Investigation of a friction-grip connection in laminated glass

Friction-grip bolted connections are theoretically well suited for the introduction of in-plane loads in glass structures because they distribute the load over a relatively large area and thus avoid critical stress concentrations. However, the performance of friction-grip connections for laminated glass may be jeopardised over time due to viscoelastic behaviour of the interlayers and gaskets used. More specifically, the latter may lead to preload losses in the connection. However, only a few technical papers have dealt with the use of friction-grip connections in laminated glass. Experimental tests were thus performed to study the time-dependent behaviour and the slip resistance of an existing connection. The latter consisted of a polyvinyl butyral laminated glass plate bolted to steel skew plates with preloaded bolts. Different materials (e.g. styrene butadiene rubber, nylon and polyoxymetheylene(-copolymer)) were investigated for the gasket, used to avoid direct contact between glass and steel. Specimens with and without a compression ring laminated between both glass panels were compared. The investigation very clearly demonstrated the importance of gasket design as well as the negative effect of interlayer creep on the performance of the investigated friction-grip connection.