Seismic Performance Evaluation Of Low-yield-point Steel Plate Shear Wall

Low yield point steel as a new material has more and more applications and development in the steel shear walls, dampers and other energy dissipation structures because of its superior elongation and low yield-to-tensile ratio. In this paper, based on the steel with yield strength of 100 MPa, two different design methods are used to design six kinds of low yield point steel plate shear wall structures. A combination of finite element simulation and experiment is adopted to investigate many aspects of this structure. The main research work and relevant conclusions are as follows:(1)Three groups of low yield point steel specimens are designed and processed. The main mechanical properties were tested to obtain its stress-strain relationship, and then compared with ordinary steel. The results show that there is no significant yield platform for low yield point steel. Its elongation is 2-3 times of ordinary steel. It has a lower yield-to-tensile ratio and significant strain hardening behavior at the post yield stage.(2)One-span one-story test model of low yield point steel plate shear wall is designed by means of computational analysis and finite element numerical simulation. Horizontal low cyclic loading tests were carried out in the structural laboratory. The resisting lateral stiffness, ductility, ultimate bearing capacity, energy dissipation and deformation and stress distribution of shear wall panels are analyzed. The results show that the overall hysteresis curve of the specimen is full. It has enough capacity of ductility and energy dissipation. The structure still has a very high strength when it is loaded into a large multiple of yield displacement.(3)The compression shear machine is used to study the deformation and other characteristics of One-span one-story test model with vertical loading as exploratory research on the structural performance of low yield point steel plate shear wall.(4)Shell element of ANSYS finite element software and nonlinear layered shell element of SAP2000 are used to simulate the horizontal cyclic loading test of low yield point steel plate shear wall. The correctness of finite element model is verified by comparing the experimental results in order to provide the basis for the seismic evaluation of the low yield point steel plate shear wall system by the finite element numerical analysis.The results show that these two kinds of finite element method can better simulate the overall performance curve of specimen.(5)According to the relevant seismic requirements of China’s "code for seismic design of buildings" GB50011-2010 and "Technical specification for steel structure of tallbuildings" JGJ99-98, the low yield point steel plate shear wall model of 10-story, 15-story,20-story, 25-story was designed based on the shear bearing capacity of shear plate and the model of 10-story, 20-story was designed based on theory of " yielding before buckling".The detailed seismic design process of low yield point steel plate shear wall is presented in this paper. Compared with the stress ratio of component, horizontal seismic force and overturning moment distribution of the diffenent cases designed by two methods, the results show that the structure based on the theory of "yielding before buckling" has more advantages in the field of horizontal seismic force distribution and overturning moment distribution.(6)The seismic behavior of low yield point steel plate shear wall structure was evaluated by the method of incremental dynamic analysis(IDA). The SAP2000 finite element analysis software is used to establish the nonlinear layered shell element model and conduct the nonlinear dynamic time-history analysis for the structure under different earthquake intensity levels by many natural seismic waves and artificial seismic waves. The process of structural failure is described and the seismic performance is evaluated under the small, medium and large earthquakes in this paper. The results show that the designed structure can meet the requirements of the corresponding design specifications and achieve the standards of “the two line of defense” as a dual resisting lateral system.(7)According to the proposed value in the code for seismic design of buildings and combining with IDA analysis and single layer test, this paper presents the quantitative indexes of seismic performance for this structure: NO:1/400,IO:1/200,LF:1/100,CP:1/63. The vulnerability and anti collapse analysis of each case were carried out by using the IDA curve data. The results show that: With the increase of earthquake load, the structure begins to yield gradually and enter into the plastic state, and its good ductility performance is used to play the role of energy dissipation. The anti collapse reserve coefficient decreases with the increase of the height of structure designed by the same method. The CMR of structure which is designed by the theory of "yielding before buckling" is bigger than that of which is based on shear bearing capacity.