Experimental study on the effect of initial crack damage on the capacity degradation of RC eccentric columns

This study investigates the degradation of bearing capacity in cantilever-casting arch bridges due to construction-induced cracking. An equivalent conversion method is proposed to model the arch ring segment as an eccentric compression column. Reinforced concrete (RC) columns with constant cross-sections are designed to simulate eccentric column specimens, with crack width serving as the damage quantification index. Various initial crack widths (0 mm, 0.05 mm, 0.10 mm, and 0.15 mm) are introduced through different loading methods, and load-bearing capacity tests are performed for various damage states. The results show that initial cracks on the tensile side significantly reduce the load-bearing capacity of the eccentric columns, with the largest reductions being 18.91% and 8.33% for large and small eccentric columns, respectively. A negative correlation is observed between crack width and bearing capacity, while cracks on the compressive side have a minimal effect on the load-bearing capacity. Cracks in large eccentric columns result in reduced elastic stiffness, early yielding of reinforcement, and a deterioration in ductility, while small eccentric columns fail in a brittle manner due to concrete crushing. The strain distribution in the damaged section still approximately follows the plane-section assumption, with crack propagation controlled by the initial crack face. Finally, a damage reduction factor model is developed, linking crack width to bearing capacity degradation, and the calculated results align well with experimental findings. This research provides experimental evidence and theoretical tools for assessing the load-bearing capacity of cracked arch bridges.