On the morning of March 21, 1982, a severe earthquake of a magnitude of 7.1 on the Richter scale hit Urakawa-oki or off Urakawa, southern part of Hokkaido Island in Japan. It is reported by the Japan Meteorological Agency (JMA) that the hypocentral depth was 40km and the highest JMA seismic intensity was 6 at Urakawa town. Shizunai Bridge, located near the epicenter, sustained serious damages to 6 pier columns out of 8. Very heavy cracks occurred at 2 pier columns (Piers-3 and 6), and medium to minor cracks were observed at 4 pier columns (Piers-2, 4, 5, and 7). This paper briefly describes an outline of the Urakawa-oki Earthquake, damage features of Shizunai Bridge, and results of a dynamic response analysis of Shizunai Bridge, which was conducted for investigating the causes of damages to the bridge. Two different analytical models are employed for the dynamic analysis. The first is a model of the overall system involving the entire parts of the bridge, although the second is a model of Pier-3 which was most seriously injured. In the both cases, structural responses to seismic motions in the direction transverse to the bridge axis, are computed. In an analysis for the overall model, two abutments, 8 piers, and 9-span girders are considered as a lumped mass-spring system. Surrounding soils above the bedrock are also included in the system, and non-linear characteristics of soils are considered. All of structural parts made of steel and reinforced concrete are assumed as elastic members. From the analysis for the overall model, it is concluded that responses (ratios of acting forces to design forces) of Piers-3 and 6 (supporting two ends of continuous girders) which sustained heavy damages are extensive comparing with those of the other piers, and that horizontal forces analyzed for Piers-3 and 6 are higher than 2 times their design horizontal forces, respectively. Next, in the analysis of Pier-3 model, non-linear characteristics of the reinforced concrete pier column are considered. From the analysis, it is concluded that plastic state will extensively develop at a section of 4.0m above the bottom of the column, which well explains the actual behavior of Pier-3 during the earthquake. (Author)

  • Supplemental Notes:
    • Seismic Research for Highway Bridges (US-Japan Program) is a collection of Papers Reprinted Directly from the United States-Japan Cooperative Program on Natural Resources (UJNR) Panel on Wind and Seismic Effects; and the Proceedings of the US-Japan Seminars on Repair and Retrofit of Structures, 1979 to 1984.
  • Corporate Authors:

    Pittsburgh University, Pittsburgh

    Department of Civil Engineering
    Pittsburgh, PA  United States  15261

    National Science Foundation

    1800 G Street, NW
    Washington, DC  United States  20550
  • Authors:
    • IWASAKI, T
    • Hagiwara, R
  • Publication Date: 1984-6

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  • Accession Number: 00394010
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Jul 31 1985 12:00AM