BEHAVIOR INSIGHTS AND PLASTIC DESIGN CONSIDERATIONS OF SSTF SYSTEMS BASED ON DETAILED FINITE ELEMENT ANALYSES OF A PROPOSED SUB-STRUCTURE

Abstract

The steel staggered truss framing (SSTF) system has been increasingly utilized due to its large column-free spaces, high construction efficiency, and favorable economic benefits. Despite its advantages, the SSTF system has yet to be incorporated in mainstream seismic design codes and is predominantly applied in low-seismic regions. The primary obstacle hindering the wider application of the SSTF system is the limited understanding of its inelastic behaviors, particularly in regard to diaphragm actions. This study firstly introduces an SSTF sub-structure that precisely reflects the diaphragm actions and the structural behaviors of SSTF systems, facilitating experimental researches and finite element (FE) analyses. Subsequently, a detailed SSTF sub-structure FE model and a pure steel truss FE model, considering the diaphragm actions and gusset plate connections, were established based on a plastically designed prototype SSTF structure in previous study. The yielding mechanism of the chord members, inelastic behaviors of the diaphragms, lateral responses, and stress distributions of the web members were investigated. Lastly, plastic design considerations involving the classification of the rigidity of the diaphragm, rotation demand of the chord member, mechanical calculation model of the truss and amplification factor of the web members were given to facilitate achieving the expected ductile failure mode of SSTF systems.