Post-Tensioned Glass Beams for a 9 m Spannglass Bridge

Glass beams may be reinforced to allow for a fail-safe behaviour and to avoid brittle and total collapse. This approach from reinforced concrete design is applied to glass and extended by post-tensioning the reinforcement by using Spannglass beams. A high-grade steel cable relieves the brittle material from unbeneficial tensile stress and accommodates permanent dead-load deflection. A structural concept was evolved that led to the development of Spannglass beams, which were tested for a span of 2 m. This concept was extended to larger spans in order to consider size effects and to provide this option to a broader field of application. To verify this, a 9 m pedestrian glass bridge with post-tensioned reinforcement was designed and tested experimentally. Three full-size glass specimens were utilised with adhesive connectors and two reinforcement designs. A post-tensioning concept was finalised and put into practice. Finally, four-point bending tests were performed to yield the maximum loads. This paper explains the experimental design, presents the results and provides conclusions of how to design workable structural glass beams with post-tensioned reinforcement. The paper also presents the design process and the construction of a 9 m Spannglass Bridge used by pedestrians at Glasstec 2014 in Dusseldorf, Germany.