Strength of K-type HSS joint in a slim-floor truss

Abstract

In this paper, the strength of welded K-type truss joint made of high strength steel (HSS) was studied using both downscaled and full-scale dimensions. The joint consisted of two tubular bracings and a division plate that were welded to a plate chord. In scaled-down dimensions, the joints with two chord lengths made of S700MLH steel were tested and investigated by finite element (FE) analyses considering both material and geometrical non-linearity. The test results of the scaled joints showed that the joint with a shorted chord failed by a fracture in the tension bracing but with a longer chord by local buckling of the compression bracing. Good compatibility between the load-deflection curves received experimentally and numerically validated the FE models. The load-carrying capacities and displacements received from the scaled FE models were multiplied by scaling factors. The values agreed well with the strength and the displacement predicted by the full-scale models. Compared to the joint made of S355J2/S420MH steel, the joint made of S700MLH steel increased the ultimate load by 71% but decreased its ductility by 29%. The numerical and experimental results support the use of the limit strains of 2% and 5% for defining the limit load of the studied joint made of steel grades of S700MLH steel and S355J2/S420MH, respectively. The limit strains are recommended to be checked on the side face of the tension bracing at a distance of five times the steel thickness from the welds. This location is based on the congruence of the limit loads between numerical and code-based predictions.