Experimental and numerical research on fire resistance of stainless steel tubular X-joints

Abstract

The fire test was carried out on six stainless steel square hollow section (SHS) tubular X-joints to investigate the influences of axial loading ratio in brace member, brace to chord width ratio and inclined angle between brace and chord member on the fire resistance performance of joints. The furnace temperature-time curve, surface temperature-time curve, vertical deformation-time curve, lateral deformation of chord web-time curve and failure mode for all specimens were obtained by the fire test. The test results show that, the failure modes of stainless steel SHS tubular X-joints at elevated temperatures can be divided to three types: plastic failure of chord flange, plastic failure of chord flange and web, and buckling failure of chord web. Then, the failure criterion of stainless steel SHS tubular X-joints under fire conditions was proposed: the joint can be considered to be damaged when its concave deformation of chord flange reaches 0.03 times of chord width. The finite element models of stainless steel SHS tubular X-joints were established and validated against the test data. Finally, based on the validated models, a parametric analysis was performed on the influencing factors of the fire resistance of tubular joints, and the results show that the failure temperature of stainless steel SHS tubular X-joints will be enhanced with the increase of brace to chord width ratio and chord width to thickness ratio, or with the decrease of axial loading ratio in brace member and chord preload ratio.