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I-90 Dresbach Bridge



PROJECT CHALLENGES AND INNOVATIONS

Principal project challenges included providing the most durable structure type for long life with little maintenance, providing long spans over the main river channel to accommodate commercial river traffic, eliminating river impacts during construction for uninterrupted commercial and recreational river use, and minimizing environmental impacts to protect the Upper Mississippi River National Wildlife and Fish Refuge. The segmental concrete solution enabled the Minnesota Department of Transportation (MnDOT) to overcome these project challenges. Dual 508-foot main spans built from above resulted in only one pier in the main channel of the river while providing a commercial navigation opening larger than that required by the United States Coast Guard, maintaining river operations uninterrupted during construction, and minimizing impacts to the environment. The unmatched durability of prestressed concrete ensures the highest performance and longest lasting superstructure, saving MnDOT valuable maintenance dollars over the life cycle. The use of concrete allowed the community’s vision for their new landmark bridge to be realized with custom pier shaping and color treatment honoring the unique characteristics of the landscape and the community’s vision.

FIGG and MnDOT collaborated closely to exceed the already robust durability benefits of post-tensioned concrete segmental design.  The new bridge features stainless steel reinforcing in the deck, non-corrosive ducts, galvanized and epoxy coated anchorages, and the latest high-performance grouts for the post-tensioning system, and an innovative thin premixed polymer concrete (PPC) deck overlay at discrete wear areas such as expansion joints. In addition, a site-specific thermal study and finite element analysis ensured exceptional control of mass concrete placements, while force-pulse (Statnamic) dynamic load testing was used to most accurately determine pile capacity saving piling requirements and cost. The bridge design also includes accommodation for a future pedestrian bridge to be suspended beneath and between the eastbound and westbound structures. A unique catenary-suspension bridge design was developed to ensure structural capacity and for the inclusion of suspension anchorages in the current construction to accommodate the future bridge when pedestrian demand increases.

REASONS FOR CHOOSING CONCRETE

The new Dresbach Bridge demonstrates how concrete can be used to create a highly durable and beautiful long span bridge constructed within a sensitive environmental area, and under harsh winter conditions. Long 508’ main river channel spans are achieved using the post-tensioned segmental concrete balanced cantilever method with construction completely from above for the least possible river and environmental impacts during construction. The longer spans ensured the least permanent bridge footprint best preserving the river. Concrete for the bridge was sourced locally using local materials and local labor resulting in a boost for the local economy not possible with other structure types. The new bridge was delivered on budget and ahead of schedule and serves as a new landmark for the community while greatly enhancing the region’s transportation system and area mobility. In addition to ensuring the most durable and least maintenance new crossing for Interstate 90, the use of concrete allowed the implementation of context sensitive design as selected by the local Community.  A Visual Quality Advisor Committee (VQAC) was involved throughout the planning, development and design process to ensure a unique landmark bridge complimenting the environment. Located within the Upper Mississippi River National Wildlife and Fish Refuge, the bridge serves as a model for how a grand bridge structure can be developed to exist harmoniously with, and honor, the landscape and environment. Context-sensitive design inspiration came from this natural, picturesque landscape, blending functionality and aesthetics that considered the many different area vantage points, including the river, a rest area along the Minnesota Bank, the nearby United States Army Corps of Engineers (USCAE) Lock and Dam No. 7, and the surrounding forests and bluffs. The heavily-forested surrounding inspired unique pier shaping that represents the trees common in the old-growth forests through which the bridge passes.  Abutment texturing and project-wide tan coloration matches limestone outcroppings visible on the high Minnesota bluffs.

Project Details

Location:

Interstate 90, La Crescent, Minnesota

Owner:

Minnesota Department of Transportation

Engineer:

Figg Bridge Engineers, Inc

Construction Management:

Minnesota Department of Transportation

Contractor:

Ames Construction

Reinforcing Bar Fabricator:

CMC Rebar & Simplex Supplies

Rebar Placer:

J&L Steel & Electrical Services

Total Concrete Yards:

44,597

Reinforcing Tons:

4,412

Project Cost:

$82 Million