Corrosion Detection Used on PA Bridge

MONDAY, JULY 29, 2019

Announced last week, a historic Pennsylvania bridge will be the first in the U.S. to use an electrically isolated tendon system (EIT), which helps to detect corrosion on post-tension tendons.

The Coplay-Northampton Bridge—a 1930s era bridge between Lehigh and Northampton counties—was selected by the Federal Highway Administration and the Pennsylvania Department of Transportation, through a project search to find where the EIT could best be tested.

Lehigh University’s Department of Civil and Environmental Engineering and Dywidag Systems International plan to monitor the EIT’s effectiveness throughout the project. The technology has already been used in Europe.

About the Technology

While EIT technology can be used to monitor breaches in a corrosion protection system, it can also be used for quality control during construction.

By using the EIT to record electrical impedance measurements (the measure of opposition that a circuit presents to current when voltage is applied), condition of ducts can be monitored throughout the life of the steel.

The process also allows for the monitoring of the tendons’ conditions as well, without ever having to tamper with the structure itself. This is achieved by pulling an electrical terminal out of the anchorage to measure impedance.

The technology has reportedly already been demoed on the project and caused minimal changes to current construction practices.

“The use of the demo EIT technology did not have an adverse effect on the project schedule or budget,” said Larry Franko, project manager with Pennoni Associates, which is also the construction manager and inspector for the bridge replacement. “I predict in the future this technology should be considered for every pre-stressed and post-tensioned project.”

About the Bridge

Also known as the Chestnut Street Bridge, the structure was built in 1930 by Whitaker and Diehl (Harrisburg, Pennsylvania). As described by Historic Bridges, the bridge design features a concrete open spandrel deck arch with fixed and approach spans. The main span is 214 feet long, while the structure reaches 1,124 feet.

In total, the bridge encompasses three main spans and four approach spans, in addition to a 1,032-foot-long viaduct that consists of three reinforced-concrete deck girders, three open spandrel arches and a steel Parker thru truss.

The bridge was rehabilitated in 1958 and 1998.

The Project

According to Northeast Prestressed Products (Pottsville, Pennsylvania), the project is slated to cost $33.5 million and be completed sometime in 2020. (Work on the demolition and rebuilding of the bridge already kicked off in 2017.)

NPP will be providing the prestressed beams for the project; AECOM will serve as the project’s architect and engineer; and Trumball Corporation is serving as the contractor.

Once completed, the new structure will include a three-span continuous bridge with pre-stressed bulb tee girders and four splices along the span. Totaling five girder lines, each line will be post-tensioned and grouted with four tendons per line. A composite cast-in-place concrete deck may also be added.


Tagged categories: Bridges; Construction; Corrosion; Corrosion protection; Demolition; Department of Transportation (DOT); EIT Technology; Federal Highway Administration (FHWA); Infrastructure; Infrastructure; NA; North America; Program/Project Management; Technology

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