stresses and shear, differs from ordinary-strength concrete in the presence of axial loading on the column. Consequently, the existing design guidelines are not completely applicable. In order to establish the salient features of the behaviour, namely modes of failure, deformational characteristics, strength parameters and strain development, an experimental programme was performed on beam-column joints under quasi-static monotonic loading. The influence of axial compression, along with other actions imposed on the joint including shear and bending moment, was taken into consideration. The practical aspects of using a composite structure-that is, ordinary-strength concrete of different grades at floor level and high-strength concrete along the rest of the column-were considered. The effects of different permutations of longitudinal as well as transverse reinforcement and various configurations of stirrups were also investigated.
Engineering Failure Analysis, 2020
In framed structures, both steel and reinforced concrete, beam-column joints play a very crucial role in terms of seismic resistance. Under the effects of high lateral seismic loads, beam-column joints are subjected to high forces and moments and their behaviour have a significant influence on the response of the structure. Poor seismic performance of inadequately detailed joints can lead to the total or partial collapse of reinforced concrete frame structures. The use of low strength concrete, plain reinforcing bars, problematic anchorage details and inadequate transverse reinforcement in beam-column joints are the factors increasing the failure risk of the structures during severe earthquakes. In this paper, an experimental study on the cyclic behaviour of reinforced concrete exterior beam-column joints is presented. The study aims at investigating the effects of the longitudinal beam reinforcement anchorage detail on the joint performance and quantifying the level of contribution of retrofitting the joints by fiber reinforced polymer sheets (FRP). Three different details were considered in the test program including the longitudinal reinforcement of the beam being anchored within the joint with 90-degree hooks, 180-degree hooks and straight bar (no hook). All of the test specimens were produced using low strength concrete and plain bars to represent the conditions of joints of existing deficient reinforced concrete building structures. In the first series of tests, four 2/3 scale reinforced concrete beam-column joint specimens were tested by adopting a displacement controlled and quasi-static load application method to assess the performance of joints with the above-mentioned anchorage details. The load was applied in a reversed cyclic fashion. The second series of tests were carried out on two additional specimens with the same details as described above but strengthened using FRP sheets. The response of the specimens were evaluated and compared in terms of load-drift, displacement hysteretic behaviour. It was found out that the problematic anchorage details have a very significant adverse effect on the seismic performance of the joints. On the other hand, FRP retrofitting has resulted in a significant increase in peak loads and sustained ductility particularly for the specimens for which reinforcement slippage was not a governing mode of failure.
Cyclic behavior of substandard reinforced concrete beam-column joints with plain bars
2013
An experimental investigation aimed at assessing the cyclic behavior of substandard interior beam-column joints built with plain reinforcing bars is described in this paper. Five specimens with plain reinforcing bars and one with deformed bars were tested under reversed cyclic loading. The influence of bond properties, displacement history, column axial load, and amount of reinforcement was investigated.
Title Diagonally-reinforced beam–column joints reinforced under cyclic loading
The beam–column joints in a reinforced concrete frame are vulnerable to damage caused by seismic events. The conventional detailing using transverse hoops usually results in serious joint congestion, which creates contruction problems. This paper introduces a new detail especially developed for low to medium seismicity, which involves the use of additional diagonal bars in the joint. Six half-scale interior beam–column assemblies with different joint details, namely ‘empty’, nominal transverse reinforcement and diagonal bars, tested under reversed cyclic loading are reported. The empty joint is not suitable even under moderate seismicity. The test results show that the joints containing the newly proposed detail, with or without axial compressive load present in the column, exhibit better behaviour at the lower range of ductility factors in terms of higher load-carrying capacity, greater stiffness and less strength degradation. Therefore, the newly proposed joint detail is suitable for beam–column joints of reinforced concrete buildings located in regions of low to medium seismic risk.
Study of Reinforced Concrete Beam-Column Joint
International journal of engineering research, 2015
The beam column joint is the crucial zone in a reinforced concrete moment resisting frame. It is subjected to large forces during severe ground shaking and its behaviour has a significant influence on the response of the structure. The assumption of rigid joint fails to consider the effects of high shear forces developed within the joint. The shear failure is always brittle in nature which is not an acceptable structural performance especially in seismic conditions. This paper presents a review of the postulated theories associated with the behaviour of joints. Understanding the joint behaviour is essential in exercising proper judgments in the design of joints. The paper discusses about the seismic actions on various types of joints and highlights the critical parameters that affect joint performance with special reference to bond and shear transfer.