Glass is generally known as a fragile material. It is sensible to the cracks created from manufacturing or contact damage. The strength of a perfect glass without crack could reach 10 GPa. By mean of strengthening such as thermal tempering, glass can be safely use for building as architectural elements and very limited to the structural elements. The authors have been developing glass strengthening methods and structural design for large scale glass beam. Some influencing factors are considered material, premature crack effect, geometry of sample and bolt. The mechanical behaviour of glass is modelled as elastic-plastic material, which show significant results in glass-bolt contact problem. The crack length, size and position provide information of a critical angle that allow to govern the crack effect in the beam connection. © Published under licence by IOP Publishing Ltd.