Study on the Assessment of Fatigue Durability of Corroded Steel Girder Ends Repaired with Carbon Fiber Reinforced Polymer

Bridge maintenance and repair have gained significant attention as their service life continues to extend. Numerous retrofit projects have been implemented to address the corrosion issues at steel plate girders’ ends. This study focuses on evaluating the durability of the retrofitted part of the steel girder end by assessing its ability to sustain eccentric fatigue load and recognizing the possibilities of CFRP post-retrofitted damage. The novel specimen was designed to replicate corrosion on the inner side of exterior steel girder web ends and study the effect of retrofitting them with CFRP. In addition, a new bending fixture design based on the specimen design was proposed to reproduce the actual severe loading mode of a CFRP-retrofitted steel girder end. Polyurea putty (FU-Z) was used to identify the durability owing to its flexible characteristics under fatigue. The lifecycle-oriented experimental results showed that the specimens with CFRP-retrofitted steel girder ends survived for 3.5 million cycles under fatigue loading. However, specimens without polyurea putty exhibited damage characteristics, such as detachment and delamination. In addition, the shifted local stress detection of the edge joint represented the detachment of the retrofit material at 3 million cycles. The detachment occurred at the end of the corrosion web edge and delamination was observed in the cutoff section, which reduced the local bonding of 50% of the CFRP sheets. In addition, local damage resulted in durability resistance developed under elastic conditions.