Studies On Seismic Behavior Of Vertical Composite Members

As the development of the high-rise and ultra-high-rise buildings, the conventional reinforced concrete (RC) vertical member tends to be difficult in satisfying the structural requirement, and the steel-RC composite member obtains more and more attention and has been widely used for its remarkable excellences. The steel-RC composite column and steel-RC composite wall are two examples among kinds of the new vertical composite members. Research on seismic behavior of the steel-RC composite column and the composite wall remains rather limited. In this dissertation, the deformation capacity, load-carrying capacity, and damage performance of the two forms of the vertical composite members is studied through the method of theoretical analysis, experimental research, and numerical calculation, which would provide a theory basis for the engineering application of the steel-RC composite column and the composite wall.The main work product of the dissertation is described as followings: 1) As the key component of the vertical composite member, the axial compressive mechanism of the concrete filled-steel tube column is studied, on the basis of which, the formula for calculating the centric axial compressive strength of the short concrete filled-steel tube column is proposed, and the strength enhancement factor due to steel tube confinement is introduced into the formula. 2) The confinement on the different parts of concrete caused by the steel tube and hoops is analysed, and the relationship between the axial compressive force and strain of the steel tube-RC composite column is presented. The ultimate strength state of the steel tube-RC composite column is determined through the limit analysis method, and the formula for calculating the compressive strength of the composite column is established and verified by experiment results. The ultimate compressive strain of the composite column is calculated by the method presented in this dissertation, and the deformation capacity of the composite column is compared with the RC column through an example. Based on the strength research, the upper limit value of the proportion of the steel tube confined concrete area over the overall sectional area of the composite column is suggested, meeting the requirement of which leads to the favorable compressive behavior. 3) Quasi-static tests on the steel tube-RC composite shear wall specimens subjected to high axial compressive load are conducted. The important properties of the walls are studied, i.e., the load-carrying capacity, deformation capacity, and energy dissipation. The effects of the design parameters are investigated, and the possibility of easing the requirement for axial force ratio and transverse boundary reinforcement is also explored. 4) According to the previous research about the deformation capacity of the RC members, the method for calculating the deformation capacity of the steel-RC composite column and the composite wall is developed, and numerical analysis on the sectional moment-curvature relationship of the steel/steel tube RC composite wall is conducted. 5) The energy dissipation and damage modal of the steel-RC composite column and composite wall is established based on the low-cycle cumulative damage and deterioration theory, and verified by experimental results. The damage index of the steel-RC composite column and composite wall is proposed.