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Main Street over Stony Creek

Montgomery County, Pennsylvania

Rehabilitation

Owner:

Pennsylvania Department of Transportation

Engineer:

Transystems

Contractor:

JD Eckman

Installation:

August 2013

Determined to be structurally deficient, the original 159 year old structure on Main Street near the intersection of US RT 202, was in desperate need of rehabilitation in order to continue to carry 20,000 vehicles per day over Stony Creek. Since the structure was deemed a "contributing element" in the historic area, it was imperative that the structure be maintained rather than replaced. Built in 1854, the borough-owned bridge has been repaired many times and has a mix of different types of stone on the upstream and downstream sides.

After considering the options, it was decided that the structure should be strengthened and relined with a 37’-10" x 12’-11" plate structure, 76’-6" in length. PennDOT choose to specify a 3 gage, galvanized option designed to carry an HS-25 live load. The structure weighed over 700 pounds per foot and Contech Engineered Solutions knew from past experience that it would be difficult to handle and construct. At bid time, Contech received approval to offer an aluminum option, which weighed about 400 pounds per foot less. Even though the cost was a bit higher for the aluminum option, due to ease of handling and the shorter time to assemble, the low bid contractor went with the aluminum option.

"At bid time, we knew from past experience that the assembly of a 3 gage galvanized structure, weighing in excess of 700 pounds per foot, would be challenging," stated Dave Maugle, Executive Vice President with JD Eckman (JDE), the Contractor on the project. "We were pleased PennDOT allowed the aluminum option. We have worked with many Contech products over the years, but this was the first time we considered an aluminum plate structure of this size. We met with Contech, and they were able to provide us with the information necessary to address the risks associated with a project of this complexity. Even though the cost was more than the as-specified galvanized option, we chose to go with Contech’s aluminum SUPER-PLATE® option."

In spite of using a lighter weight material, the installation was challenging. There is 8’ of standing water under the bridge. A record amount of 23" of rainfall occurred in the previous month, and flash flooding occurs frequently in the bridge area. Since JDE was required to remove its working platforms daily, the lighter weight aluminum option shortened the overall assembly time, while also contributing to a reduction in operational risks. In order to give JDE the potential extra time they might need to coordinate a complex daily operation, Contech committed to and met an aggressive delivery schedule.

Due to a generous annular space between the existing structure and the SUPER-PLATE, JDE chose to build the structure within the existing structure. Assembly was completed utilizing custom made field tools and support jigs, in lieu of an assemble/jacking-in-place method. The technique was a success and the assembly was completed in just six days. To ensure the assembly went well, Contech provided on-site technical support prior to the assembly and on-site shape control monitoring during the grouting process.

"Contech saw us through all the details and proved to be a valuable partner in the execution of the work," added Maugle. "We will certainly consider Contech and its product options on future projects of this type."

The project also included rehabilitation of the stone retaining walls and an upgrade for the parapets to current impact standards. This phase of the project was part of a larger scope which included street scape and storm water improvements. The total project value was 20.8 million dollars.

 

Technical Description:

• Product: SUPER-PLATE®
• Span: 37’-10"
• Rise: 12’-11"
• Length: 76’-6"

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