In November 2008, a heavily loaded barge battling strong currents collided with a bridge pier. The collision damaged the pier and caused misalignment of the swing span, which would no longer close properly.
Safety concerns forced the Massachusetts Highway Engineers to close the bridge to traffic. The engineers then designed a series of tests to evaluate the structural integrity and load capacity of the bridge. The tests involved static loading of the bridge deck and lateral loading of the piers.
GEO-Instruments provided the instrumentation system. Data had to be collected remotely, since personnel were not allowed on the bridge during the tests. The instrumentation included:
- Electrolevel tilt-beam sensors
- Automated vibration monitors.
- Data acquisition system.
- Wireless internet connections.
Using a barge-mounted manlift, GEO-Instruments installed beam sensors directly onto the damaged pier. Two discreet vertical beam sensors were mounted on the east and west ends of the pier. Four sets of horizontal and vertical beams were mounted on the north and south faces of the pier. As loads were applied, the beam sensors would report any movement in the pier as a change in tilt.
A data logger recorded readings from the beam sensors at one-minute intervals during the tests. The vibration-monitors had self-contained loggers to record readings in real time.
Both the data logger and the vibration monitors had wireless connections to the internet. A web-based GEO-Instruments server processed incoming readings and posted them in graphic form on a web page within three minutes of being recorded.
The static load test was conducted in 4 phases over a 5-day period. To apply the load, a crane barge placed jersey barriers onto the bridge deck. The fully loaded deck was able to hold 96 jersey barriers, equivalent to 185 tons. Engineers were able to view near-real time readings during the tests using an on-site PC and a web browser.
The tests proved that the bridge was safe for traffic and it was reopened. The bridge was finally replaced in 2012.
Hines Bridge was closed after being struck by a barge.
Beam sensors were installed on four faces of the pier to monitor possible deformation during load testing.
A barge-mounted crane is placing jersey barriers on the bridge deck. A barge was also used during installation of the instruments.
The collision damaged a pier and caused misalignment of the swing span.