The observed behavior of parking structures, both during earthquakes and in subsequent research, indicates that the in-plane behavior of precast concrete double-tee (DT) diaphragms may contribute to the development of large displacements and affect the structure’s seismic performance. The objectives of this study were to develop a rigorous analytical basis for practical modeling and determination of elastic in-plane behavior of pretopped, precast concrete DT diaphragms, including deformation behavior and force distribution among connectors. The elastic in-plane behavior of ten diaphragm configurations with four types of connectors, two different connector spacings, and two different amounts of chord-member steel was analyzed and compared with that of a monolithic concrete diaphragm. The modeling concepts developed were related to overall connection behavior in the connection zone. They can also be applied to other discretely joined precast concrete structures that exhibit elastic or inelastic behavior mainly in he connection zone.
