Seismic Performance of Steel Elements With and Without FRP Strengthening: A Review

The welded beam-to-column connections in steel moment-resisting frames (MRFs) have long been recognized as a critical structural vulnerability, particularly after the 1994 Northridge earthquake, which exposed their limited plastic rotation capacity and inability to endure large cyclic deformations. Extensive research confirmed that the inherent rigidity of welded joints prevents them from accommodating the alternating tension-compression forces generated during seismic events, leading to brittle fractures and severe loss of structural integrity. Therefore, previous studies have emphasized the necessity of incorporating energy dissipation (ED) and self-centering mechanisms to enable controlled plastic deformation and improve seismic resilience. In response, post-tensioned energy dissipating (PTED) and self-centering post-tensioned (SCPT) systems were introduced, integrating post-tensioning strands with supplemental ED components to enhance recovery capacity and reduce damage concentration. Post-tension connections with web hourglass pins, compact hollow structural steel dampers, and traditional horizontal friction systems have achieved up to 6% drift, maintaining self-centering and minimizing residual drift and permanent deformation. Additionally, fiber-reinforced polymer (FRP) composites have emerged as a widely studied retrofit solution to improve the cyclic response of steel elements. Under cyclic loading CFRP-strengthened beams showed a 35.4% improvement, while GFRP-strengthened beams exhibited a 31.5% improvement. GFRP-wrapped circular hollow steel (CHS) columns demonstrated a 73.8% increase in load capacity, highlighting the effectiveness of FRP strengthening in enhancing seismic resilience. These studies collectively highlight the growing importance of advanced ED concepts and FRP-based strengthening strategies in development of more resilient seismic resistant structural systems.