Seismic Reinforcing Design on Osaka Harbor Bridge
– Durable Design against the Most Credible Huge Earthquake –
Bridges / Infrastructures / Asset Management
Osaka City Japan, 2001-2008
The Osaka Harbor Bridge is located on Route 4 of the Bayshore Line of the Hanshin Expressway. The bridge is 980 m long, and the length of its center span is 510 m. The maximum height of its main truss is 68.5 m. Constructed in 1974, the bridge supports double deck traffic lanes. It is the third longest cantilever truss bridge in the world, following Forth Bridge in Scotland and Quebec Bridge in Canada.
A design review conducted after the 1995 Kobe earthquake included seismic response analysis, which indicated the possibility of buckling and/or yielding in main structural members in the event of the most credible earthquakes. In order to overcome the problems, re-designing work based on damage control design method was executed. Main design results include the adaptation of a so-called isolator, which is a kind of rubber support, for the longitudinal support of the double decks. This is intended to extend the natural period of the structure longer than the predominant period of an earthquake. It will reduce seismic forces. In addition, the work included replacement of bracing members in the lateral bracing and sway bracing with dumper type members that are effective in anti-seismic reinforcement. The bridge has been structurally renewed and is in service for daily public transportation.
