The vulnerability of residential window glass to lightweight windborne debris

This paper presents the results of an experimental investigation of the momentum threshold required to damage residential window glazing when impacted by roof shingles and wooden dowels. Shingles are among the most common sources of debris in hurricane winds, and they have been observed to be a major contributor to the breach of windows. Wooden dowels represent lightweight vegetation type windborne debris (e.g., twigs, branches). Custom launching apparatuses were constructed to achieve controllable and repeatable flight modes and speeds for the debris. More than 600 annealed residential window glass specimens were tested to quantify the momentum threshold and damage accumulation. The shingle impact experiments were conducted using varying shingle sizes, flight modes, impact angles, shingle age, impact speeds, glass specimen thicknesses, dimensions, and edge boundary conditions. The wooden dowel impact experiments include varying wooden dowel diameters and angles of impact. Vulnerability curves are provided for unprotected window glass as a function of momentum, debris type, flight mode, and angle of impact.