Structural design and assessment of hybrid GFRP-steel RC beams in seismic areas

The paper addresses the challenges of designing hybrid reinforced concrete (RC) members, provided with both steel and glass fiber reinforced polymer (GFRP) bars, in seismic areas, where the limited ductility of GFRP traditionally restricts their implementation. In particular, the paper details how hybrid beams can potentially achieve ductile rotational capacities that meet seismic design code requirements despite linear elastic GFRP reinforcement behavior. Detailed technical guidance is developed for designing hybrid beams according to latest advances/codes; beams with steel, GFRP, and hybrid reinforcements were designed and evaluated for a high-seismicity Italian site, comparable to Seismic Design Category D (SDC D) in ASCE 7, also comparing capacity and demand rotational ductility. Finally, a preliminary cost analysis finds that direct material costs of the designed hybrid beam are comparable to the ones of traditional steel reinforced beams, highlighting the significantly higher sustainability of hybrid beams.