Cyclic behavior of substandard reinforced concrete beam-column joints with plain bars (original) (raw)
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Existing reinforced concrete (RC) buildings constructed until the mid-70's, with plain reinforcing bars, are expected to behave poorly when subjected to earthquake actions. This paper describes an experimental program designed to investigate the influence of poor detailing on the cyclic behaviour of RC beam-column joint elements. Cyclic tests were performed on five interior and five exterior full-scale beam-column joints with different detailing characteristics and reinforced with plain bars. An additional joint of each type was built with deformed bars for an evaluation of the influence of bond properties on the cyclic response of the structural element. The force-displacement global response, energy dissipation, equivalent damping and damage behaviour of the joints was investigated and the main results are presented and discussed. The experimental results indicate that the bond-slip mechanism has significantly influenced the cyclic response of the beam-column joints. The specimens built with plain bars showed lower energy dissipation, stiffness and equivalent damping.
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.
International journal of engineering research and technology, 2020
This paper is concerned with experimental study of exterior reinforced beam-column joints subject to reverse cyclic loading. Four full scale beam-column joints (had the same moment of inertia) with concrete grade 35 Mpa were tested under reversed cyclic loading, applied in quasi-static cyclic condition, to study the effect of different column shapes on the behavior of reinforced concrete beam-column Joints, The results showed that all joints exhibited the same failure mode at the interface between beam and column, rectangular column (with same width of beam) and squared column shape were higher than the regular rectangular column and circular column in the loading capacity, displacement, stiffness degradation and strength decay.
Cyclic Behavior of Composite Column-Reinforced Concrete Beam Joints
2020
In this paper, behavior of the concrete encased steel profile composite column-reinforced concrete beam connection representing interior beam-to-column joints under cyclic loading is presented. The column was designed as concrete encased I steel profile composite column according to Eurocode 4; beam was designed as regular reinforced concrete beam according to local building codes. The finite element model of the beamto-column joint was implemented in ABAQUS and numerical analysis was validated by full scale experimental study. The performance of the concrete encased steel profile composite column-reinforced concrete beam joint was compared to reinforced concrete beam-to-column joint, in order to observe the load carrying capacity and ductility. Ductility level and failure type of the joints were studied and performance of connections are compared. Comparisons were made using load-displacement relation and failure mechanism. It is found that the concrete encased steel composite colu...
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.
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.
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.
International Journal of Engineering Research and Technology (IJERT), 2020
https://www.ijert.org/effect-of-column-shape-on-the-behavior-of-reinforced-concrete-beam-column-joints-under-quasi-static-loading https://www.ijert.org/research/effect-of-column-shape-on-the-behavior-of-reinforced-concrete-beam-column-joints-under-quasi-static-loading-IJERTV9IS090478.pdf This paper is concerned with experimental study of exterior reinforced beam-column joints subject to reverse cyclic loading. Four full scale beam-column joints (had the same moment of inertia) with concrete grade 35 Mpa were tested under reversed cyclic loading, applied in quasi-static cyclic condition, to study the effect of different column shapes on the behavior of reinforced concrete beam-column Joints, The results showed that all joints exhibited the same failure mode at the interface between beam and column, rectangular column (with same width of beam) and squared column shape were higher than the regular rectangular column and circular column in the loading capacity, displacement, stiffness degradation and strength decay.
Cyclic behavior of non-seismically designed interior reinforced concrete beam-column connections
Songklanakarin Journal of Science and Technology, 2008
This paper presents a test of non-seismically detailed reinforced concrete beam-column connections under reversed cyclic load. The tested specimens represented those of the actual mid-rise reinforced concrete frame buildings, designed according to the non-seismic provisions of the ACI building code. The evaluation of 10 existing reinforced concrete frames was conducted to identify key structural and geometrical indices. It was found that there existed correlation VS structural and geometrical characteristics and the column tributary area. Hence, the column tributary area was chosen as a parameter for classifying the specimens. The test results showed that specimens representing small and medium column tributary area failed by brittle joint shear, while specimen representing large column tributary area failed by ductile flexure, even though no ductile seismic details were provided.