The Investigation Of RC Beam-Column Element Under Cyclic Loading

Experimental investigation of the earthquake and post-earthquake reconnaissance suggest that the performance of reinforced concrete frame structures under earthquake loading is closely related to the behavior of beam-column joints. With the development of numerical simulation in structure engineering field, a new way which is to construct joint element model by the finite element method to simulate inelastic joint action is invented and developed. It can improve accuracy of the full-frame numerical simulation of the reinforced concrete structures with models of the under reinforced beam-column joints.The primary objective of the research effort presented here is develop an accurate and efficient joint element model. The main contents are as follows:In the first part of this paper, A series of joint models were developed to advance understanding of seismic behaviour and simulation of beam-column joints, Introducing previously proposed joint element formulations, concrete and steel model, calibration approaches and experimental data.In the second part of this paper, A joint model which based on four-node plane stress element is developed to represent the response of reinforced concrete beam-column joints under reserved cyclic loading. The element edges are divided into “joint plane” and “beam-column plane” at the joint-column interface and joint-beam interface. The inelastic mechanism of joint core is represented by the four-node plane stress element. The anchorage failures of beam and column longitudinal reinforcement embedded in the joint are determined by eight springs between “joint plane” and “beam-column plane”. The model is implemented as a four-node twenty-degree-of-freedom element. There are five degrees of freedom on each node, three of them coincide with ones of typical beam element so that the element is appropriate for use with typical hysteretic beam-column line elements in two-dimensional nonlinear analysis of reinforced concrete structure. Anumerical implementation of the new beam-column joints model was developed in ABAQUS by using user element subroutine(UEL).The third part of this paper is using fiber model based Timoshenko beam element to deals with non-linear analysis of beam and column. The element section is divided into fibers, including steel fiber and concrete fiber. Each fiber element is independent in terms of the material constitutive models, which govern the behavior. The bond slip between reinforcement bar and concrete is not considered in fiber model. The numerical results are compared with the experimental results, which demonstrate the fiber model have good accuracy to depict the cyclic behavior of concrete elements.At last, Comparison of simulated and observed response for a series of subassemblages tested in the laboratory indicates that the proposed model is appropriate for use in simulating response of building joints under cyclic loading. These subassemblages include interior joints, exterior joints and knee joints.