Calculating roof membrane deformation under simulated moderate wind uplift pressures

A mechanically attached roof system has flexible membranes that are exposed to environmental elements to achieve the waterproofing function. Wind induced loads can lift the roof membrane between attachment locations and cause fluttering. The membrane under tension induced by wind forces transfers stresses through fasteners at the attachment locations. By characterizing the membrane deformation with its slope and using a force-vector diagram, one can predict the critical forces on fasteners. This paper presents the use of a three-dimensional finite element (3D-FE) model for predicting membrane deformation. To validate the model, a series of benchmark experiments have been performed at the Dynamic Roofing Facility of the National Research Council of Canada. The experimental data are also used to evaluate the validity of a mechanical model. From this comparative exercise between the existing model and the newly developed one, the paper offers the designer the limitations at which the simplified mechanical model can be used.