Since the service life of concrete bridge decks designed by traditional procedures is often shorter than desired, their ability to withstand constant and heavy use in a variety of operating environments is of major concern. In a project recently completed for the Montana Department of Transportation (MDT), the relative performance of three bridge decks constructed with different concretes and reinforcing steel configurations was studied to help determine which deck offers the best performance over time. To achieve this objective, an array of strain and temperature instrumentation was embedded in each of the bridge decks prior to placing the deck concrete. The decks were tested under controlled live loads to characterize their structural behavior. The first set of such tests was performed immediately after the bridge decks were completed, and the second was conducted two years later. The long term performance of the three decks under environmental loads (notably, changes in temperature) was studied by continuously monitoring selected strain gages in each bridge, and by conducting periodic visual distress surveys and corrosion tests. In the data collected and analyzed from the live load tests and environmental response monitoring of the three decks, only subtle behavioral differences were observed. While some aspects of the response have been found to statistically differ between bridges and over time, the significance of these differences remains uncertain because the bridges are relatively young, and they only exhibit nominal signs of distress. The significance of these differences may become clearer under continued monitoring if substantial differences in deck durability and performance emerge over time. The analysis previously conducted generally served as a baseline for the relative condition of the three bridges before prolonged demands from traffic and the environment. A follow-on project to continue monitoring is needed to obtain long-term strain and temperature data to provide a more complete body of evidence from which to ascertain which deck design offers superior performance.

Note: This project was used as a case study by the provider of data logging equipment. View the case study