Lessons Learned from Colorado’s Longest Direct Fixation Bridge
(Room Sagamore 6)
19 Sep 17
3:30 PM
-
4:00 PM
Tracks:
AREMA Technical Sessions- P&T
The North Metro Rail Line is an 18.5 mile electric commuter rail line currently under construction as part of Denver’s Regional Transportation District (RTD) FasTracks program that will provide transit service for travelers from Denver’s Union Station through Commerce City, Thornton and Northglenn to Highway 7 in North Adams County. A signature structure on this line is the Skyway Bridge, a 9,533’ curvilinear structure with 64 prestressed concrete girder spans that will become the longest bridge on RTD’s system and the longest bridge in Colorado. The Skyway Bridge presented several complex design challenges including post-tensioned integral straddle caps, rolling stock analysis to assure optimal passenger comfort, and rail-structure interaction analysis necessitated by continuously welded rail fixed directly to the concrete superstructure. To capture the rail-structure interaction a full 3-D non-linear finite element model incorporating the rail, direct fixation fasteners, and structure was created. A unique plastic-based analysis approach was utilized to accurately predict design loads on the substructures due to thermal effects and meet criteria regarding maximum gap developed in the case of a fractured rail. The design team investigated several techniques to reduce substructure loads and rail gap size; ultimately the final design utilized nearly 10,000’ of continuous direct fixation track without the need for intermediate expansion joints. This paper discusses the challenging design components of this complex structure and provides lessons learned and insight gained from extensive investigation of the interaction between structure and direct fixation track.