Novel Perspectives for Seismic Design of Hybrid Reinforced Concrete Beam Sections

Current design codes allow the use of GFRP-reinforced concrete elements only in non-seismic or low-seismicity regions, primarily due to the brittle behavior of GFRP, which limits its applicability when ductility and dissipation is required. This restriction prevents designers from fully utilizing GFRP advantageous properties in seismic zones, such as high strength, light weight, and excellent corrosion resistance. This paper proposes an innovative seismic design approach by introducing hybrid reinforced concrete beams that combine steel and GFRP reinforcement, designed and detailed to achieve adequate ductility and durability. Specifically, GFRP is positioned in the outer layer and steel reinforcement is embedded deeper within the section. This configuration enhances the durability of the section, as GFRP bars are immune to corrosion, while the use of steel increases the ductility compared to a GFRP-only reinforced section. The provided design methodology adapts current code requirements to account for the hybrid implementation of steel and GFRP reinforcement with regard to the seismic actions. The structural capacity of the hybrid section is analytically assessed and referred to the regulation performance targets considering a representative case study beam. The paper shows that the designed hybrid beam meets the regulation performance targets associated with seismic codes and is shown to be promising for implementation in seismic zones.