Modeling of asphalt roof shingle-sealant structures for prediction of local delamination under high wind loads

Abstract

An analytical model based on beam-on-elastic foundation (BOEF) principles is formulated and employed to simulate the structural response of a realistic asphalt shingle-sealant system under high wind loads. The system consists of individual three-tab shingles that are discretely bonded to the underlying shingles and subjected to differential out-of-plane pressures that are associated with high wind loads. Relevant mechanical properties for a typical modern asphalt shingle and sealant were determined experimentally and input in the proposed structural model. The model was then used to estimate the applied energy release rate, G, for the sealant strip as a function of length, location, and applied uplift pressures on the shingle. Results indicate that the G values are highly sensitive to sealant strip location and sealant length, where sealant length is defined to be along the perpendicular direction between the nail line and leading edge of the shingle, and that the sealant strip location in typical modern shingles is roughly optimized to ensure a balanced value of G at the inner and outer sealant strip edges. However, predictions also indicate that G could be further reduced by using longer sealant strips that are slightly shifted towards the leading edge of the shingle, thereby decreasing the potential for failure. Additional BOEF model simulations were performed using full-field shingle uplift displacements as input to determine the potential for estimating the average uplift pressures imparted on asphalt shingles under high wind loading conditions. Promising results were obtained regarding the suitability of the proposed BOEF-based inverse analysis technique to estimate shingle uplift pressures. In addition, G values that are scaled for high pressures associated with extreme wind conditions, and resulting in sealant separation, are in qualitative agreement with an estimate of critical energy release rate, Gc, based on the results of standard direct tensile tests reported in the literature.