This paper presents a study of the role of diaphragm deformations in the seismic performance of precast parking structures. A prototype parking structure typical of structures in the Los Angeles area prior to the 1994 Northridge earthquake was studied. Nonlinear static analyses of the diaphragms and shear walls were conducted. The response of the diaphragms and shear walls in these analyses provided stiffness and strength properties for a dynamic analysis model of the structure. Significant issues related to the role of diaphragm deformations in the seismic performance of precast parking structures were identified. These include large drift demands on the gravity load system due to excessive diaphragm deformations; shear wall locations that cause the diaphragms to twist in plan, amplifying these deformations; and cross sections in critical locations in the diaphragms that have insufficient strength.
