Spanning the Mississippi River, the Smith Avenue Bridge (also known as Saint Paul’s High Bridge) features large steel arches and post-tensioned steel tendons, key components in keeping forces in the arch balanced and structurally stable.
In 2017, a High Bridge preservation and re-decking project required cutting the steel tendons. The bridge’s owner, the Minnesota Department of Transportation, wanted to confirm that bridge movement wouldn’t be a problem. Barr worked with Kraemer North America, the project’s construction manager and general contractor, to design, install, and implement a near-real-time monitoring program. This compared actual bridge movements and strains to those modeled by HHA Consulting, Kraemer’s structural engineer for the project.
Our team installed over 50 monitoring prisms, 32 strain gage instruments, and radios on the bridge along with an automated motorized monitoring total station (AMTS) and solar power system on each shoreline. Every hour, each AMTS monitored 25 prisms from 100 feet to over 1,000 feet away.
During the 15-month project, we collected and analyzed nearly 2 million measurements, ranging from small movements caused by solar radiation of the steel arches to 5 inches of movement caused by cutting the steel tendons. These measurements were very close to the modeled estimates.