Grand Avenue over Interstate 70, the Colorado River & Union Pacific Railroad
Glenwood Springs, CO
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The structural system for the vehicular bridge consists of three trapezoidal weathering steel box girders. The tapered sides minimize the width required at the tops of the piers for the bearings. Each pier consists of three octagonal shafts with no pier caps. This avoids the lengthy pier caps that would otherwise be required because the skew angle gets quite extreme at the northernmost piers.
As its south end Grand Avenue descends to the level of the street grid at Eighth Street. The vertical clearance available varies from roughly 14 feet at Seventh Street to barely 8 feet at the south abutment. In order to keep the structural depth of this section to an absolute minimum it is built as a full-width, 3’ thick post-tensioned concrete slab. The underside of the slab is coffered to minimize the weight of the slab as well as to give it visual interest for people using the space under the bridge. The edges of the slab are tapered to encourage the penetration of daylight into the space under the bridge. Users on the street below see only the thin edge, which makes the bridge seem amazingly thin and thus very light.
The structural system for the pedestrian bridge consists of two weathering steel rectangular box girders. The space between the girders sis occupied by multiple utility lines that cross the river. At the piers octagonal shafts pass outside of the box girders to provide visual continuity with the columns of the roofs over the overlooks at two of the pier locations. The overlooks are placed between the railroad and the river and on the centerline of the spa pool. The girders are supported by a concrete cross girder between the pier shafts. The arched soffit of the cross girder emulates the architectural features of the elevator tower.
The community's visual goal was to tie the nineteenth century spa buildings north of the river more tightly into the urban structure of downtown south of the river. With this in mind, all of the octagonal pier shafts on both bridges are oriented in plan so that their axes are parallel to the downtown street grid. As a further assertion of visual order, the upper halves of the piers are faced with the same red sandstone as the spa buildings and the railroad station. The red sandstone visually ties together the historic buildings on both sides of the river.
The city of Glenwood Springs limited the closure period between the demolition of the old bridge and the opening of the new vehicular bridge to the 60 day lull between tourist seasons. This required constructing the concrete slab at its south end within the 60 day period. The pedestrian bridge was required to be in service at all times, which required building the new pedestrian bridge in the very narrow gap between the previous vehicular and pedestrian bridges. These requirements significantly limited the design options available for the project.
Vehicular Bridge Length: 2300 ft., Width: 90 ft. Pedestrian Bridge Length:900 ft., Width: 14 ft.
Main Spans: Vehicular Bridge: 3 @ 330 ft. Pedestrian Bridge:
Project Cost: $48.6 million
Year of Completion: 2018
Project Manager and Landscape Architect: Jacobs Engineering Group, Inc.
Design Engineers: Vehicular Bridge: Tsiouvaras Simmons Holderness Pedestrian Bridge and Elevator Tower: Amec Foster Wheeler
Advisory Architect for Bridges and Elevator Tower: Frederick Gotteemoeller
Urban Design and Streetscape: James Leggit, Studio Insite
Owner: Colorado Department of Transportation
Photo Credits: To be supplied later