The Murray Morgan Bridge renovation reestablished a historic connection between the Port of Tacoma and the city's downtown.
The bridge was closed to traffic in 2007 and scheduled for future demolition, but a coalition of community stakeholders, with support from federal and state legislators, negotiated transfer of the bridge's ownership from the state to the city and secured funding for the $52.7-million project.
The design-build team rehabilitated and upgraded the bridge to current standards while maintaining the aesthetic qualities of the bridge, which is on the National Register of Historic Places.
The team reduced live loads by decreasing vehicular lanes to two from four. The abandoned lanes were converted to bicycle and pedestrian use. Dead loads on the three-span, 600-ft through-truss were reduced by using lightweight concrete. Structural repairs, including superstructure seismic enhancements, were incorporated to bring the structure into compliance with current seismic codes.
Meeting current American Association of State Highway and Transportation Officials' standards required sheave assemblies with bearings larger than those installed in 1913. Bearings are typically placed outboard of the sheave and attached to the bridge towers. The newer, larger bearings could not be installed per the original configuration—mounted directly to the tower column—because the column could not be modified to accept the larger bearings. The team conceived a unique sheave assembly that allowed the bearings to be placed inboard of the sheaves rather than outboard.
In returning the bridge to its original look, the design-build team pitted cost and schedule against aesthetics. To address much-needed strengthening of the truss chords, the design team developed a rod-and-anchorage system to reinforce the bottom chords. This approach proved economical because the construction team did not have to remove countless rivets and plates. It also had little impact on the structure's silhouette.
Murray Morgan Bridge Rehabilitation, Tacoma, Wash.
Owner City of Tacoma
General Contractor PCL Civil Constructors
Geotechnical Engineer GeoEngineers
Structural/Mechanical Engineer Hardesty & Hanover
Civil Engineer: Exeltech
Painting and Coatings: Purcell P&C