TYLin served as a Prime Consultant for the Sound Transit E360 Guideway Bridge project in Bellevue, Washington.
Delivered under a design-build contract, TYLin oversaw the final design for a two-mile segment of the overarching Sound Transit East Link Extension. The USD 225 million East Link Extension expands a local existing light rail system to connect the cities of Bellevue and Redmond, two major city centers.
Scope of work included the design of a 4,600-foot elevated guideway, track and special trackwork, and a pedestrian bridge over SR 520 to connect the Overlake Village Station to the Microsoft campus.
TYLin optimized the design of the Sound Transit E360 Guideway Bridge to develop a more cost-effective aerial structure and utilize low-cost, high-resilience rail fasteners to reduce potential noise and vibration. This innovative approach benefits project stakeholders by preserving the right-of-way for future improvements to the adjacent SR 520 highway corridor, including the construction of a future highway off-ramp under the guideway.
As Lead Designer during the bid phase, TYLin also led the team to develop an innovative redesign of the Overlake Transit Center. This resulted in the preservation of two acres of potentially developable land immediately adjacent to the transit center and a series of pedestrian bridges.
- TYLin successfully managed diverse stakeholder interests to deliver the program.
- Project challenges included bridge construction adjacent to a major highway in a metropolitan area with multiple road crossings, including a complicated overpass through a large intersection.
- The aerial guideway structure consists of four parallel wide flange girders ranging from 74 to 100 inches deep and 31 spans measuring 125 to 182 feet long. Typical spans are 95-inch girders spanning 140 feet.
- TYLin’s use of both precast, prestressed, stay-in-place deck forms for the guideway structure and offsite fabrication minimized the number of road closures, increased the quality of the finished product, and expedited construction.
- TYLin’s optimized design minimized the number of foundations required, resulting in the elimination of five 9-foot shafts and a 65-foot-long post-tensioned straddle bent.