Seismic Performance Of Connections Composed Of T-shaped CFST Columns And RC Beams With Slabs

Special-shaped concrete-filled steel tubular columns have wide range of applications because it integrates the advantage of reinforced concrete(RC)specialshaped columns with concrete-filled steel tubular(CFST),which can not only avoid the appearance of irregular edge in a room as well as improve the layout of space,but also can be applied in broad site conditions.This thesis proposes two types of connections,the end-plate and bolt connection as well as the ring-bar reinforced connection,between T-shaped CFST columns and RC beams with slabs.The experimental and numerical studies on the seismic performance of these connections are presented.The main contents and conclusions of the study are summarized as follows:(1)Seven end-plate and bolt connection between T-shaped CFST columns and RC beams with slabs specimens and six ring-bar reinforced connection specimens are tested under monotonic and cyclic loading in order to obtain the mechanical and seismic performance.The load-displacement curve and development of strains are obtained from monotonic loading test.The influence of lengths of H-shaped steel corbel,thicknesses of end-plate,diameters of high-strength bolt,number and diameter of ring-bar on seismic performance of these two types of connections are studied from cyclic loading test.The seismic behaviour of the connections in terms of hysteresis curve,skeleton curve,ductility,energy dissipation,strength degradation and stiffness degradation are evaluated.The experimental results demonstrate that these two types of connections exhibit good seismic performance.The ductility of these specimens is much better than that of RC structure and steel reinforced concrete structure.The energy dissipation ability of these specimens is better than that of reinforced concrete structure,and the strength degradation of these specimens under the cycle loading is not significant.The length of the H-shaped steel corbel,the thinkness of the end-plate,the diameter of the high-strength bolt,the diameter and number of the reinforced ringbar played important roles in improving the seismic behaviour of the connections.Moreover,all specimens failed due to damage of the concrete beam outside the corbel under the cyclic loading.These specimens achieved the desired objective of “strong column and weak beam” and “strong connection” in seismic design.(2)The finite element models for these two types of connections are formulated by a commonly finite element program ABAQUS to simulated the overall test process.The comparison between the finite element analysis and the experimental results demonstrates the accuracy of the proposed models,which can be used to predict a reliable result of the test.The influence of axial compressive force ratio of the column,reinforcement ratio of the beam,concrete strength of the beam and slab,slab and ringbar on seismic performance of these two types of connections are studied by using these models.The numerical results demonstrate that axial compressive force ratio of the column,reinforcement ratio of the beam and concrete strength of the beam and slab can affect the seismic performance of the joints in a certain range.The slab plays important role in increasing the bearing capacity and stiffness of these two types of specimens.The ring-bars are able to significantly strengthen the stiffness of the ringbar reinforced connection.(3)The simple method applied in the engineering design to calculate the moment capacity and initial stiffness of these two types of connections is proposed.The applicability of the formula was verified since the calculation proved the proposed method complies with the experimental results.