Effective Thickness Research Of Laminated Glass

Glass is used as structural materials in building construction widely, such as glass curtain wall, glass roof, glass spandrel, and so on, due to best transparency and decoration, in particular the widespread use of structural steel and reinforced concrete, which supports whole loads of building, and hence the exterior walls of buildings are no longer required for structural support. But the glass is imposed by the loads caused by the wind, snow, changes in temperature, weight of structural elements (that is the weight of the mullions, anchors, and other structural components in case of the curtain wall), and other factors. Safety or reliability must be considered while using glass as structural materials. Nowadays, laminated glasses are wildely used in building construction, such as glass curtain walls, high building windows, glass doors, bathrooms and stadiums. More reasearcher are focus on the applied technology of architecture glass.A sandwich glass is typically made up of two glass pieces with an interlayer. The interlayer can be gas materials, such as atmospheric air, inert gases (i.e. argon) (so-called insulating glass). It can be also solid materials, such as films (so-called laminated glass). Therefore, strength and crashing performance of sandwich glass is dependent on performance and thickness of the glass pieces and interlayer. The relationship between them is very useful in design of the sandwich glass, and the prediction of its service safety. However, calculation of the relationship is very complex. The mechanical performance of laminated glass was investigated in this paper.Effective thickness (ET) method brought forward by W?lfel E was developed for simplifying calculation on strength of laminated glass. It is assumed in ET method that a laminated glass can be represented by a monolithic glass in mechanical behavior. The strains in the monolithic glass and the laminated glass cased by a load are same. This monolithic glass is same as glass pieces in the laminated glass but thickness is calculated, and is called as effective thickness of the laminated glass. The monolithic glass is called as laminated glass piece.Bending strength calculated by ET calculated by reference is lower than measured values. That is to say, the ET result calculated by reference is conservative. A model calculating ET is proposed here. Bending strength calculated by ET calculated by this model is in good agreement with measured value for interlayer PVB film with thickness of 0.76 mm to 1.52 mm. It deviates from measured value by ~6% while thickness of interlayer PVB film is less than 0.38mm.In addition, research results demonstrate that bending strength increases with as PVB interlayer thickness decreased, and, however, it decreases SGP interlayer thickness increased.It was shown in stress distribution in laminated glass that two zero-stress planes exist for PVB laminated glass, and only one zero-stress plane exists for SGP laminated glass at room temperature. All the zero-stress planes are near the interlayer in PVB laminated glass, and the zero-stress planes are in the interlayer in SGP laminated glass. It is reason the bending strength for PVB glass is lower than for SGP glass.Stress distribution in laminated glass at several temperatures was investigated by finite element method of stress. Investigating results indicate that maximum main stress concentrates in a small circular area in middle part of PVB laminated glass plate for temperature of ~20℃. The circular stress central area increases toward the edge of the plate and becomes a petal shape with temperature raised. Stress in SGP laminated glass in temperature of ~20℃is a rectangular area on diagonal of the plate. As temperature rises, the rectangular stress area increases, and becomes a square area. This shows that, under different environmental temperature, the stress concentration area in laminated glass is difference and the glass broken state may be various.