WSF Vashon Trestle Rehabilitation Project

The Vashon timber trestle rehabilitation project includes seismic retrofit and partial replacement of the existing timber trestle at Washington State Ferries Vashon island ferry terminal. The retrofitted portion of the trestle will be improved seismically for the 1,000-yr AASHTO event and will include the use of exterior steel batter pile frames and diaphragm strengthening through the use of timber and structural steel. The replacement trestle will be composed of a concrete superstructure with a steel plumb-pile substructure. The project was designed primarily using AASHTO, with the Washington State Ferries terminal design manual used as a supplement. Performance-based design methodologies were utilized with target performance objectives of fully operational for the 100 year seismic event and collapse prevention/life safety for the 1,000 year seismic event. This paper provides an overview of the project and discusses key design components.