Interaction of shear and tension in welded truss connections

Abstract

In many truss joints consisting of double-angle web members welded to stems of inverted lower chord tee sections, adequate fillet weld lengths may be provided without the need for gusset plates. In such cases where a joint may also be subjected to high combinations of shear and tension, the possibility of overstressing of a tee stem exists. In the investigation of this problem, four analytical techniques, including two proposed herein, and experimental results of 30 full-scale specimen tests, 22 of which were conducted during the investigation presented herein, are presented and evaluated. Analytical and experimental results indicate that the interaction of shear and normal stresses is an important consideration in the design of such joints and that an interaction check is required.Of the many parameters investigated as part of the experimental investigation, the two that most significantly influence the magnitude of tension force that a lower chord can simultaneously carry are the magnitude of applied shear force averaged over the available web shear area and the joint configuration itself. The inclination of a diagonal web member as well as intentional joint eccentricities have little effect on the strength of these joints, although joint ductility appears to be affected by eccentricities.Although all four analytical techniques have similar overall accuracies of prediction, a method based on applying a von Mises criterion at ultimate to determine an equivalent shear area in a tee chord is recommended as being the most suitable. Based on this method, as verified and validated by comparison with extensive experimental results of tests on full-scale specimens, a simplified design curve and associated equations are developed and proposed for design office use. Key words: connection, interaction, shear, tension, welded, truss.