I-90 Track Bridge – Development and Implementation of a System to Carry Light Rail Vehicles on to a Floating Bridge

The Central Puget Sound Region’s transit agency, Sound Transit (ST), is planning to install light rail transit (LRT) tracks on the I-90 Homer Hadley floating bridge as part of the 14-mile long East Link project. Placement of light rail across the floating bridge, the first of its kind, presents unique challenges. The structural system is subject to dynamic, multidimensional movement of the bridge deck at the existing expansion joints, due to changing lake elevations, vehicle traffic loading, wind, waves and, for extreme conditions, the breaking of anchor cables, all of which were addressed in the design. Development of a unique and elegant solution required the collaboration of a team consisting of track engineers, special track work fabricators, structural engineers and research specialists, from the U.S. and U.K., all working with construction experts, to take the project from concept through installation.