Load-bearing Behaviour of Laminated Tempered Glass with Reground Edges

Designers use exposed glass edges to reach maximum transparency, for example within glass steps, glass beams or glass columns. These applications require mechanical finishing to achieve high optical quality and to compensate for the edge notch that results from the manufacturing process of safety glass. Regrinding of annealed glass is allowed without restrictions. In the case of glass with load bearing functions, tempered glass, heat-strengthened glass or fully tempered glass, is required. However, a risk of premature failure occurs when regrinding tempered glass because of a reduction of the compression zone at the edge. A research project at the Institute of Building Construction, Technische Universität Dresden, examined the impact of regrinding tempered glass on the load-bearing capacity of the glass edge. The study showed the load-bearing capacity decreased depending on the regrinding depth. Specifically, the study revealed a significant difference between the weakening of heat-strengthened glass and fully tempered glass due to the different inherent stress conditions of the different types of glass. Accordingly, regrinding heat-strengthened glass is possible up to a certain limit without critical weakening. To extend the previous studies, the project team conducted component tests on laminated glass beams manufactured from fully tempered glass and heat-strengthened glass with and without reground edges. The examination included tensile bending tests. The experimental results show the influence of regrinding on the load-bearing capacity of the glass components. This paper focusses on the evaluation of the component tests as well as the structural design. Moreover, the results of the pre-tests with single pane glass beams are presented and compared with the component tests. The research results will allow the utilization of structural glass elements with the highest optical quality in the future.