Structural glass beams with embedded GFRP, CFRP or steel reinforcement rods: comparative experimental, analytical and numerical investigations

The use of hybrid and composite solutions for structural applications represents a common approach for the development of safe design principles. Consolidated examples exist for concrete, steel and masonry structures. As a general rule, materials are combined so as to obtain an enhanced redundancy, strength and/or (lateral) stiffness for these systems. In this paper, structural laminated glass (LG) beams including reinforcement rods are investigated, and special attention is spent on the effect of embedded rod features, consisting of GFRP, CFRP or stainless steel reinforcement tendons. The examined embedded solution, as shown, can offer a certain benefit to the bending performance of traditional LG beams, including positive effects on stiffness, resistance and redundancy. The intrinsic properties of rods can otherwise largely affect the overall observations. To this aim, unpublished experimental tests are first briefly summarised for a set of 1 m span LG beams. Support for the preliminary discussion of the examined design concept is also derived from simple analytical calculations. Finite-Element (FE) numerical simulations are then presented, reporting on major expected behaviours due to variations in the geometrical/mechanical features of the rods, with respect to the experiments. A key role in the FE models is given by the reliable description of mechanical properties and interactions between the structural components. Comparative results are hence discussed for the post-fracture assessment of beam specimens. As shown, even a limited presence of reinforcing rods (≈100-to-400 the explored range for the ratio of glass-to-rods cross-sectional area) can provide ductility and redundancy to the LG beams. Maximum benefits (+30% residual resistance) are given by ductile steel rods, while positive effects can also be achieved with GFRP and CFRP tendon rods.