Feasibility of non-contacting measurement of wind-induced full-field displacements on asphalt shingles

Abstract

Understanding of deformations and the progressive failure mechanisms of asphalt shingles under wind loads is key to develop wind-resistant roofing systems, as well as standard test methods to characterize strength under representative wind loads. In fact, failure of shingles rated as resistant to winds up to 150 mph have been reported at speeds below 115 mph. Damage associated with failure of roof shingles continues to be a major source of insurance claims. Though pressure measurements can be taken at discrete points using pressure taps, no technology has been successfully deployed to measure full-field deformations on roof shingles subjected to wind loads. This paper reports on a feasibility study of three-dimensional digital image correlation (3D-DIC) as a non-contacting technique to measure full-field displacements of roof shingles under high wind loads. Feasibility is assessed based on evidence from load testing of three-tab shingles mounted on a full-scale roof panel specimen that was subjected to straight winds with speed up to 155 mph. Uplift displacements were measured on a target shingle tab. The natural color variations on the shingle exposed surface were used to provide a suitable speckle pattern for 3D-DIC measurements. It is shown that consistent 3D-DIC uplift displacement maps can be obtained up to failure. The evidence gained also highlights the importance of understanding the influence of time-dependent shingle material deformations, together with the progressive physical damage along the sealant strip.