Intermediate crack-induced debonding in CFRP-retrofitted notched steel beams at different service temperatures: Experimental test and finite element modeling

Carbon fiber-reinforced polymer (CFRP)-retrofitted steel beams are likely exposed to significant service temperature variations due to seasonal and daily temperature changes. However, there is lacking research on the structural performance of CFRP-retrofitted steel beams under service temperature variations. This paper presents an experimental study of fourteen beams including one intact beam, one notched beam and twelve CFRP-retrofitted notched beams tested at various service temperatures from −20 °C to 80 °C. The structural properties including load–deflection curves, load capacities at initial and ultimate debonding, crack mouth opening displacements at the notch and the CFRP strain measurements were examined and compared at different service temperatures. The debonding loads of CFRP-retrofitted beams were increased with the temperatures from −20 °C to 60 °C and decreased at 80 °C. A formula was proposed to derive the local bond-slip behavior of the CFRP-to-steel interface at different temperatures from the CFRP strain measurements. The shear stiffness of the interface generally decreased with the service temperature growth, while the interfacial fracture energy first increased and then decreased. A finite element model was proposed to gain insight into the effects of interfacial thermal stress and temperature-dependent bond properties on the bond behavior and structural performance of CFRP-retrofitted beams at different service temperatures.