The Long Term Structural Health Monitoring of Bridges in the State of Connecticut
by
John T. DeWolf
University of Connecticut, Storrs, Connecticut, U.S.A.
Coauthors: Josh K. Olund, Chengyin Liu, Alan J. Cardini

The University Of Connecticut and the Division of Research in the Connecticut Department of Transportation have been involved in monitoring both steel and concrete bridges during the past two decades. Approximately 30 bridges have been monitored, involving both short term studies and long term studies. The short term studies have been used to supply information needed in the evaluation of existing bridges; these have included evaluation of load carrying capacity and evaluations needed for planned renovations. The short term studies have also provided a basis for the development the current phase of the research involving the long term monitoring of a series of critical bridges in the State of Connecticut.

This paper will report on the installation of permanent monitoring systems on four different bridges in the State of Connecticut during the past decade. The monitoring systems have been tailored to each bridge, using sensors for strain, temperature, tilt and vibration. Monitoring is conducted on a continuous basis, with excitation provided by normal traffic loading. The bridges are monitored remotely from the University of Connecticut and the Connecticut Department of Transportation. Evaluation of the field data is being used to characterize the performance of each bridge and to provide information for long term structural health monitoring.

The paper will summarize key results from the monitoring of the four bridges. The bridges and monitoring systems are as follows:

• Post-tensioned, five-celled box-girder bridge with three unequal spans. The monitoring system includes sensors for temperature, tilt and vibration. Prior to installation of the monitoring system, the bridge was renovated because of significant cracking in the interior circular columns and in the box-girders near the interior supports. The data has been used to show how the bridge performs and to demonstrate that the cracking has been a result of differential temperatures.

• Large multi-span post-tensioned segmental box-girder bridge with temperature sensors. The bridge was selected because it is the largest box-girder bridge in Connecticut and because it had experienced significant cracking. As a result, the designers of the bridge recommended monitoring of temperatures to evaluate how differential temperatures influence the overall behavior. The data has been used to verify that the cracking is most likely due to initial support settlement.

• Multi-span, curved, continuous, double box-girder bridge with a composite deck. The bridge is supported by tall circular reinforced columns, and inspection has noted that there have been substantial cracks in these columns. The bridge has been monitored with temperature sensors, tilt meters and accelerometers. The results have shown that the cause of the column cracking is due to temperature variations.

• Multi-steel girder-bridge on the interstate system. The bridge is typical of many bridges in Connecticut. It is a three-span, simply-supported bridge, with a continuous deck. The bridge is being monitored with strain gages. The monitoring results are being used to determine load histories, the distribution of the loads to the eight girders, and the effect of the composite action.

This long term project was developed to learn how bridge monitoring systems can be used in the evaluation of the in-service behavior, provide information that can be used for the long-term structural health monitoring of each bridge, and to assist the Connecticut Department of Transportation in their management of the State’s bridge infrastructure.

Date received: November 15, 2005

Copyright © 2005 by the author(s). The author(s) of this document and the organizers of the conference have granted their consent to include this abstract in Atlas Conferences Inc. Document # carb-96.