Volume 1, Issue 3 (March 2004)
Durability by Design: Load Carrying Silicone Bonding, Herz Jesu Church, Munich
The design of conventional glass façades in Germany is typically based on the extensive use of point supports that keep the glass panels in position and which provide the load transfer of the façade. Besides the aesthetic disadvantage of discrete elements being visible in the glass façade, the application of point supports leads to highly concentrated stress regions substantially affecting sizing and durability of the façade components. In order to overcome these limitations, a new approach has been chosen for the design of the glass façade of the Herz Jesu Church, Munich. One peculiarity of the overall glass façade of this box-shaped building consists in horizontal and vertical glass beams used for the support of the façade. Silicone adhesives bond steel stringers along the main edges of the horizontal and vertical glass beams in order to establish load paths between beams and façade. The hereby-realized bonding design offers special features being favorable for the durability of the building. Load carrying capacities have been provided by line-type connections, substantially reducing stress concentrations. Major attention has been given to the geometric layout of the bonding. Thus, detailed finite element (FE) analysis has guided the careful selection of an adequate channel cross section for the stringers. The design philosophy of the bonding is characterized by a small exposed surface of the silicone adhesive, offering only a very small area of attack for environmental degradation. Additionally, the exposed surface is only stressed at a low level avoiding the critical combination of highly loaded areas exposed to aggressive environmental conditions. Furthermore, two principal load paths (tension and shear) are established, leading to a fail-safe design principle of the bonding. These key considerations provide major contributions to the high durability design of the glass façade bonding.