Tacoma Narrows New Bridge

Seismic Evaluation & Design

The new Narrows bridge opened to traffic on July 16, 2007, four weeks early and $114 million under budget.  The bridge is parallel to and south of the 1950 Narrows Bridge. It carries four 11-foot-wide lanes of eastbound traffic toward Tacoma. The left lane is a high-occupancy-vehicle (HOV) lane, the two center lanes are general purpose lanes open to all traffic, and the right lane is an add/drop lane that extends across the bridge to the Jackson Avenue exit. In addition, the bridge has a 10-foot right shoulder for disabled vehicles and a 10-foot barrier-separated bicycle/pedestrian lane.

The concrete towers, which are 510 feet high, and caissons are designed for a second deck (either road or light rail) to be added in the future. The deck is 5,400 feet in total length, with a 2,800 feet main span.  SC Solutions was responsible for the following tasks:

• Development of 2 global models,
• Implementing construction sequence,
• Evaluating the seismic performance of the caissons,
• Creating a simulation of a sequence of the implementation of the second set of cables and a second deck which allowed design engineers to evaluate various construction alternatives quickly and efficiently.