Field Monitoring of Integral Abutment Bridge in Massachusetts

Integral abutment bridges are increasingly being used to eliminate undesirable bridge joint effects on the long-term performance of bridges. Although many states use this type of construction, common design guidelines are lacking, and nonuniform limitations on integral abutment design are imposed by different agencies. Data from the field monitoring of an existing three-span integral abutment bridge in central Massachusetts are presented. Resulting data are valuable in evaluating existing design provisions and understanding structural behavior. The results presented for a 16-month period of monitoring include recorded ambient temperature from -4°F to 99°F (-20°C to 37°C). Longitudinal movements induced by thermal expansion and contraction of the bridge are consistent with temperature changes. However, earth pressure cell data indicate that the maximum pressures generated behind the abutment walls occur in early spring. Lower pressures measured in the summer indicate some dissipation of soil pressures with time. Longitudinal displacement measurements taken during 2-week periods included variations that approached the magnitude of seasonal changes. Although fairly significant abutment movement has been recorded to date, there is no clear indication that the abutment piles have yielded. Field monitoring will continue, and the results from this study will be used to calibrate a detailed finite element model of the bridge to validate current integral abutment bridge design practices.