Fatigue Evaluation of Bridge 4654

Project summary:

The objective of the proposed work will be to estimate the residual fatigue life of the subject bridge under projected traffic and to assess the effect on the residual life of removing large trucks from the traffic. The work is planned to take place over the summer of 1998, specifically to begin as soon as possible and to be completed within 90 days of the start of contract. In order to accomplish the objectives, we will perform a visual inspection of the underside of the superstructure, particularly noting the condition of the stringers, floorbeams, and the tension chords of the trusses. We will instrument one floorbeam with at least four strain gages and one tension chord with at least two strain gages. We will monitor these strain gages while trucks of known axle weights cross the bridge during short periods of traffic closure. We will then monitor the gages for a period of three days during open traffic flow. We will rationalize the measured strain data by performing an analysis of the floor system and, if necessary, the truss. We will use established methods to perform the analysis of the residual fatigue life. The deliverables will include a report documenting the results of the instrumentation and monitoring, the structural analysis, and the fatigue evaluation. The residual life will be estimated based on projections of current traffic and on conditions where large trucks were no longer allowed on the bridge.