Research On Cross-section Classification Of The Cold-formed Rectagular Hollow Section Beams

In recent years, the cold-formed steel structures have been developed rapidly, because of the advantages that the cold forming process is convenient, the production process is simple, and profile can be formed is arbitrary. The cold-formed effect caused by the cold forming process makes the cold-formed steel structures’ strength is largely increased, while the plastic is reduced, compared with hot-formed steel. The performance has changed greatly. Among them, the tube structures such as RHS,and so on, are widely used because of its graceful appearance and great economic performance. In practical engineering, in order to facilitate design, people are accustomed to classify the section. At present, however, only in the steel structure design specification in 2012 to solicit the views of the draft, hot rolled steel sections are classified, but hot rolled RHS cross-section classification isn’t studied, let alone cold formed steel cross-section classification. Based on the research results of the cold-formed effect and cross-section classification of the cold-formed RHS beams by the scholars at home and abroad, this paper studied the cold-formed RHS beams’ bending properties and the effect of cold forming on RHS beams’ cross-section classification, paying attention to Chinese specification revision. This paper contains the following specific contains:Firstly, in the finite element(FE) model of the plastic bending test constructed by ANSYS, SHELL181 elements, SOLID185 elements, TARGE170 and CONTA174 contact elements were adopted, considering the effect of geometric nonlinearity, material nonlinearity, residual stress factors. In this paper, the results of the finite element simulation were compared with the experimental results, and the accuracy of the FE model was verified.Secondly, the influence of the initial imperfection amplitude and the material constitutive model on the rotational ability of the cold-formed RHS beams was studied. Combined with existing research results, the initial imperfection amplitudes, constitutive relation model and yield strength which should be used in cold-formed RHS beams in this paper to do a lot of parameter analysis were determined.Thirdly, a lot of parameter analysis was done for cold-formed RHS beams’ and hot-formed RHS beams’ cross-section classification.This paper summarized the influence of the various influence factors on the cold-formed RHS beams’ and hot rolling RHS beams’ moment-curvature curves. The section properties of thick-walled and thin-walled RHS beams were compared respectively.Finally, using the results of a large number of the finite element analysis, the effect of cold-formed effect on the cross-section classification of RHS beams with different thickness was studied, and the limited width-to-thickness ratios of the cold-formed and hot-formed RHS beams for class1 and class2 sections were proposed.