Performance of a novel built-up column composed of four cold-formed tubes

A novel built-up column (BUC) under axial compression was experimentally investigated. The BUC consisted of four cold-formed thin-walled rectangular tubes assembled with several V-type or I-type connectors by self-tapping screws. Based on the axial loading tests of ten novel BUCs, the compressive stability of BUCs was studied, including the ultimate bearing capacity and failure mode. The relationships between load and axial shortening, lateral displacement and strain of the tubes were measured in tests. The test results were compared with predictions of codes (AISI S100-07 and GB 50018-2002) and a modified design method was developed. The results showed that the BUCs composed of four rectangular tubes assembled with V-type connectors and I-type connectors are different from classic latticed columns and battened columns in the calculation model of the transverse displacement produced by shear force. The predicted values calculated according to the suggested design method were found to be in good agreement with the experimental values of the novel BUC.