Investigation on ultimate capacity of built-up columns with double channel sections under axial compression

Built-up section members have been widely used in cold-formed thin-walled steel structures, but nowadays design methods for load-carrying capacity provided in related specifications in China are rather rough. The existing axial compression tests on lipped channel section members and built-up box section members, which are composed of lipped channel section members by self-drilling screws, are briefly introduced. The structural behaviors differences of built-up members and individual members were studied through existing experimental data, numerical analysis and theoretical studies. Then, the effects of installation errors and fastener spacing on built-up members' ultimate capacity were studied. Finally, a design method for built-up members with box and I sections under axial compression was proposed based on the above analysis. It can be concluded from this research that built-up box section member's global and distortional buckling strength and built-up I section member's global buckling strength are higher than corresponding single section member's strength, and the existing test results can verify the reasonability of the proposed design method. ©, 2014, Science Press. All right reserved.