Community Center Drive/112th Ave. Overpass

Submitted by: Flatiron Constructors Inc.

As winner of this year's American Concrete Institute's Award of Excellence in Construction, this project to connect the city of Northglenn went far beyond the expectations of both city officials and the community.

With I-25 separating the east and west sides of Northglenn, existing bridges at 104th and 120th Ave. experienced heavy traffic congestion, making it difficult for residents to get from one side of town to the other.

Flatiron made many key decisions on this project, resulting in a bridge that has become a landmark for the Northglenn community.

The project team chose a three-sided box girder without a top slab for several reasons, including increased stability over I-girders, two webs and a clean trapezoidal shape.

To create a flowable concrete mix for pumping down one web and into the bottom flange, the team used a high-range water reducer that achieved a nine-in. slump without sacrificing strength. The finished product is a high-quality girder, with a smooth finish and no voids or cracking.

Flatiron also constructed more than 15,000 sq ft of concrete block-face MSE retaining walls, which enable a reduced span length and bridge cost. The running bond pattern of typical concrete block MSE walls creates a uniform and repetitive look.

Flatiron carefully selected the ashlar pattern provided by the Allen block. Although more difficult to construct, it provides a pleasing appearance across large surface areas.

Bridge abutments incorporate cast-in-place concrete pilasters along the wingwalls. These pilasters - with their gold-anodized aluminum sphere mounted on top, architectural lighting and ceramic tile facing - provide a focal point for the bridge. The wingwalls extend forward from the front face of the abutment to form an angled hide wall for the girder ends. The decorative railing and details formed into the bridge face provide visual interest for the I-25 traffic below.

Project Team

Owner: City of Northglenn
Engineer: Sear-Brown
General Contractor: Flatiron Constructors Inc.
Major Subs: Slaton Bros., Ground Engineering, Nationwide Rebar, Rocky Mtn. Structures, Concrete Express, Rebar Coating & Fab, Ready Mix Concrete Co., Aggregate Industries

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