Modulus Effect on Local Load Distribution for FRP/Steel Bonded Joint

Abstract

Rehabilitation of piping system has been a major concern in the oil and gas industries. Fibre reinforced polymers (FRPs) have been introduced as an alternative approach and increasingly used in repairing oil and gas pipeline. However, performance of pipeline repair system is decided by its load transfer ability and for FRPs, this led to the debonding issue which has been studied by many researchers. This paper describes a series of double strap shear tests under tensile load to investigate the bond performance between FRP sheets and steel plates. Adhesive failure at the steel-adhesive interface was observed to be the dominant failure mode for both glass fibre reinforced polymer (GFRP)-Steel and carbon fibre reinforced polymer (CFRP)-Steel DSJ due to its higher modulus ratio compare to FRP-adhesive interface. Strain distribution along the bond length shows that GFRP offer larger extension before debonding compared to CFRP. CFRP-Steel DSJ withstand higher ultimate load and possessed better load transfer ability compare to GFRP-Steel DSJ. The load spread throughout the CFRP-Steel DSJ bond length while only 50% of GFRP-Steel bond length were effective. The experimental result shows that the FRP type and bond area of a rehabilitated pipeline need to be taken into consideration during pipeline strengthening.