Thinking Outside the Box: New approaches to very large flexible diaphragms

摘要

This paper discusses the past design practices of flexible diaphragms, the current trend to very large diaphragms, and the new tools available to properly evaluate and engineer these large roof systems. Higher shear demands are accommodated by higher plywood/OSB and steel deck shear capacities accepted by the IBC. A new collective chord technique is presented to more accurately reflect large diaphragm behavior. In addition, these very large diaphragms have significant lateral deflection issues that can now be evaluated in the IBC. The new AF&PA deflection equations for wood diaphragms are presented as well as a technique to compute deflections of diaphragms with collective chords or multi-zoned nailing.