Fashion Island Boulevard Bridge

"Repairing Earthquake Damage"

What’s the best way to repair a California bridge after a devastating earthquake?

That was MWH’s task on the Fashion Island Boulevard Bridge in San Mateo, California (United States). The bridge had been damaged during the 1989 Loma Prieta earthquake.

The Project

The Fashion Island Boulevard Bridge was a 619-foot-long and 61-foot-wide concrete precast girder type bridge, supported on 36-inch octagonal concrete friction piles. These extended through soft (Bay Mud) soils.

MWH performed a geotechnical investigation for the seismic retrofit of the bridge. Geotechnical considerations for the retrofit included testing the structure’s response during seismic shaking. It also included evaluating the ultimate lateral, compression and uplift loads. New pile caps also were constructed.

To retrofit the bridge, large diameter steel shells were driven into the underlying dense soils. At the same time, concrete shells were developed for the existing and retrofitted structure.

MWH provided the following services to the project:

• Conducting a site reconnaissance
• Installing piezometers
• Reviewing available, published and unpublished soil, rock, geologic and seismic information
• Providing engineering analysis of the available existing field data and piezometers
• Preparing the analysis report
• Providing a final structural design.
• Supplying engineering support during the procurement and construction stages.