SATO Masakatsu Kawasaki Steel Corpn., Res. and Development Center, Senior Researcher, 研究開発センター, 主任研究員
IKEDA Shoji Yokohama National University, Dept. of Civil Eng., Professor, 工学部, 教授 (60087228)
UJIKE Isao Utsunomiya University, Dept. of Civil Eng., Research Associate, 工学部, 助手 (90143669)
NAKAJIMA Akinori Utsunomiya University, Dept. of Civil Eng., Associate Professor, 工学部, 助教授 (70164176)
SATO Ryoichi Utsunomiya University, Dept. of Civil Eng., Associate Professor, 工学部, 助教授 (20016702)
The composite plate girder bridges, in which the concrete floor and the steel girder monolithically works, are very popular as bridges of 20 to 50 meters in span length, because they possess good structural characteristics and are economical. Beyond 50 meters in span, however, they are not always economical and the deck type composite truss or inverted arch bridges will be advantageous, instead. But there are only a few composite truss bridges in the world at present and no composite arch bridges can be seen as yet.
The present investigation deals mainly with the deck type composite truss bridge through both experiment and analytical computation and is partly extended to the deck type composite inverted arch bridge, the latter being a bridge where a shallow long composite plate girder is strengthened by an inverted steel arch chord attached underneath. In the composite truss bridge the shearing force transferred between the upper steel chord and the concrete floor slab is not distribute
d so evenly as in the composite plate girder. In the composite arch bridge the upper chord with the floor slab shows a behavior,similar to that of a continuous composite plate girder which are elastically supported by intermediate piers and, furthermore, it is subjected to the axial compression transferred from the arch member underneath, presenting a more complicated structural behavior. For the experiment, three models of parallel chord truss, two of curved chord truss and five of inverted arch, all being. 2.4 meters long in span. They are mainly characterized by the variation in distribution of the shear connectors. The loading points were changed in each specimen, and finally the specimens were statically loaded to fracture. On the other hand, a specific program for electronic computer was developed for the analysis. It consists of three parts. Firstly, the concrete floor and the steel upper chord are divided at the panel points, and the elements of the steel chord and those of the concrete floor are respectively connected by springs. The elements of the steel chord and those of the concrete floor are connected by shearing springs, which correspond to the shear connectors. Secondly, the forces to be introduced to the steel elements of the upper chord are obtained by the plane structural analysis program. Thirdly, the detailed distribution of stresses in the concrete floor was obtained by a plane FEM model, where the forces obtained by the above-mentioned analysis for the upper chord are applied. The experimental results were in fairly good agreement with the analytical results. Many useful findings were obtained from the present investigation, such as the fact that in the case of truss bridge, concentrated arrangement of shear connectors is preferable, while in the case of arch bridge, distributed arrangement is more desirable. Less