Sensitivity of Load Distribution in Light-Framed Wood Roof Systems due to Typical Modeling Parameters

Abstract

Because failure of roof systems in past high wind events has demonstrated the consequences of not maintaining a continuous load path from the roof to the foundation, many studies have been conducted to better understand this load path, including how loads are distributed in the system. The current study looks to add to the current knowledge of the vertical load path by focusing on uplift loads and by considering the sensitivity of different modeling parameters. This is done by developing and assessing load influence coefficient contours for various roof-to-wall (RTW) connections. An analytical model of a light-framed wood structure using finite-element software is developed. The model has a gable roof system comprised of fink trusses and is modeled in a highly detailed fashion including the explicit modeling of each connector/nail in the system. The influence coefficient plots indicate that the distribution of loads is indeed sensitive to the overall stiffness of RTW connections but is not overly sensitive to their relative stiffnesses. This was investigated by looking at cases where all connections have the same stiffness and cases where they can have different stiffnesses. However, the relative stiffness begins to have a larger impact as they begin to soften because of yielding. Furthermore, the stiffness of the sheathing connectors did not appear to have much of an impact on the distribution of load, but the sheathing stiffness itself did have a notable impact.