Center Activities

Design and Strengthening of Highway Bridges

by M. Flett

On March 14, 1996, Dr. Kazuhiko Kawashima, professor of structural and earthquake engineering at the Tokyo Institute of Technology and formerly on staff of the Public Works Research Institute, presented a seminar at the University at Buffalo entitled "Impact of the Hanshin/Awaji Earthquake on Seismic Design and Seismic Strengthening of Highway Bridges."

His lecture began with an overview of the damage caused by earthquakes in 1923, 1946, 1948, 1964, 1978 and 1982 and how the Japanese code governing bridge design changed to mitigate such damage. It was discovered that during the 1982 Ukaowa-Oki earthquake, for example, the Shizunai Bridge experienced shear column failure caused by the termination of the main column reinforcement at mid height coupled with inadequate anchor length. A chronological survey of the recent improvements to the Seismic Design Manual for Repair and Reconstruction was also presented. The goals of design specifications for earthquakes of various magnitudes were outlined and descriptions of pile damage caused by earthquakes were given. The methods used to prevent liquefaction were briefly described. With regard to the 1995 Kobe event, Dr. Kawashima focused on the failure of reinforced concrete piers and the current three year program to strengthen more than 27,000 vulnerable piers. He also described the disadvantages of steel bearings, including the fact that they limit a structure's lateral movement. In summary, the Kobe experience has led Japanese bridge designers consider a shift to a ductility design from the seismic coefficient design method. Kobe has also shown the importance of including an assessment of a structure's importance in design and retrofit, and the need to evaluate the near field ground motion for earthquakes with shallow focal depths.

Following Dr. Kawashima's lecture, Dr. Yozo Fujino, a professor in the Bridge Structural Unit of the University of Tokyo, presented a brief talk describing his project on the optimal allocation of earthquake induced damage in elevated highway bridges. The project includes the development of a database showing damage to such bridges and a method to show the relationship between bridge damage and response for economical and efficient design and retrofit procedures.

Dr. Kawashima and Dr. Fujino were part of a four-member team who visited NCEER to discuss seismic isolation system hardware. (see photo) While at NCEER, they presented seminars, toured the seismic laboratory and discussed various topics related to seismic isolation with NCEER researchers at the University at Buffalo.

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Last modified January 8, 1996