New Nonlinear Roof Sheathing Fastener Model for Use in Finite-Element Wind Load Applications

Performance-based design is being developed and implemented in seismic and fire resistant design. The field of structural wind engineering has introduced several techniques that may eventually lead to performance-based wind engineering for buildings such as database assisted design. For wood-frame buildings, one deficiency is the lack of accurate load/response models with the ability to go beyond first failure leaving only force-based approaches which protect life safety but only infer certain levels of performance. This paper introduces a new nonlinear roof sheathing fastener model that is a function of not only the uplift pressure acting on the roof sheathing, but the effective moment arm (not just the moment) acting on the edge nails. A targeted set of experimental tests was conducted to determine the effect of the load eccentricity, a new stiffness matrix for a nail element formulated, and illustrative examples presented for a roof sheathing assembly analyzed using the finite element procedure. The model is shown to result in a significantly reduced capacity from current state-of-the-art finite element analyses which assume only nail withdrawal. It is anticipated that this more accurate nail model can aid in the development of performance-based wind engineering for wood-frame buildings.