Hybrid strengthening and flexural behaviour of post-tensioned laminated glass beams

Abstract

The strengthening of glass for structural applications is challenging. EBR (External Bonded Reinforcement) reinforcement is often preferred, although limitations result from stress concentrations especially in the case of post-tensioning. This study explores the use of CFRP (Carbon Fiber Reinforced Polymers) and/or Fe-SMA (Iron-based Shape Memory Alloys) as reinforcement in hybrid and alternative configurations. Five full size laminated glass beams were tested in flexure, combining NSM (Near-Surface Mounted) and EBR techniques and exploring the efficiency of different alternative strengthening layouts (i.e. reinforcement material versus application technique) to overcome the current shortfalls of glass strengthening for structural applications. Even for lower reinforcement ratios, hybrid strengthening systems performed better and increased load-carrying capacity while delaying crack-induced deboning failure, when compared to conventional EBR systems. Residual strength ratio increased from 87 % to 160.8 % and ductility from 407 % to 971 %. The hybrid system combining NSM-CFRP and EBR-SMA reinforcements showed the best performance, increasing the initial fracture stress of glass and maintaining sufficient residual strength capacity, while allowing the safe post-tensioning.