Montana: Bridge Deck Performance

Near the small town of Saco, Montana, three bridges were constructed less than one mile apart along the same highway corridor, Montana State Route 243. Because of their proximity to each other, each bridge experiences essentially identical demands from weather, traffic, and winter maintenance. To assess bridge deck performance, each of the bridges was instrumented then each bridge was fitted with a different type of reinforced concrete deck.

The instrumentation is primarily concentrated in a single driving lane of one 15 m span on each of the three bridges. Strain gages were placed in each bridge deck prior to casting the concrete. Three different strain gage technologies were used in each bridge: 35 Vishay foil strain gages bonded to reinforcing steel, 7 Vishay embedment-type strain gages suspended in concrete, and 16 Geokon vibrating-wire strain gages suspended in concrete.