Research On Hysteretic Behavior Of CHS Members Under Complex Loading

ABSTRACT:Latticed domes have a more and more important position in the modern structural engineering as a result of the development of economy and technology,Circular hollow section members are widely used in latticed domes because of its advantages.But a sound knowledge of the collapse mechanism of steel structures under seismic load is still lacking,so that collapse of circular hollow section(CHS)members and its complicated structure under earthquake still takes place.Currently,the research of CHS members are mostly on constant axial force,but under strong earthquakes,the changing of axial force and moment in members are significant.Therefore,it is necessary to study the hysteretic behavior of CHS members under the variable axial force and cyclic lateral displacement.This paper includes the following jobs:(1)The finite element software ABAQUS is used to establish the numerical analysis model of CHS members.The correctness of the numerical analysis method is verified by simulating and comparing the experiments of the classic references.(2)Based on the previous research results,three kinds of variable axial force loading method are designed:axial force and lateral displacement have the same phase and frequency?axial force and lateral displacement have the same frequency and different phases?axial force and lateral displacement have the same phase and different frequencies.The hysteretic behavior of hot-rolled seamless CHS members under variable axial force and cyclic lateral displacement are analyzed,with members'diameter is 219mm,thickness are 4mm?6mm?10mm,slenderness ratios are 30?42,85 numerical models in all.The effects of initial axial compression ratio,axial compression ratio amplitude,phase difference,frequency difference,slenderness ratio and wall thickness on the hysteretic behavior has been investigated by comparing the hysteresis curve,skeleton curve,ductility coefficient and energy dissipation capacity of CHS members.At the same time,the CVGM micro fracture model is introduced to predict the fracture failure of some members.(3)According to the failure modes,macroscopic mechanical properties and the plastic development of the members,the failure modes of CHS members which subjected to variable axial force are divided into three categories:global instability failure,plastic local buckling,cyclic plastic failure.