Throughout this paper, a new system for connecting composite sandwich wall panels is proposed. The relevant structural components are investigated with the aim of utilizing these panels as insulated wall elements in building applications or prefabricated modular systems. The adopted sandwich wall panels are composed of hand-layup glass fiber–reinforced polymer (GFRP) outer skins and low-density closed polyurethane (PU) foam core. The sandwich wall panels present an overall geometry of $\mathrm{2,880}\times 960\times 64{\mathrm{mm}}^3$ . One challenge of the proposed new system that was examined included joining the panels in the longitudinal direction (along their height) and transversally connecting (along their width) to other structural elements, similar to beams at the bottom and top. The structural performance of the sandwich wall panels was experimentally tested and thereafter analytically assessed in two cases: (1) single wall panels; and (2) two jointed wall panels. Outward localized GFRP wrinkling, followed by global buckling was observed as the dominant failure mode in both cases. Further, the capability of the proposed connection system to increase the axial load capacity of the jointed panels was evaluated. The study illustrates that axial capacity of two jointed sandwich wall panels, compared to the single sandwich wall panel, increased substantially from 91 to 152% depending on the failure modes.

The near-surface mounted (NSM) technique with carbon fibre-reinforced polymer (CFRP) composites has been proven to be one of the most effective alternatives for the flexural strengthening of existing reinforced concrete (RC) members. However, several issues remain unresolved, including the effects of elevated temperatures on the performance of these strengthened RC elements. This study experimentally investigates the mechanical performance of RC slabs strengthened with NSM-CFRP systems under elevated temperatures, using both (i) steady-state and (ii) transient heating under applied loads. The steady-state tests were conducted at 20, 40, 50, 70, and 80 °C, while the transient tests were performed at 20 and 80 °C. Deflections, strains, temperatures and loads were registered during the heating phase and during the flexural tests up to failure. These measurements were used to analyse the system response in terms of load–deflection curves, evolution of concrete and CFRP strains, and bond stresses between the epoxy adhesive and CFRP. At 80 °C, the NSM-CFRP-strengthened RC slabs exhibited an average reduction of 12.1% (steady-state) and 2.3% (transient) in ultimate strength. Moreover, the concrete crushing failure mode governed up to 70 °C, despite passing the epoxy’s glass transition temperature (54 °C), while cohesive failure of the adhesive governed the failure at 80 °C.