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

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 nonlinearity. 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 loadcarrying 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.