One of the many Texas Engineering Landmarks in celebration of Texas ASCE’s Centennial: 1913-2013 “Engineering a Better Texas.” Visit them all!
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Arapaho Road Bridge, ASCE Texas Section Outstanding Civil Engineering Achievement (OCEA) Award 2007
The town of Addison knew it didn’t want a "typical" highway bridge over the highly congested Midway Road. Despite their tight budget ($5 to $6 million) the town hoped for a landmark structure. A design competition between three short-listed firms provided the town with several unique designs. URS’ winning concept (presented via 3-D computer renderings and videos) depicted a structure that utilized twin steel pipe arches to support a prestressed U-beam superstructure. Architectural enhancements and specialty lighting created a visually stunning bridge, while the innovative engineering approach (using standard materials and construction methods as much as possible) enabled construction with minimal impacts to the Midway Road commuters below.
The 1,575 ft. long Arapaho Road Bridge is the signature piece of a two-mile extension of Arapaho Road. It carries four lanes of traffic and is a model of innovation for standard pre-cast concrete and materials. The bridge’s deck was constructed with pre-cast/pre-stressed U-beams and deck panels and is suspended by a series of steel rope hangers which attach to the arches and cast-in-place concrete diaphragms. The design is also notable for its use of round pipe for the arch rib, painted blue to tie the bridge into the town of Addison’s most famous public art piece: a sculpture called “Blueprint of Addison.” The use of round pipe is not only stylistically valuable, it also provides a high strength arch with good capacity against buckling and eliminates the need for lateral bracing.
Prestressed U-beams are typically used in Texas highway bridges to span up to 120 feet. Transport lengths of bridge girders are also usually kept below 150 feet. Therefore, the designers specified a spliced U-beam of 85-ft. long sections, temporarily supported in the median of Midway Road. By ultimately supporting the superstructure from the arch ribs, these U-beam sections would easily span the required 170 feet. The beams and the cast-in-place transverse diaphragms were designed for the temporary conditions as well as the final configuration and consideration of hanger replacement or loss.
The steel pipes were fabricated using induction bending and the arch pieces were erected in two pieces overnight prior to being set and spliced together. Designed to be self-supporting during construction, eliminating the need for temporary bracing, the pipe arch-ribs accommodated the change in forces during the hanger stressing as well as support the deck under normal loading conditions and hanger replacement or loss. The arch ribs were also designed for global buckling, local buckling at the hanger points, and second order buckling effects considering ovalization of the pipe.
Once the diaphragms and deck were cast, hangers were installed and stressed, lifting the bridge off its temporary bent.
The use of standard U-beams and deck panels allowed the construction to proceed without much disruption to the traffic under the bridge. Though intermittent overnight road closures were used for the erection of the arches, beams and deck panels.
The Arapaho Road Bridge was constructed in 18 months (actual completion in July 2004) and opened to traffic in January 2006 (remember: it was only a piece of the Arapaho Road extension project). The entire structure was constructed for $5.26 million, well within Addison’s budget. (Though specialty lighting on the arch span and roadway lighting along the length of the deck added another $700,000 to the bridge’s cost.)
Arapaho Road relieves an estimated 11,000 vehicles per day from Belt Line Road without any additional congestion at the Midway Road intersection. The aesthetic theme of Arapaho Road Bridge unites the two areas of Addison, and creates a striking gateway into the town’s restaurant district.
Records:
Owner- City of Addison, TX
Engineer/Contractor- URS Corporation, Cliff R. Hall PE
BRIDGE FACTS (source: (
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* 14 spans combine for a total length of 1575 feet
* The blue arches are three feet in diameter and 170 feet long
* The crest of the arch rises 52 feet over Midway Road
* True arch design with a suspended, four-lane roadway
* The roadway is supported by 18 2.5-inch diameter cables, which vary from 12- to 30-feet in length
* Sound walls reduce the noise impact on adjacent properties
* More than 220 lights on the bridge enhance visibility and security
* Final construction phase includes three pocket parks with a lighted hike-and-bike trail
* Landscaping will include more than 600 trees and shrubs
AWARD WINNING!
2006 NCSEA Excellence in Structural Engineering Awards Program Merit Award, Bridges and Transportation Structures
American Council of Engineering Companies of Texas: Eminent Conceptor Award for Engineering Excellence and its Gold Medal Engineering Excellence Award.
ASCE Texas Section Outstanding Civil Engineering Achievement (OCEA) Award 2007
PCI Journal: In 2006 PCI Journal named Texas Concrete Company precaster for the Best Bridge with Spans Greater than 135 Feet
FURTHER READING:
Structure (joint publication of NCSEA, CASE, SEI) “Arapaho Road Bridge Blends Steel Arch with Prestressed Beams” (
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URS “Arapaho Bridge” (
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GSI Highway Products “TEX-TUBE ELLIPITCAL BRIDGE RAIL” (
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Taste This Addison “Arapaho Pedestrian Trail” (
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