5. A New Concrete Viaduct Structure

      Highly cost-effective, low noise and vibration, and seismic damage free structure is demanded today for the railway viaduct structure which is used as the successive overpass in urban area and in the high-speed railway. The Railway Technical Research Institute (RTRI) has developed a new concrete viaduct structure in place of the traditional reinforced concrete rigid-frame viaduct. The new viaduct structure consists of lightweight superstructures and high-rigidity high-damping pier structures. The superstructure is denominated as a "track-supporting girder" which supports vibration-isolated non-ballasted single-line tracks from directly underneath using separated single girders. The pier structure is composed of RC rigid-frame with diagonal steel braces and a steel panel damper (see Fig. 1).
      The track-supporting girder is made of single-track precast concrete structure with a hollow or a pi-shape section (see Fig. 2). This structure can reduce the unit-length weight of superstructure to half that of the rigid-frame viaduct (approximately 20 t/m).
      It was verified using a full-size girder specimen that structure-bone noise does not increase due to the reduction of weight of superstructure.
      It was also verified using a 1/2.5-scaled pier specimen that the transverse vibration caused by earthquake motions can effectively be controlled (see Fig. 3); the high lateral bearing capacity can easily be achieved; and the damage mitigation of concrete member against severe earthquakes can be realized.
      Based on these test results, design manuals for the new concrete viaduct structure and standard design drawings of track-supporting girders have been published. Using the new concrete viaduct structure, the construction cost can be reduced by approximately 15% compared with the traditional rigid-frame viaduct structure.
      This study was conducted with a government subsidy from the Ministry of Land, Infrastructure and Transport.

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