Research On Cross-section Classification Of The Cold-formed Rectangular Hollow Section Beams Under Cyclic Loads

The cold-formed rectangular hollow section(RHS)steel structures have been widely used,because of their advantages such as convenient processing and excellent mechanical properties.Countries around the world have related contents in their codes about the cross-section classification of the cold-formed RHS under static loading,but the research on the cross-section classification of the cold-formed RHS under cyclic loading is relatively few.Meanwhile China's steel structure design specifications also don't involve the relevant contents,and China is an earthquake-prone country,it is essential to do some research on the cross-section classification of the cold-formed RHS under cyclic loading.Aimed at popularizing the use of cold-formed RHS steel structures and simplifying the design work,and based on the research results by the scholars at home and abroad,this paper analyzed the hysteretic behavior of the cold-formed RHS beams under cyclic loading through quasi-static experimental and finite element(FE)methods,then some suggestions on the cross-section classification of the cold-formed RHS under cyclic loading were given in this paper.More details of the paper are as follows:(1)Considering the strain-harding of the fillet corner,a basic 1/4 FE model of the four-point plastic bending test of the cold-formed RHS beam was built by the FE method.Then the FE analysis on the behavior of the cold-formed RHS beams was verified by comparation between the simulated data and the existing experimental data.Lastly,the specimen size and the test scheme were determined.(2)Conducting the experimental study on the cold-formed RHS beams by quasistatic experiment: Under cyclic loading,the experimental phenomena of the four specimens were recorded,and the failure modes of the cold-formed RHS beams were summarized.(3)Analysis of the experimental data: Through the experimental data,the hysteretic performances of the beams were obtained,including hysteresis curve,skeleton curve,rotation capacity,energy dissipation coefficient,stiffness degradation and deformation capacity.Meanwhile the FE model was verified by comparing the experimental results with the simulated results.(4)Parametric analysis: The stress-strain model and initial geometric imperfection of the FE model was determined through the FE analysis.Then the hysteretic behavior of the cold-formed RHS beams was simulated by the FE model.This paper summarized the influence of six parameters on the the cold-formed RHS beams,including height-tothickness ratio,width-to-thickness ratio,scale factor,thickness,steel yield strength and ratio of outer arc radius to thickness.(5)Cross-section classification suggestions: Based on the finite element analysis,the cold-formed RHS beams under cyclic loading were classified,and the limited widthto-thickness ratios of the cold-formed RHS beams were proposed.