Combined half precast concrete slab and post-tensioned slab topping system for basement parking structures

Abstract

It is known that the prestressed half PC (precast) slab system has many advantages such as a reduced construction period and use of long-span one-way slab systems over reinforced concrete and half PC slab systems without prestressing. For this reason, prestressed half slabs are commonly used for both residential and basement parking structures in Korea and other countries. The prestressed half PC slab systems currently being used only have the pre-tensioning system only for PC slabs. To ensure better performance of the half PC slab system with larger span-to-depth ratio, a new system using both pre-tensioning and post-tensioning methods is suggested for basement parking structures in this paper. The main purpose of this paper was to analyse the suggested model and verify its safety and serviceability for a given span and a given load. The second purpose is to suggest a preliminary calculation process for the suggested system that satisfies the ACI 318 requirements. A parametric study is conducted in order to find the best and most economic model using four variables: (1) depth of precast concrete; (2) depth of topping concrete; (3) number of pre-tensioned tendons; and (4) number of post-tensioned tendons. The obtained model satisfies the requirements of ACI 318 in terms of working stress design.