PITA Fiscal Year 2008 Projects - Innovative Infrastructure System
   Assessment Technology

Evaluation Of Unbonded Strand Reinforcement For Precast Concrete Floor Diaphragms

The proposed research examines the use of unbonded seven-wire steel strands for use as chord reinforcement in precast concrete floors. This construction technique will provide an improved method for providing integrity to precast concrete buildings by eliminating the need for cast-in-place concrete chord regions and brittle welded chord connections. The post-tensioned system provides a restoring force to the floor system which will limit joint openings under service and the associated leakage and corrosion associated with it. In addition the post-tensioning closes floor cracks that are generated during significant earthquake events.

The research consists of an experimental and analytical study of a precast concrete floor diaphragm. The experimental phase of the research consists of four floor diaphragm tests on a portion of a precast concrete floor. The experimental subassembly will consist of two floor panels and three floor joints. The specimens will be conducted at full scale and will represent a reduced diaphragm width. An analytical prediction of the floor response will be conducted using both simplistic design-applicable methods as well as advanced techniques using the finite element method. The results of the project will be used to assess the practicality of using post-tensioned strands as chord reinforcement for floor diaphragms.