Walt Whitman Bridge Tower Finger Joint
– Monitoring and Rehabilitation
The Walt Whitman Bridge (WWB) is a long span suspension bridge and connects Gloucester, New Jersey and Philadelphia, Pennsylvania, carrying Interstate I-76 over the Delaware River. Tower finger joints on the WWB have been subject to constant impacts under heavy wheels, producing large vibrations and noise. As a result, the Fabreeka washers under the anchor bolts needed to be replaced frequently. CHI was retained by DRPA to investigate the causes of vibration/noise and develop rehab or replacement alternatives.
A variety of retrofit strategies were developed, and they included:
Replacing Fabreeka washers with steel washers
Increasing bolt tensions
Shimming of finger plates at the tower side
Using die springs in lieu of steel and Fabreeka washers
Lubricating the sliding finger plates in the suspend span
A few panels of finger joints were selected for verification tests in the field. CHI conducted the tests using various sensors, e.g. strain gages, accelerometers, video cameras, load cells, etc. Based on the test results, the alternatives that yielded the best performance was selected as the final retrofit option.
CHI’s monitoring platform integrates state-of-the-art sensors, and proprietary data acquisition and management system, allowing long-term, continuous, and high-precision monitoring of the strain, stress, deformation, vibration, etc. with greater flexibility to meet the needs of our clients.