ABSTRACT
In Japan, a lot of civil structures were constructed during the period of rapid economic growth in the 1960s. Now, over 50 years have since passed, the aging of these structures has become conspicuous and a major social problem. In particular, for many steel railway bridges with open deck system, deterioration and damage due to corrosion is becoming obvious. Partial repairs and reinforcement as well as total replacement of girders have taken place in recent years, but it cannot be said with certainty that these measures have been selected after proper, quantitative evaluations of the remaining strength of the girders. That is to say, the remaining strength evaluation method of corroded structures is not always sufficient. In light of recent socioeconomic conditions, there is an even more pressing need to establish streamlined, economically viable methods for maintaining these bridges.
One phenomenon that requires maintenance is local corrosion of the upper flanges under sleepers. Figure 1 shows that the coating on upper flanges under sleepers wears more easily and is more susceptible to dampness than other parts due to the train load acting almost directly through the rails and sleepers onto the girders. As a result, local corrosion progresses and leads to the collapse of bridges. Many studies on ultimate strength of plate girders (Basler & Thurlimann1), Moriwaki et al.2),3), Fujino4), Komatsu et al.5), etc.) had been conducted by experiments and analyses. However, none of them were taken account of local corrosion despite the fact of taking into account corrosion under the sleepers is vital toward accurately evaluating the remaining strength of this type of steel railway bridges. Therefore the purpose of this study is to propose concretely the remaining strength evaluation method for the maintenance of steel railway bridges. Steel railway bridges with open deck system. https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315207681/cd556cd4-4dcf-4efe-8e29-56fc67b8bfbd/content/fig180_1.jpg"/>
As an indication of their progress, regarding the pure bending, this study clarified that the horizontal buckling strength can be calculated by the equation of Basler, and the torsional buckling strength can be calculated with a high degree of accuracy by the equation suggested in this study. And load bearing capacity in terms of both pure bending and local loads was independently evaluated, parameter analyses that focus on the proposed strength interaction curve of plate girders subjected to the pure bending and local loads simultaneously could evaluate the remaining strength of plate girders.
In addition, this study verified the applicability of this method from existing experimental values and analytical values obtained through FEM to clarify that ultimate strength can be evaluated with a high degree of accuracy.
