Structural Monitoring Saves Shawnee County Bridge

Structural Monitoring Saves
Shawnee County, Kansas, Over $500,000

This bridge was built in 1914 over the Waukarusa River. Visual inspections indicated that the center span was bending. A load limit of five tons was placed on the bridge which prevented school buses from using it. Because the alternate route was impassable in snowy conditions , the bridge was scheduled for replacement. Structural Integrity Systems, LLC, was asked to monitor the structure to determine if the bridge should be destroyed. The monitoring system placed on the structure consisted of a load transducer under each arch and a tilt monitor on each pier. Vehicles of known loading were then monitored as they crossed the bridge. There were no plans and the engineers had assumed the bridge was a span structure. However, the data gathered quickly indicated that the structure was going into a compression response and that the bridge was actually a filled concrete arch. The loaded tandem axle in the photo weighed 42,800 pounds, which is 26% over the legal load limits set by the state of Kansas. The transducers all reacted well within acceptable parameters and no further bending of the center span was observed. It was determined that the bend in the center that had initially caused the concern had probably been there since the construction of the bridge. The load limits were removed from the structure and it will remain in service for years to come.

The graph to the right shows the loading of the center arch in microstrain. The structure's dynamic response was exactly linear.

The graph below is the real time response of the loaded tandem axle crossing the center span and causing it to go into compression. The numbers on the y-axis are simply reference numbers that were peculiar to that particular transducer. The important fact is found in the difference between the maximum and minimum of the curve. The difference of 486 times 0.84 equals 408 microstrain. A very acceptable response for this type of structure. If there are questions concerning these graphs, please do not hesitate to contact us.

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Sundial Bridge California
Rolling Bascule Florida
Royal Park Bridge Florida
South Broadway Overpass Kansas
US 24 Pottawatomie County Kansas
Shawnee County Bridge Kansas
Kemper Arena Construction Missouri

Please call and talk to us concerning the monitoring of bridges, buildings or other structures.
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Monica L. Svaty
Chief Executive Officer

Karl J. Svaty, Jr., PE, SE
President/Manager

316.634.1396
(NEW TELEPHONE NUMBER)

http://www.structuralintegritysys.com

U.S. Patent No. 5,421,204
U.S. Patent No. 5,507,188
Canadian Patent No. 2,163,653