Evaluation of actual yield strength in existing steel bridges using miniature compression test

This study investigates the applicability of the miniature compression test (MCT) for evaluating the yield strength of existing steel bridges. Preliminary tests were conducted to compare standard tensile tests with MCTs, confirming that the latter can reproduce the characteristic yield behavior, including upper and lower yield points. Material tests using MCT specimens extracted from existing bridges revealed that the measured yield strength was approximately 1.1–1.2 times higher than the specified minimum yield strength. Based on these results, a preliminary empirical correction factor of 1.084 was derived for the investigated material to convert the MCT results into equivalent tensile yield strength. Furthermore, structural performance was evaluated by applying the corrected yield strength to load-carrying capacity calculations. The results indicate that the influence of yield strength on load-carrying capacity differs between positive and negative bending regions, with a more pronounced effect observed in the negative bending region. These findings demonstrate that the MCT provides a practical and reliable method for strength evaluation of existing steel bridges.