Structural behavior of CFRP-strengthened steel beams at different service temperatures: Experimental study and FE modeling

The structural performance of externally bonded carbon fiber-reinforced polymer (CFRP)-strengthened steel beams can be affected by different service temperatures. This study carried out three-point bending tests on thirteen beams, including two un-strengthened steel beams and eleven CFRP-strengthened steel beams, at temperatures ranging from −20 °C to 60 °C. CFRP plates with two different lengths (i.e., 300 mm and 600 mm) were used for the strengthening. The load–deflection curves, ultimate failure loads and the strain evolutions in CFRP plates were measured and compared. The results showed that the steel beams strengthened with 300 mm CFRP plates were failed due to plate-end debonding at all temperatures, and the debonding load decreased with the temperature increase. In contrast, the steel beams strengthened with 600 mm CFRP plates were failed due to CFRP rupture at −20 °C to 45 °C but plate-end debonding at 60 °C. A finite element (FE) model was proposed for predicting the experimental results, in which the temperature-dependent interfacial bond behavior was properly considered based on the results from the previous CFRP-to-steel double-lap shear tests. The FE model was extensively validated through the comparisons between the experimental and FE results of load–displacement curves and CFRP strain distributions at various load levels.