Wind Design Procedures for Wood Roof Trusses of Low-Rise Structures

Abstract

Wind design procedures for wood roof trusses of low-rise structures are evaluated in this paper using wind tunnel test data and two-dimensional finite-element frame models. The adequacy of the conventional and two alternative design procedures is determined by computing the combined stress index in the top chord and the reliability index, β conditioned on the occurrence of the design wind speed. For trusses with typical design dead loads and constructed with wood that exhibits a relatively low degree of variability in material design values, the results indicate that both the conventional and the alternative design procedures considered in this study meet a target reliability index equal to 3.0. Of the three procedures, replacing main wind force resisting system (MWFRS) loads on a chord segment with components and cladding (C&C) loads, while maintaining MWFRS loads on all other chord member segments, provides the closest match to the target β. For trusses constructed with wood that exhibits a relatively high degree of variability in material design values, the reliability index is lower for all design procedures.