Saving Scotland's Busiest Bridge

The world’s most extensive bridge monitoring system has been installed on Glasgow’s Kingston Bridge so that the engineers can prevent collapse during a long-term program of strengthening and repair. The bridge, considered state-of-the-art when completed in 1970, has exhibited severe deterioration and must also be brought up to new European codes. With five traffic lanes on each of twin concrete segmental structures, carries 154,000 vehicles per day and cannot be closed for long periods. The owner agency, Strathclyde Regional Council, augmented its staff with consultants to determine and correct the bridge’s flaws. While interim measures were undertaken, a monitoring system was devised that includes both surveys and electronic instrumentation that measure 39 critical points and transmit the data off-site for constant computer analysis at intervals varying from 15 seconds to 15 minutes. Included are 36 Linear Variable Differential (LVDTs) to monitor local horizontal and vertical movements, 128 platinum resistance thermometers installed at different depths in the concrete, and two meteorological. Other instruments measure stresses and strains in the concrete and the loads developed at the expansion joints. Rehabilitation will cost £36 million and will not be complete until 1999.