Glass structures and plasticity: contradiction or future?

Under normal serviceability temperatures, glass behaves like a linear elastic material, which will break suddenly when tensile stresses exceed a critical value. This does not necessarily mean that fracture occurs without any visual warnings. Especially when appropriate tempered glass is used, glass beams show a considerable deformation capacity. Still, there is no plasticity involved since all deformations are linear. The main safety concept is to create an overall structural "plasticity" for the glass beam as a whole, rather than for the individual material. This is usually done by building laminates: individual glass leafs alternated with soft transparent interlayers are composed as one coherent structural element. Currently, polyvinyl butyral is the most used interlayer material. Experiments with other transparent interlay materials have been carried out at different research institutes, in order to introduce more plasticity in the structural behaviour of glass beams. Not all attempts are as successful, but some results are promising. It is the authors' opinion that the ability to create an overall structural plasticity will strongly influence the breakthrough of load bearing glass constructions. In the available literature however, the authors lack an overall picture of the current state of the art. For this reason, an attempt is made to present the actual research and different aspects of "plasticity in glass constructions" in this paper.