The flat-plate floor system is generally recognized as an unsuitable structural system for resisting high-intensity lateral loads. Nevertheless, in regions of high seismicity in the U.S. this structural system is still one of the most widely used systems in multistory buildings braced by stiffer ductile frames of structural walls. Recent research has shown that even in these braced structures the conventionally-reinforced flat plate is susceptible to failures if gravity shear stresses on the floo and lateral drifts are not controlled to acceptable values. Performance of the unbonded post-tensioned flat-plate floor in a similar situation is not well known. This research studies the behavior of this structural system. The research involves design, construction, experimental testing, retrofitting, and analysis of unbonded post-tensioned flat-plate construction subjected to gravity and reversed cyclic lateral loads simulating earthquake effects. Both isolated connections and a three by three bay model floor are studied. Effects of gravity load intensity, lateral load intensity, and retrofitting techniques are the primary variables in the study. The experiments determine the suitability of this structural system to support gravity floor loads when subjected to cyclic lateral drifts typical of those occurring in buildings during intense ground shaking. One of the primary objectives is to establish guidelines for design of this structural system.
