Load‐Distribution Model for Light‐Frame Wood Roof Assemblies

Abstract

Design methods for light‐frame roof assemblies assume a weakestlink failure criterion. They provide little recognition of load‐sharing and compositeaction effects on redundant assemblies. A computer model that may be used to determine how loads are distributed in a trussed roof assembly was developed and verified on the basis of four light‐frame roof assembly tests. This model is embodied in a special‐purpose matrix frame analysis program called ROOFSYS. Simplifying assumptions made in this version of the model limit its application to the prediction of load distribution among trusses of varying stiffness, given the stiffness characteristics of individual truss elements. In addition to describing the model, behavior of light‐frame wood roof assemblies is discussed as it relates to model development and observations from the full‐scale assembly tests. If a reliable relationship between truss strength and stiffness can be established, the ROOFSYS model can be used to establish load‐sharing increase factors for light‐frame wood roof assembles.