An effective diaphragm is an essential component of a structurally sound building. The diaphragm provides lateral stability for the columns and/or bearing walls, braces the compression edge of floor framing members, and distributes wind and seismic forces to elements of the vertical lateral force-resisting system.
Diaphragms are divided into two main categories: rigid and flexible. Rigid diaphragms are often idealized as infinitely rigid plates that rotate about the center of rigidity and distribute loads based on the relative stiffness of each vertical lateral force-resisting element. Concrete slabs are often analyzed as rigid diaphragms. Flexible diaphragms experience distortion under the application of lateral loads and distribute those forces based on the geometric layout of the vertical lateral forces-resisting elements. Cold-formed steel decking without a concrete topping slab is generally considered a flexible diaphragm. Whether rigid or flexible, the connection of the diaphragm to the supporting structure is critical to the performance of the system.