The paper “Effect of Dimension and Detail on the Capacity of Precast Concrete Parking Structure Diaphragms,�? published in the September-October 2003 PCI JOURNAL, presented the effect of structural dimension and construction detail on the capacity of precast concrete floor diaphragms, using parking structures as the prototype structure. Parallel research by the authors has established seismic demands for flexible diaphragm structures. In this paper, the findings of these two research steps are interpreted to propose design recommendations for precast concrete diaphragms in long floor span construction. These recommendations include provisions for diaphragm design strength, allowable flexibility, and ductility capacity based on seismic performance requirements. The provisions are incorporated into a design procedure employing performance-based design concepts. Application of the procedure is shown in a design example (Appendix B) for precast parking structure diaphragms. Research on this subject ill continue over the next several years, with funding provided by both governmental and industry organizations.
