DO ANH TIEN

Stress characteristics of steel I girder with corroded thinning

Eiji Iwasaki

As a basic study for estimating the stress of the corroded thinning part, we propose a method of evaluating the stress of the lower flange with corroded thinning for the steel I girder bridge with corroded thinning on the lower flange. Firstly, we derive an estimation formula for the stress of the lower flange with corrosion thinning for non-synthetic girders (steel girders only) and synthetic girders (deck and steel girders) that receive bending moments. Based on the cross-sectional specifications of the steel I girder bridge with similar dimensions of the actual bridge used in this study, the relationship between the stress ratio before and after corrosion due to the residual corrosion rate is investigated. Finally, finite element analysis is used to clarify the validity of the estimation formula of the stress of the lower flange as well as the extent of the error that may occur. The findings obtained from this study are shown below.
It can be seen that the stress at the center of the span by FEM analysis converges to the value calculated from the estimation formula as the corrosion length increases, regardless of whether it is a non-synthetic girder or a synthetic girder. On the other hand, when the corrosion length is small, it can be seen that the stress at the corroded part becomes larger than the value calculated from the estimation formula. Also, when the residual ratio of the lower flange changes to 0.7, 0.5, 0.3, the error increases, but the convergence remains the same.
We found that the estimated value with the ratio of the corrosion length to the web height of 2.5 or less has a large error. Therefore, as a method to improve the accuracy of the estimation, correction coefficient for estimated value was examined and applied.