A Century-Old Link in Downtown Des Moines
The Grand Avenue Bridge spanning the Des Moines River serves as a major link between the downtown Des Moines business district and East Village. Approximately 7,600 vehicles utilize it each day, making it one of the area’s busiest bridges.
Originally built in 1918 and last rehabilitated in 1968, the bridge was 441-feet long, 66-feet wide with eight-foot wide sidewalks on each side. It was a reinforced concrete arch bridge, which became structurally deficient and severely deteriorated over time.
Bridge Replacement Signals Massive Undertaking
Construction of a new four-span, 446-foot long, 54-feet wide pretensioned, prestressed concrete (PPC) beam bridge began in December 2016, following demolition of the previous structure.
It supports three lanes of traffic with a westbound bicycle lane and 14-foot wide sidewalks on both sides. A painted metal panel arch façade and LED accent lighting enhance its appearance.
Unique features and design challenges include:
- Leaving portions of the existing abutments in place to minimize disturbance to floodwalls and levies
- Predrilling abutment piling through the existing abutments and driving new piles into bedrock. The predrilled holes were backfilled with concrete
- Prototypical semi-integral abutment details were developed to account for the pile fixity caused by the rigid connection/incorporation into the existing abutments
- Developing aesthetic details with the City of Des Moines and an architect to create a new signature Des Moines River bridge
- A non-standard deck cross section with raised pedestrian sidewalk
- Adding beam lines under the raised pedestrian sidewalk to allow a snooper truck to inspect the underside of the bridge during future bridge inspections
- The additional sidewalk load resulted in non-uniform beam reactions, requiring careful analysis to determine bearing pad sizes
- Incorporating over 20 separate utility conduits
- Designing the bridge to account for inundation with water overflowing the barrier rails
The Iowa Department of Transportation (DOT) let the project, and all plan submittal dates were met. The engineer’s estimate of probable cost for the project was $8,612,304.00 with an estimated bridge cost of $7,749,615.00. The actual bid price for the project was $9,060,752.68 with an actual bridge bid cost of $8,379,396.23.
In November 2017, the bridge opened to one lane of vehicular traffic in each direction with pedestrian traffic on the south sidewalk. Substantial project completion is anticipated to continue during winter 2017/2018, and the project is slated to be fully complete in summer 2018.
Shuck-Britson and Snyder & Associates made the project possible by teaming to provide the following services:
- Development of project concept statement
- Preliminary bridge and roadway plans
- Hydraulic analysis and documentation
- Final bridge and roadway design plans
- Limited construction review services
- Coordination and development of aesthetic details
In addition, the team also rapidly responded to issues that arose during construction, including pile driving inquiries and utility placement.
Click here for additional information from the City of Des Moines.