Design Method Research And Experimental Research On Tall Bulidings With Concrete-Filled Steel Tubular Structure

Concrete filled steel tubular structure is a type of new structure that can make the best of steel and concrete. Owing to its good behavior, the new structure is used more and more widely. However, as a complex new structure, many problems in the high-rise structural system of concrete filled steel tube have not been solved. For example, no method to judge the behavior of connections, further study on the connections to whole structure behavior, no experimental research on concrete filled steel tubular frame structure with reinforced concrete beams, no study on skeleton curve of whole structure, and so on. Based on the above-mentioned, both theoretic and experimental methods are used to solve these problems.Steel beam-column joints and reinforced concrete beam-column joints that often been used in engineering are surmised and analyzed. Innovative ring beam joints, reinforced concrete beam-enforced steel ring joints and steel beam-enforced steel ring joints were tested. Seismic behavior and rigidity of the above-mentioned joints were discussed respectively.Based on the internal force and deformation of the concrete filled steel tubular frame structure, considering two states including serviceability limit state and ultimate limit state, criterion to distinguish the rigid connection, semi-rigid connection and flexible connection is discussed.It is well known at the semi-rigid connections location not only the beam and column have the same displacement but also the joints have finite rotation stiffness, ANSYS program was used to simulate the semi-rigid connections.Such effects as internal force and displacement that the semi-rigid connections had on the concrete filled steel tubular frame structure were discussed. The formulas used to solve the beam moment under vertical load were deduced; furthermore, the formulas to determine the height ratio of standard inflection point were modified. Taking the concrete filled steel tubular frame-shear wall structure subjected to distributed load as an example, the effects of the semi-rigid connection on some coefficient were brought to light, as the displacement, moment, shear of the shear wall and shear of the frame.A free vibration equation of the semi-rigid concrete filled steel tubular frame structure is built. The formula to calculate the natural periods is derived. The effects of semi-rigid connection on natural period were studied. Assuming that concrete filled steel tubular frame-shear wall is continuous elastic structure with infinite degree of freedom, free vibration equation was built. Furthermore, the effects of semi-rigid connection on natural periods and frequencies were studied. The formula to calculate the coefficient of natural periods is deduced. ANSYS program was employed to execute the response spectrum analysis and determine the response of semi-rigid concrete filled steel tubular structure under selected earthquake excitation.A frame model with single span and two stories has been conducted and the experimental research on its seismic behavior is carried out under vertical stable loads and lateral cyclic loads.Further studies were processed on the failure modes, failure mechanism, hysteretic curve, skeleton curve, displacement ductility, stiffness degradation, energy dissipation capacity and so on.According to unified theory, hysteretic model of steel beam, reinforced concrete beam and concrete filled steel tubular structure column have been chosen respectively, then nonlinear structural analysis program called IDARC is employed to determine skeleton curve of the concrete filled steel tubular frame structure. Results obtained from program are consistent well with those obtained from experiments.