Figure 14 - Rendering of New Indian River Inlet Bridge looking towards the Northeast. One of the primary objectives behind the design of the new structure was driven by the community. The existing structure provides spectacular views of the Atlantic Ocean while crossing it. The community did not want the new structure to obstruct this view in any way and so the new bridge is designed to allow open views to the ocean. It’s slender and open form does not overpower the pristine nature of the surrounding landscape. (Illustration courtesy of AECOM). Figure 15 - The current construction progress as of the end of August 2009 includes 80% of the 36" square prestressed concrete pile foundations have been driven to 1800 ton capacity; pylon footing and tower construction has begun (photo of Northeast Pylon footing); and installation of temporary falsework used for the cable stay superstructure erection over land has begun. (Photo courtesy of AECOM).

The design-build team of Skanska USA Civil Southeast and AECOM USA are currently designing and constructing the new SR1 Bridge (Figs. 14 and 15) over the Indian River Inlet for the Delaware Department of Transportation. The design-build team started in September 2008 and the new 2,600' long cable-stayed bridge will be opened to traffic by April of 2011. The cable-stayed main span unit is comprised of 3 spans: 400'-950'-400'. Approach spans are prestressed concrete Bulb-T girders. The new bridge will carry four lanes of traffic with shoulders and a pedestrian sidewalk on the Atlantic Ocean side of the bridge.

Overall design of the bridge is about 75% complete. The wind tunnel testing, coastal hydraulics, scour, and geotechnical analyses are all complete. Foundation static load testing is also complete for the 1,800 ton capacity 36" square prestressed concrete pile foundations. Installation of all production piles and the four (4) pylon footings will be completed by the end of September 2009. Cable-stay erection will begin in March of 2010. Skanska is building the bridge from both sides of the inlet simultaneously.

Several innovative design-build features have led to both an economical and aesthetic structure:

• The cable-stayed superstructure consists of cast-in-place (cip) concrete edge girders with both precast and cip transverse floor beams. The portion of the cable-stayed structure over land will be constructed using falsework and includes the precast floor beams. The portion of structure over the inlet will be constructed using a form traveler and cip concrete. Floor beam spacing was limited to 24' on centers to reduce the deck thickness to 8½". Minimizing the deck thickness in turn significantly reduced the dead load forces, which in turn reduced the size of the stays, demand on the pylons, and size of foundations.


• The edge girders and semi-harped cable-stays remain in a vertical plane and the edge girders deviate around the pylons using a compression and tension strut system. This system helps minimize the out-to-out footprint of the structure.


• Maintaining a vertical plane of cable-stays and optimizing the pylon cross section so that the downward stay force acts along the center of gravity of the pylon cross section allowed the use of single mast pylons with no cross struts above or below the deck. The single mast pylons without heavy cross struts significantly improve the aesthetic value of the bridge as well as improving the overall constructability and maintainability.

The design theme was simple for this structure: Maintain unobtrusive views of the Atlantic Ocean and don’t overpower the quiet beach community with a massive structure. The design-build team has created a simple and slender structure that is being embraced by the community. An open wave-shaped pedestrian railing; semi-harped stay arrangement replicating sails; blue cable stay sheathing; and subtle blue lighting at night will keep the bridge from interfering with the natural beauty of the surrounding areas.

Owner: Delaware Department of Transportation
Design-Build Team:
Skanska USA Civil Southeast (Design Builder)
AECOM USA (Lead Design)
AECOM Asia (Erection Engineering)
International Bridge Technologies (Bridge Design)
RWDI (Wind Tunnel Testing)
S&ME (Geotechnical)
Parsons Brinckerhoff, Inc. (Independent Design Review & CEI)
FINLEY Engineering Group, Inc. (Construction Engineering)
Freyssinet, LLC (Cable-Stay Supplier)