Prediction of extent of damage to metal roof panels under hail impact

Abstract

In the event of a hailstorm, several stakeholders, such as home and business owners, as well as insurance companies, are in immediate need to make a decision on repair or replacement of roofs based on their extent of damage. The body of knowledge on the structural response of roofs to hail impact is, however, limited, and as a result, the current roof design and assessment criteria suffer from the absence of a fundamental understanding of the extent of damage under region-specific hail hazards. To address this gap, the current study investigates the hail impact on metal roof panels that are commonly used in residential and commercial buildings. For this purpose, a set of finite-element (FE) impact simulations are conducted. The FE models of the hail developed for this study are first validated with the experimental test data. Hail impact simulations are then performed to assess the vulnerability of critical roof sections subjected to a range of hail diameters. For performance assessment, several measures, including visual damage, as well as displacements, strains, and stresses, are employed. The investigations are then extended to study a chain of hail impacts, which replicate the hailstorm events experienced by roofs in reality. In the first hail impact, the metal roof panels are found to undergo plastic deformations for hail diameters greater than 76.2 mm (3.0 in.). This increases the extent of damage to metal roof panels subjected to subsequent hailstones of the same size by up to 20%. The outcome of this study is expected to provide building, construction, and insurance industries with a fundamental insight necessary for condition assessment purposes. This is deemed a critical input to prevent the failure of metal roofs under hail impact.