Seismic Experiments And Theoretical Research Of Cfst Column-to-steel Beam Frames With Blind-bolted Endplate Connections

CFST column-to-steel beam frame with blind bolted endplate connections is composed by circle or square columns,which are combined with steel beam through enplate connection.This new style structure has many advantages,such as excellent sesmic performance,convenient connection and high bearing capacity.And it was proved by many tests that blind bolted endplate connections possess typical self-rigid characteristic.While,so far the majority of researches were confused on rigid joints structure and few scholars concerned the function of semi-rigid concrete filled steel tubular(CFST)frames.In this paper,a series of pseudo-dynamic tests and nonlinear dynamic time history analysis were conducted to CFST column-to-steel beam frames with blind bolted endplate connections for researching the seismic behavior and Dynamic response of this kind frame.Moreover,two multi-scale finite elemnt(FE)modeling were builded to discuss the affect of element type to the computation efficiency.The main contents of this thesis is depicted as follows:(1)With EI Centro seismic wave as the simulated seismic excitation input of pseudo dynamic test,two two-layer single-span CFST column-to-steel beam frames with blind bolted endplate connections were conducted by pseudo-dynamic tests.Seismic performance such as hysteretic performance,ductility dynamic magnification factor and energy dissipation were analyzed.What is more,to investigate the influence of column shape to the bearing capacity and stiffness of semi-rigid CFST frame,a square section frame and a circle section frame which have the samel section width and steel ratio were tested under equal test condition.(2)The FE model of semi-rigid CFST frames were established by using OpenSees software.The material and geometric nonlinearity was included in the models.And through adopting the simplified moment-rotation relations model and the panel zone model which is composed by 5 nodes nolinear spring element,the horizontal load(P)-horizontal displacement(?)curves under different acceleration earthquake waves were recorded and analyzed.Compared with the experimental data,the accuracy of this model was evaluated.(3)Based on the verification of FE moel in the above,few models were used to analysis the relation between different parameters and hysteretic behavior of CFST column-to-steel beam frames with blind bolted endplate connections.Meanwhile,a elastic-plastic time history analysis on the prototype structure under frequent and rear earthquake was carried out by OpenSees to research the benefit of semi-rigid joint to the sesmic behavior of overall framewaork.(4)Distinct structural multi-scale finite element analyses were presented by ABAQUS software.In simulation of frame structure,beam element was used for beam and column members,while solid elment appling was used for the column-beam joints.The concrete constitutive model of beam element applied PQ-fiber sub-programe.The results show that it is helpful for increasing operating efficiency to use multi-scale FE model after compare with solid elment model.