Mechanical Behavior Of Concrete-filled Square Steel Tubes To Steel I-section Beam Joints

Square concrete-filled tubular composite structures have obvious merits, such as high bearing capacity, good plastic and ductility, better seismic behavior, etc. So it is a composite structures which are mainly applied in underground construction, industrial workshop, multistory buildings, large span buildings, high-rise and super-tall buildings, tower and large span bridge project. The design of joints is the key that concrete-filled steel tubular structure is used in high-rise building. The study on seismic performance of joint helps to understand the mechanical behavior and improve the fabric. These works have important engineering significance and theoretic value.Based on the quasi-static experimental study of steel I-section beam to concrete-filled square steel tubes joint with side-plate welding, under low-cycle reversed loading, 3-D nonlinear finite element numerical analysis of the joint under monotonic loading and cyclic loading by using general finite element software ANSYS are established. The main work and conclusions are listed as follows:1. The theory analysis method of concrete-filled steel tubular structure is briefly summarized, and the main research status of joint in the aspect of nonlinear analysis is reviewed;2. Nonlinear analysis is conducted to analyze hysteretic behavior of steel I-section beam to concrete-filled square steel tubes joint with side-plate welding. The hysteresis loops, skeleton curves, feature loads and displacements from finite element model calculation agree well with experimental results. It is demonstrated that the nonlinear finite element models were rationally established. Meanwhile, seismic behavior indicators, such as the rigidity degradation, ductility and energy dissipation capacity compared well with the experimental results;3. In order to understand better the mechanical behavior of the joint, parametric analyses are conducted in the third section. Results show that, the expected damage occurs at the end of steel beam, close to joint area, which coincides with experimental results, and stiffener and side-plate thickness are more important to the joint; 4. Through the established simplified calculation model of joint, the procedure is implemented by numerical analysis software to calculate the load-displacement hysteresis curve of the joints. The results from the simplified calculation model correspond well with experimental results and finite element analysis results. It means that the model can be used to the preliminary design of the practical engineering and provides reference.