Hood Canal Bridge
Seattle, WA
One half of the 7,900 ft long floating concrete box pontoon bridge across Hood Canal in Washington sank during a very severe storm. The bridge, which was originally reinforced concrete, but had been previously reinforced by post-tensioning, had a draw span near its midpoint to allow ocean-going vessels to pass. The entire west side of the bridge failed progressively during the night of the storm. In the investigation SGH used an analytical model that included the bridge pontoons, the cables, and the hydrodynamic coefficients of mass and damping of the pontoons in water. Modeling considered torsional and bi-directional flexural behavior of the concrete box pontoons. A spectral analysis was performed for water waves consistent with sea spectra.
Service Provided:
Investigation
Supporting Capabilities:
Structural Engineering
