This free webinar, presented by Wayne Kassian, P.Eng., Principal, Kassian Dyck & Associates, provides an overview of the behaviour and design of precast concrete floor and roof diaphragms. The general methodology applies to all types of precast concrete diaphragms, but in particular hollowcore diaphragms are discussed. In addition to discussing diaphragm design and associated connection details, the presenter highlights seismic design challenges and lessons learned from previous earthquakes. The webinar covers the following topics: • Purpose of Diaphragms • Diaphragm Behaviour – Topped and Untopped Hollowcore • Diaphragm Components – Shear Panels, Chords, Collectors and Distributors • Diaphragm Analysis • Diaphragm Design and Code Requirements • Large Openings and Force Paths • Lessons Learned From Poor Diaphragm Performance in Earthquakes