Diaphragm

For a floor or roof deck to function as a diaphragm, the deck must be properly connected to the framing members below it, and the collectors, chords, and drag struts that frame the diaphragm must be designed to carry the diaphragm forces into the vertical resisting elements. Concrete slabs are typically rigid diaphragms; steel deck with or without concrete fill, and wood structural panels, can be designed as either rigid or flexible depending on the relative stiffness of the vertical resisting system. Diaphragm design is a critical part of seismic and wind load analysis — a diaphragm that is not properly designed or connected can cause catastrophic failure in a major seismic event.