Sound Transit, the agency that owns and operates the light rail transit system in the Seattle, Washington, area, is extending light rail transit service to east King County over the existing Homer M. Hadley Memorial Bridge. The East Link Extension Project presents unique technical challenges: the movements of the floating structure pose problems for a fixed rail track and, although there are examples of similar projects on cable-stayed and suspension bridges, there is no precedent for light rail on a floating bridge. A novel method—the curved element supported rail concept—has been developed to accommodate the multidimensional movements that exist at the joints between fixed and floating portions of the bridge. This paper presents a discussion of the results of full-scale tests of a portion of the overall system. The purpose of these tests was to assess the efficacy of several key components of the new system in advance of full-scale prototype testing. Overall, the system behaved as it was designed to. The tested components provided the necessary movement capabilities; stresses did not exceed 10% of yield; and deflections, which could cause alignment issues and poor rider comfort, were well within operating requirements. The tests revealed that the design of the guardrail, and in particular the way in which it is fastened to the system, is one of the most important design decisions facing the successful implementation of the system. In addition, the tests helped refine the testing needs and requirements for the follow-on prototype testing program.
A light rail passenger transportation system is being built in Seattle, WA, USA, that traverses Lake Washington over an existing pontoon bridge. The water level in Lake Washington changes throughout the year. This causes rotations of the transition spans, which are needed at each end of the bridge to carry traffic between the fixed, land-based structure, and the floating structure. This paper explains a novel method, the Curved Element Supported Rail (CESuRa) system, that provides rails with the ability to undergo joint rotations at the ends of the transitions spans without risk of damage, while maintaining full vertical support of the track across the joint. The geometric characteristics on which it depends for proper operation, considerations that must be accounted for when using the system for other applications in the future, and an overview of the implementation of the system on the floating bridge are discussed. Keywords Light rail transit Á Floating bridges Á Pontoon bridges Á Expansion joints Á Rail hinge Á Track bridge
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