Application of adhesively bonded Fe-SMA for post-tensioning glass beams

Project description

Laminated glass beams and glass fins are structural elements increasingly used to support transparent roofs and facades. Constraining aspects for the design with such elements are the brittleness of the material glass and the rather low residual load-bearing capacity after initial glass failure. To obtain a ductile failure, reinforced and post-tensioned glass beams are suitable solutions. While by adding a ductile reinforcement on the tension side of a glass beam, its post-cracking behaviour and its redundancy are improved, an additional pre-stressing of this reinforcement helps to increase the initial cracking resistance as well.

An efficient pre-stressing procedure is possible with the iron-based shape memory alloy (Fe-SMA) developed by external page re-fer AG. This material can be delivered as pre-strained strips and fixed by adhesive bonding to a parent structure. After fixing the strips, a compressive stress can be induced into the parent structure by heating the Fe-SMA strip with electricity or an infrared transmitter to a certain temperature.

In a collaboration with external page re-fer AG, with support from the department for external page Structural Engineering at Empa, and funded through an external page Innosuisse innovation check (application number 51447.1 INNO-ENG), the feasibility of this novel concept was studied. Preliminary lap-shear tests, release (activation) tests and related simulations were carried out in a first step to assess the suitability and limitations of selected adhesives. In a second step, medium-scale post-tensioned glass beams with adhesively bonded Fe-SMA strips were tested in four-point bending to analyse the assembly sequence and the structural capacity.