Effects of Bottom Reinforcement on Hysteretic Behavior of Posttensioned Flat Plate Connections

Abstract

Flat plate systems are commonly designed as a gravity-force-resisting system (GFRS) along with stiffer lateral-force-resisting systems (LFRS) such as shear walls, and moment resisting frames; however, deformation compatibility between the GFRS and LFRS results in positive moments (producing tension at the slab bottom) at the slab-column connections in flat plate systems. Continuous slab-bottom reinforcement (integrity reinforcement) passing through the column is required to prevent progressive collapse; however, for posttensioned flat plate (PT-flat plate) systems, there have been arguments among engineers on applying continuous slab-bottom reinforcement since ACI 318 and 352 provisions do not clearly specify the requirement on the slab-bottom reinforcement for PT flat plates. The purpose of this study is to investigate the effects of continuous slab-bottom reinforcement passing through the column core on the hysteretic behavior of the PT slab-column connections. Test results for six, 3/5 scaled specimens for interior PT flat plate connections subjected to constant gravity loads and quasistatic reversed cyclic lateral loads are presented and indicate that the slab-bottom reinforcement conforming to ACI-ASCE 352R.1 is not required to prevent collapse, but does significantly improves the hysteretic energy absorption capacity.