EXAMINING THE APPLICABILITY OF DESIGN METHODS FOR LARGE PANELIZED ALL-WOOD ROOF DIAPHRAGMS UNDER SEISMIC LOADING

Abstract

The use of flexible roof diaphragms is very common in the United States, both for residential buildings and large-scale commercial buildings. Due to its simplicity, the traditional diaphragm design method is commonly used in diaphragm design, in particular for the design of diaphragms with relatively small dimensions. The traditional diaphragm design method assumes the axial chord forces developed in framing members under in-plane loading are carried only by the perimeter elements. The traditional diaphragm design method has always been thought to be a conservative design method, especially when applied to large diaphragms. In recent years, the engineering community began to question the applicability of the traditional diaphragm design method. A new design approach known as the collective chord design method was proposed to analyze the chord forces for very large flexible roof diaphragms. This method utilizes strain compatibility of a simple beam to estimate the axial forces in chord members. This paper evaluates the applicability of the traditional and collective chord design methods by modeling the behavior of large panelized roof diaphragms numerically.