Strength of Laminated Safety Glass

The strength of laminated safety glass continues to be treated in an overly conservative fashion by façade engineers, consultants and architects in general. The origin of this conservatism is a belief that the compliant nature of a polymer interlayer, relative to glass, results in poor transfer of shear stresses between the glass components of the laminate hence leading to greater glass stress for a given loading/support condition. In this presentation we re-examine the issue of stress development in laminated glass and present an objective protocol for designing laminates for required strength performance. The approach is based upon finite element stress analysis, with a constitutive model for the polymer interlayer, coupled with a statistical glass fracture model and a description of glass stress corrosion cracking. The approach has allowed us to develop a series of design charts for laminated glass that allows selection of interlayer thickness and glass thickness for specified loading/support scenario, temperature and loading rate. An important conclusion of our work is that four-sided simply-supported laminated glass plates under uniform pressure demonstrate comparable strength to equivalent monoliths. Indeed, in certain cases laminates may outperform equivalent monoliths. This finding is understandable since transfer of shear stresses between glass plies plays only a minor role in stress development during large deformation of plates. Our design charts and the approach are being considered by various standards bodies around the world and should lead to an objective treatment of laminated glass that will allow its true structural benefits to be realized.

Full-Text Article [119 KB]

The Authors

Dr. Anand Jagota Dr. E.I. DuPont de Nemours & Co. Anand Jagota has worked on the mechanical properties of glass and glass/polymer laminates. This work is aimed both towards the development of design standards, understanding, and improved laminated gl... Read more