Seismic Performance of a Novel GFRP Moment-Resisting Frame with Ductile Steel Links

Fiber-reinforced polymers (FRPs) offer many benefits, but their low ductility limits their use in primary components of moment-resisting frames (MRFs), where beam-end plastic hinging is expected. To overcome this drawback, this study introduced an innovative ductile MRF system composed of pultruded I-shaped FRP beams and columns, connected through ductile steel links that concentrate plastic deformations within the connections. This design is intended to concentrate ductility in the steel link while keeping the FRP members elastic, thereby improving energy dissipation. Using finite element modeling and parametric analyses, the influence of steel link geometry on system performance was investigated. Under the adopted modeling assumptions, the proposed hybrid system numerically exhibits stable hysteresis behavior without predicted loss of strength, stiffness, or energy dissipation, while all steel links meet AISC seismic compactness and design criteria. Although very short shear links (ρ ≤ 1) provide adequate performance, their susceptibility to damage makes short shear links (1.0 < ρ ≤ 1.6) the preferred choice. Reducing link length affects stiffness more significantly than ductility or strength. Finally, the necessary design equations for the proposed system are presented.