ABSTRACT
Post-tensioned glass beams—Spannglass Beams—are under investigation to adapt the proven principles of reinforced concrete structures in structural glass design. An embedded steel cable in the cross section of a glass beam increases the load bearing capacity as well as the post fracture behaviour and aims for a redundant structural design as well as a material efficient utilization.
In order to reach this aim we design a combined glass beam section of two glass packages. Adhesively bonded connectors bridge the gap between the packages selectively, redirect the unbonded post-tensioned cables as needed and increase the lateral stiffness of the slender structure. Using this novel design concept, we refine the introduction of loads into the glass edge. Furthermore, we minimize the necessary material, focus on material where needed structurally and use material properties where fitted best in order to optimize the whole structure. This leads to a modular concept, which is open for individual customization as facade mullions, roof girders, glass staircases or bridges.
During follow-up research at the Technische Universität Dresden the behaviour of eight two meter long Spannglass Beams with two different cable layouts were investigated during an experimental series. We used heat-strengthened laminated safety glass with a PVB-interlayer and a section height of 150 mm. L-shaped stainless steel connectors achieved a connection. An acrylic fast curing adhesive ensured a reliable load transfer during four-point bending tests.
The results of the experimental bending tests in terms of load-strain and load-deformation correlations during alternating post-tension loads are shown and analysed. A comparison between different structural solutions will give a most suitable construction. Finally, we show the prospective performance by comparing the ultimate bending load of post-tensioned glass beams with adhesively bonded connectors and reference specimens as well as alternative options with blocked connectors from previous research.
After failure, we investigate on the breakage pattern and the remaining cable load to estimate the safety of the structure. The results show that a pointwise load transfer via adhesively bonded connector is feasible without an increased risk of failure. This way we show that this structural option may be a basis for future glass beam design.
