The strength of glass plays an important role in the dimensioning of glass components in the building industry. Here, not only parameters such as support conditions, loading rate, relative humidity etc. play an important role, but the damage by means of scratches also determines the fracture strength of glass. A heat treatment after damaging may have an influence on the resulting glass strength. The correlation between heat treatment temperature, and in particular elevated temperatures up to the glass transition temperature, and fracture stress has been studied by different researchers with several approaches of pre-treatment of specimens and test setups. This paper methodically presents various preliminary investigations which were carried out within the framework of the pre-treatment of the samples in order to investigate the influence of heat treatment of the pre-damaged samples on the fracture stress. For this purpose, double ring bending tests were performed at room temperature on pre-damaged, heat-treated soda-lime silicate glass specimens. The aim of the investigations is to obtain estimates of the extent to which a heat treatment prior to the strength test influences the fracture strength of soda-lime silicate

The surface strength of glass plays a significant role when dimensioning glass components in structural facades. Commonly soda‐lime silica glass is used as material in architectural glass design. Different environmental conditions for example the load rate, relative humidity, surface flaws etc., but also the ambient temperature can have a strong influence on the resulting surface strength. The relationship between temperature, especially elevated temperatures, and surface strength of soda‐lime silica glass has so far been rarely investigated. Therefore, this paper methodically presents an experimental test setup for the determination of bending strength at elevated temperatures as well as first results. To determine the bending tensile strength of soda‐lime silica glass as float glass, the double ring bending test was conducted on specimens with small test surfaces according to EN 1288‐5. The double ring bending tests were performed using a tensile fatigue testing machine with furnace on circular glass plates of soda‐lime silica glass in a temperature range from room temperature to 550 °C. Before testing, the specimens were first pre‐damaged (inducing crack with diamond), stored and heat treated as the final pre‐treatment step. To determine the load rate for the experiments at elevated temperatures, the experiment was simulated in advance for the various temperatures using the finite element method with consideration of structural relaxation. To account for the structural relaxation, the Narayanaswamy model was utilized.