The strength of annealed, heat-strengthened and fully tempered float glass

In the last two decades architectural glass has made an enormous leap from a secondary material to a material that combines structural and cladding roles. The structural role is a new and problematic one. In contrast to most other engineering materials the strength of glass is not a material parameter but a parameter dependent on processing quality and damage to the glass surface. There is also no real agreement on how strong glass is. There is a concept Euronorm for structural glass that has values for the characteristic strength for annealed, heat-strengthened, fully tempered and chemically toughened glass. There is however no real agreement on the validity of these values for design of glass beams or columns. To provide an independent set of values a statistically significant series of four-point bending tests on glass were conducted using both lying and standing positions resulting in a set of values for the characteristic strength.