Bearing Capacity Formula of High-strength Steel CHS X-joints Under Axial Compression

Abstract:

The static performance of circular hollow section （CHS） X-joints using Q460， Q690， Q960 high-strength steel under axial compression was investigated. Using the finite element （FE） model verified by experimental results， extensive FE parametric analyses of joints were carried out. The effects of high-strength steel grades， brace-to-chord diameter ratios （β）， chord diameter-to-wall thickness ratios （2γ）， and chord axial stress ratios （n） on the structural behavior of joints were studied. Then， the suitability of the bearing capacity formula adopted by Chinese Standard GB 50017―2017 was evaluated against the results obtained from FE parametric analyses and literature test results. The conclusions can be drawn that the failure mode of joints is chord plastification， and the joint bearing capacity is often determined by the chord indentation limit， i.e.， 3% of chord diameter； the bearing capacities of high-strength steel CHS X-joints are overestimated by the formula of Chinese Standard GB 50017―2017 in most cases； the chord subjected to pressure or larger tensile forces will reduce the joint bearing capacity. Finally， the ranges of 2γ for different steel grades are recommended. Based on the plastic failure of the chord， the bearing capacity formula of CHS X-joints is proposed， considering the yield strengths of high-strength steel and the chord preload effect.