Collapse performance of post-tensioned steel frames considering influence of infill walls

The aim of this paper is to study the effect of infill walls on load resisting behaviors of post-tensioned (PT) steel frames against collapse. Three planar PT steel frames are simulated using finite element (FE) method, one of which has no infill wall while the other two are installed with infill walls. The applied loads, lateral displacements, failure patterns, stress developments in infill walls, resisting mechanisms, as well as re-centering capabilities of three PT steel frames are studied and the role that infill walls play is discussed. Parametric analyses are conducted to investigate influences of magnitude of PT forces and critical material properties. Results indicate that infill walls work as compressive struts, significantly increasing initial stiffness, resistance and story drifts of PT steel frames, and play as energy dissipation devices during the collapse process. The existence of opening makes the stiffness distributed discontinuously throughout infill walls, greatly changing the failure pattern and increasing story drifts of PT frames. The resistances of infilled PT steel frames increase with increasing PT forces, bed joints strength and masonry unit strength in the initial stage. A design scheme is also developed to precisely predict the collapse resistance of infilled PT steel frame structures.