EARTHQUAKE DESIGN AND CONSTRUCTION OF TAL COMPOSITE BRIDGE

The recent lessons of structural damages occurred to a number of bridges during 1995 Hyogo-ken Nanbu Earthquake make a new bridge construction more expensive and time consuming because of the high standard of earthquake resistant design. The new expressway construction (the 2nd Tomei expressway) mainly crossing over deep valleys requires many tall bridge piers. Therefore it is required to develop the new technology which takes place of the conventional RC hollow pier. The new design concept of steel pipe-concrete composite bridge pier exhibits not only high seismic resistance in effect of ductile steel pipe and spiral high strength strand, but also a rapid construction method. In this paper the earthquake design by the scaled model tests as well as the construction practice of the tall composite bridge pier are described. The results and conclusions are follows: The experimental M-Φ relation of the composite piers showed higher deformation performance than the conventional RC hollow bridge pier. In pseudo dynamic tests the composite piers had a stable seismic behavior even after the ultimate state. And although the deformation exceeded maximum peak, the residual displacement after the earthquake was relatively small. The analytical moment – curvature relationship of steel pipe – concrete composite piers showed lower deformation performance than the experimental results. The main reason of the low performance of the analytical models is due to the ductile steel pipe and high strength spiral strand, which cannot be coped with in the model. The results show that the contribution of steel pipes to concrete should be taken into account in order to improve the analytical methods for design. The new construction method (namely Hybrid Slipform Method) on the composite bridge pier provides an appropriate solution for rapid construction and reduction of the skilled labor