Shear Performance of Steel Beams with Bonded GFRP Stiffeners: Weathering and Cyclic Load Effects

Abstract

Strengthening-by-stiffening (SBS) is a technique for enhancing the shear performance of buckling-prone webs of steel beams by bonding glass fiber–reinforced polymer (GFRP) stiffeners. This paper focuses on changes in load capacity, ductility, and mode of failure of SBS under cyclic loading and after exposure to weathering conditions for 1 year. First, weathering effects on mechanical properties of the adhesive used in bonding the GFRP stiffeners are presented. The ductility of the epoxy was significantly reduced; however, the ultimate stress increased by about 68% over the ultimate stress of the nonweathered coupons. Furthermore, weathering led to the formation of a thin film of rust that propagated around the edges of the bonding adhesive for the full-scale beams. Consequently, the ultimate load capacity of the weathered beam dropped about 11% after 1 year of environmental exposure. Cyclic loading, however, resulted in negligible change in the ultimate load capacity. For all tested beams, the ductile adhesive used in bonding the GFRP stiffeners prevented a sudden drop in load capacity due to debonding of the GFRP stiffener in all tests.