Remaining Strength Evaluations of Steel Girders with Corrosion near Supports and their Reinforcements

Abstract

In Japan, many steel railway bridges were constructed during the period of rapid economic growth in the 1960s. Now, as over 50 years have passed, the condition of these aging structures has become conspicuous, and a major social problem. In particular, the deterioration and damage due to corrosion in steel plate girder railway bridges with open deck system is becoming pronounced. Nevertheless, the remaining strength evaluation and the methods of reinforcing corroded structures are not always sufficient. Therefore, the purpose of this study is to propose an analytically-based evaluation method, and a reliable measure of reinforcement in the field of steel railway bridge maintenance. The following is noted: 1) Regarding the shear capacity of plate girders with corrosion near supports, the remaining strength depends on the condition of the corroded surface of each component of the member, such as a web or a vertical stiffener. Also, according to the form and degree of corrosion, the fracture mode also changes from the buckling of web to the buckling of cross-shape columns which consisting of the web and vertical stiffener. The result shows that the corroded web has more effect on the shear capacity than the vertical stiffener. 2) Regarding situation of separation between the web and bottom flange due to corrosion near supports, the remaining strength is found to deteriorate more rapidly than in the Case 1 above when the separation area lengthens to more than that of the sole plate area. 3) To enhance the remaining shear capacity in the Cases 1 and 2 above, the load bearing capacity can be improved dramatically by unsophisticated attachments applied as reinforced members.