Durability by Design: New Results on Load-Carrying Silicone Bonding

In the year 2000, the Herz-Jesu church in Munich, Germany was finalized featuring a glass façade with advanced bonded load-carrying structures. The façade was stiffened in such a way that wind- and dead-loaded glass elements were joined to stainless steel channels by a two-component silicone adhesive for load transfer. Durability aspects related to this type of bonding were already presented by the author at the previous symposium in 2003. The technical questions raised by the design of the Herz-Jesu church initiated detailed research investigations within Germany concerning the application of complex bonding geometries for structural engineering purposes. These studies comprised experimental and theoretical activities which were focused on the mechanical properties of two-component silicone adhesives as well as on the behavior of various bonding geometries resulting from the use of L- and T-type steel elements. In the context of these research activities, attention was also paid to different aspects directly or indirectly related to durability issues. Regarding adhesive material behavior, tensile, compression, and shear tests were performed on aged and unaged specimens in order to analyze the impact of an aggressive environment. Several degradation modes were induced into the specimens in a systematic manner in order to evaluate the load-bearing capacities and failure mechanisms of the different bonding geometries and in order to assess the behavior in the view of partial failure. This paper presents an overview of the obtained experimental results complemented by detailed finite element analysis results. Former results obtained for the U-type bonding geometry are reviewed in the light of new experimental findings. Furthermore, bonding geometries like the T-type bonding are assessed in a similar way as previously done for the U-type bonding geometry. Finally, the paper concludes by directly comparing all investigated bonding geometries with respect to durability aspects.