Development of a seismic design methodology for precast diaphragms

The Precast/Prestressed Concrete Institute (PCI) is conducting a large "area of emphasis" project, jointly funded by National Science Foundation (NSF), with an overall objective of developing a comprehensive seismic design methodology for precast concrete floor diaphragms. A multi-university research team from the University of Arizona (UA), Lehigh University (LU) and the University of California San Diego (UCSD) is performing this collaborative research. The project's research integrates nonlinear static and dynamic finite element (FE) analyses at UA with large-scale experiments and solid modeling at LU and shaking table tests and system studies at UCSD. An active industry task group oversees the planning and execution phases of the research. The integrated research approach involves: (1) Full-scale tests of isolated details under simple load combinations to determine properties for input to FE models. (2) FE models of representative floor plans analyzed under different earthquake loading conditions. (3) Earthquake simulations of structures at different levels of seismic hazard and verified by shaking table tests. (4) Realistic loading patterns applied to full-scale precast units in a multi-component load frame, corresponding to histories at critical diaphragm locations, based on seismic demands obtained in the structural analyses, and force combinations and deformation patterns obtained in the diaphragm analyses. In the research program's first year, consensus was established on: (1) the underlying design philosophy guiding the research; (2) the physical scope of the project. The full-scale detail tests, FE analyses of diaphragms and earthquake simulations are underway. The shake table test is being planned.