Hoan Bridge Hanger Force Measurement	Print    Inquire    847-965-7500

Problem
The Wisconsin Department of Transportation initiated a comprehensive project to inspect, test, and rehabilitate the Hoan Bridge after observing dramatic cracking of steel girders on the approach spans and other potential safety and maintenance problems. CTLGroup was part of the evaluation team.

Next Steps
As specialists in field instrumentation and testing, CTLGroup was retained by the prime consultant, Lichtenstein Consulting Engineers, Inc., to determine the existing forces in the hangers of the tied-arch span on the Hoan Bridge. Knowing the magnitude of existing hanger forces was necessary to calibrate a finite-element model used in the analytical evaluation of the bridge. In addition, the existing forces provided a snapshot of the load distribution among various hangers, thus identifying any unusual or inconsistent patterns that could signal structural problems in the span. A rehabilitation scheme would then include any needed redistribution of forces between the hanger or hanger elements.

Results
On the Hoan Bridge, CTLGroup used a vibration technique to estimate forces in 64 hanger cables (16 panel points; 4 hanger cables per panel point). The vibration data were recorded using a non-contact laser vibrometer, then analyzed to estimate forces in the hanger cables. These measured forces were then used to calibrate a finite-element model of the bridge and to evaluate safety and maintenance requirements for the tied-arch span.