GONZALEZ PORRAS ALFREDO ISAI

Study on Buckling Strength of I-Girder Subjected to Negative Bending with Corrosion Thinning on the Lower Flange

岩崎　英治

Aging steel infrastructure in Japan, particularly bridges built during the economic growth period (1955–1973), faces significant deterioration due to corrosion. Among various structural components, the lower flanges of I-girders subjected to negative bending moments are particularly vulnerable to buckling failures caused by corrosion-induced thinning. This study evaluates the impact of localized corrosion on the buckling strength of these bottom flanges, aiming to provide insights for maintenance prioritization.
The research employs finite element analysis (FEM) to simulate elastoplastic buckling behavior under varying degrees of corrosion. Corrosion severity is represented using two parameters: (α), which defines the remaining flange thickness, and (β), which describes the extent of the corroded area along the flange length. Simulations were conducted across seven different width-to-thickness ratios (R) to assess the sensitivity of buckling resistance to these parameters.
The results demonstrate that flange thickness reduction (α) has the most critical impact on buckling resistance, leading to a significant loss of structural capacity due to the reduction in stiffness. In contrast, the longitudinal extent of corrosion (β) influences resistance to a lesser extent, acting as an amplifying factor rather than a primary cause of instability. Moreover, steel plates with high slenderness ratios (R ≥ 0.7) experience the most severe reductions in buckling capacity, making them particularly vulnerable to failure.
These findings underscore the need for targeted maintenance strategies, emphasizing preventive measures for structurally slender elements. Future research should focus on refining corrosion modeling techniques and incorporating full-beam simulations to enhance the accuracy of predictive maintenance frameworks. Establishing empirical equations to quantify buckling resistance loss based on corrosion parameters would further support efficient resource allocation for infrastructure maintenance in Japan.