Mechanical Behavior of a Composite Box Bridge Used for 40 Years

摘要

Recently, the importance of maintenance has been recognized by many civil engineers because of a lot of aged and deteriorated infrastructures in Japan. On the one hand, various composite structures have been developed, especially the composite box girder bridge, which consists of a U-shaped open cross section of steel and bridge deck of reinforced concrete, is often being constructed nowadays due to its construction cost efficiency. Kando-bashi is a composite box girder bridge composed by a reinforced concrete deck and a steel open cross section girder, and has been used for about 40 years. The purpose of this study is to provide basic information for the maintenance of the composite box girder bridge, in which the global behavior of the bridge is investigated using an on-site loading test, and also the slip behavior of the shear connector is investigated using a indoor loading test with a part cut out from the bridge. In addition, the remaining strength is predicted through non-linear finite element analysis, using for Kando-bashi, where lack of web thickness as corrosion is assumed near the shoes and the live load provided by Japanese Standard of High-way Bridge (JSHB) is taken into account. From the results, it can be concluded that the bridge functions in the same way as a composite girder though passes 40 years after use, and the remaining strength hardly decreases even if the web thickness near the shoe decreases by 40% due to corrosion.