Field Inspections and Monitoring of Continuous Deck Slabs on Prestressed Concrete Bridges for Development of Refined Details

Abstract

Expansion joints are used in bridges to allow for the unrestrained movement of the superstructure. However, due to the need for frequent maintenance, continuous deck details have been developed to replace them. This study evaluated the current detail Alabama Department of Transportation (ALDOT) uses to make the deck slab continuous at pier bent locations (termed closed joints) in prestressed girder bridges instead of using expansion joints (termed open joints). The study inspected five bridges across Alabama to assess the performance of the in-service detail. The inspected bridges varied in properties, including the span and overall lengths, skew angles, girder types, ages, and environments. Based on visual observations, the study found that the factor that most affected the visual performance of the deck was the detailing and tooling of the construction joint. The main damage observed at these closed joints was due to traffic wear and did not cause structural concern. To evaluate the behavior of and the demands on the closed-joint detail further, the study then monitored a bridge for a year. The behavior of both open and closed joints were monitored. The demands and movements at the girder ends were captured during this period, with a focus on the effects of thermal demands. The measured rotations from the monitored bents were similar in magnitude regardless of the detail used for the joint, indicating little to no rotational restraint was provided at the closed joint. The rotations measured from field monitoring indicated that using the AASHTO design values for rotation from thermal gradients will work for future design. For recommending values for future design, demands from live load and time-dependent effects were superimposed using guidance from AASHTO.