Performance Monitoring of Jointless Bridges - Phase III

The Vermont Agency of Transportation has seen an increase in the number of jointless bridges constructed over the past several years but engineers often struggle with how best to approach the design. It is felt that jointless bridges offer a number of advantages over conventional bridges, but without a formal design protocol these benefits may not be fully realized. In order to develop adequate design standards it is necessary to obtain and analyze comprehensive performance data pertaining to field monitored structures in order to maximize design efficiency. Integral abutments, which are shallower depth structures, are constructed away from the edge of an obstruction whether it is a railroad, highway, or river. In the case of a wet crossing the bridge's abutments are constructed further up the stream bank eliminating the need for cofferdams. Besides the initial construction savings experienced by eliminating cofferdam construction, considerable cost savings are also realized in the construction of the abutments, reduced maintenance, the elimination of expensive bearings and limiting the degree of environmental impact. A brief literature search conducted early in the formation of the Agency's Integral Abutment Committee (IAC) found that many engineers for various state DOTs continue to design jointless bridges "because they work" without monitoring the bridge's performance or answering any design questions with validated research data. In order to understand how these bridges respond to dead, live, and impact loads and how they respond to the environment, performance monitoring will be performed over the course of three years after construction has been completed. Prior to the opening of the bridge, load testing of the bridge shall be conducted using the design vehicle, vehicle placement or locations and live load combinations which were used in design. Finite element analyses shall be conducted to compare the results from the load tests for each bridge to the design calculations.