Olsson’s engineers who worked on Abraham’s Bridge took on a much higher calling than simply designing a bridge.
The bridge needed to connect the four buildings of the Tri-Faith Commons: Three houses of worship representing the Abrahamic faiths – Temple Israel (Jewish), The American Muslim Institute (Islamic), Countryside Community Church (Christian) – and the Tri-Faith Center that serves as a hub for educational events.
But Abraham’s Bridge connects more than buildings. The circular bridge was created to cultivate a sense of community between those who share different religious views.
Olsson’s Nebraska Roads and Bridges team was tasked with designing the bridge. But before the team could start, two challenges needed to be solved involving Hell Creek, which runs through the property. First, the pedestrian walkway would go through an active wetland mitigation site. Second, three bridges had to be constructed within an urban Federal Emergency Management Agency (FEMA) regulatory floodway that was under a Conditional Letter of Map Revision (CLOMR).
Hell Creek is an almost fully urbanized watershed in the heart of Omaha. Because of federal and local regulations, our design had to comply with an outdated FEMA floodplain map and meet “no-rise” requirements for both current and pre-Sterling Ridge conditions. We also had to prove our design would not adversely impact neighbors. We accomplished this by creating a hybrid hydraulic model that combined the higher flows from the regulatory model with the revised geometry of the CLOMR model.
We also worked with the U.S. Army Corps of Engineers (USACE) to make sure our design would not impact the wetlands forming along the banks of the creek.
The design of the bridge (1,440 feet in diameter) used specialized geometry and tight tolerances, especially on the bridge spans. Our team determined that a unique prefabricated steel system would satisfy the tight tolerances needed to maintain a consistent circular shape. We used a modular steel superstructure system with curved hollow structural sections. This system enabled us to maintain a small structural depth that minimized obstructions in the regulatory floodway and met the “no-rise” requirement for new structures.
This design is more cost-effective and more visually unique than a standard steel truss design. The walking surface of the bridge and the lighting bollards are made of easy-to-maintain, sustainably sourced timber.
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