The Foss Waterway Bridge was one of the final links connecting the City of Tacoma’s Waterfront Industrial Park to downtown Tacoma, Washington. The Washington State Department of Transportation, Bridge Owner and Engineer, designed the bridge in two units. The western part is a two-span cast-in-place post-tensioned concrete box-girder bridge. The main unit is a two-span cable stayed, cast-in-place post-tensioned concrete bridge.

As a requirement of the project, VSL completed testing three full scale stay cable specimens. The cables tested were 6-24, 6-44 and 6-63 strand stays. Testing, which was carried out by CTL in Chicago, was performed in accordance with the Post-Tensioning Institute’s Recommendations for Stay Cable Design, Testing and Installation. After successfully undergoing 2 million load cycles at 160 MPa stress range, each specimen was subject to static ultimate loading. All three specimens easily passed the test requirements showing that VSL’s Stay Cable Systems, which use greased and sheathed monostrands, have very high fatigue resistance and excellent anchorage efficiency.

VSL also provided installation of the post-tensioning and Stay Cable Systems. The cable stayed portion of the bridge has a 107 m main span with a 101 m backspan. It is supported by two planes of cables attached to two identical pylons. The two vertical planes of cables are aligned with longitudinal girders on each edge, and with crossbeams at 4.6 m on center supporting the roadway. A total of 44 cables (containing from 24 to 63 15.2-mm monostrands) are typically spaced at 9.1 m centers.

The system uses VSL Monostrand Cables made of greased and extruded PE sheathed strand subsequently injected with cement grout. The stay cables were installed and stressed with 1,700 ton rams by VSL after completion of the superstructure and pylons.