Effects of Fixed Edge Conditions on the Load Resistance of Single Glass Lites

Abstract

The load resistance (LR) of glass lites is determined in the United States by use of standards based on a probabilistic model of glass breakage. These standards generally restrict design to rectangular glass lites continuously supported along one, two, three, or four sides. In addition, these standards treat single glass lites as simply supported flat rectangular plates. Historically, rigid window frames supported single glass lites holding them in place with neoprene or similar gasket material. This attachment method approximated simply supported edges that rotate about an axis parallel to the simply supported edges, deform in the plane of the glass lite, and do not deflect out-of-plane. Advances in structural silicone make it possible to produce rectangular single flat glass lites with edge fixity somewhere between that of simply supported edges and fully fixed edges. The authors applied the glass failure prediction model (GFPM) to a nonlinear finite-element model developed previously by the authors to determine the probability of breakage for selected single glass lite geometries with fully fixed edges under uniform lateral loads. The paper presents comparisons between results of analyses of lites with fixed edges with analyses of lites with simply supported edges. The comparisons indicate that not all single glass lite geometries benefit from fully fixing edges, but the benefits of doing so appear to increase as lite aspect ratio (AR) increases. The comparisons bracket benefits that can accrue from the partial fixity provided by structural silicone supports. The actual degree of fixity provided by structural silicone can only be determined experimentally, which lies outside the scope of this paper.