Design of a Concrete Tied-Arch Bridge for California High-Speed Rail Requirements: Use of Vertical Hangers vs Inclined Hangers

摘要

When use of steel is unfavorable, a concrete tied arch bridge is a feasible and cost-effective structural system to support high-speed rails spanning a relatively long distance over existing features on the ground while providing minimum horizontal and vertical clearance requirements. In this paper, a systematic study was carried out to optimize the structural performance and design of a complex 236 ft long single span concrete tied arch bridge by investigating the effect of hanger configuration on the bridge behavior. Using both inclined hangers (network tied arch) and vertical hangers (Langer configuration), the bridge response was evaluated for static loads in addition to track-structure interaction and seismic requirements specified by the California High-Speed Rail project. As a part of this evaluation, the main structural member sizes, including the reinforced concrete knuckles, posttensioned concrete tie beams, reinforced concrete arches, and steel hangers were refined. A detailed 3D finite-element model of the bridge was developed to complete rail-structure interaction, static, dynamic, seismic, and construction stage analysis, given consideration to geometry, material, and boundary nonlinearities. Generally, the analytical results indicated that the network tied arch alternative is more beneficial than vertical hanger system by reducing the main member sizes, without compromising the structural performance and intended functionality of the bridge. It was also found that the sag effects, and thus the geometry nonlinearity in a network tied arch bridge are negligible due to short length of the hangers. Using the analytical results, design recommendations are also provided to satisfactorily design concrete tied-arch bridges.