EVALUATION OF STEEL BRIDGES USING IN-SERVICE TESTING

Highway bridges often exhibit higher strengths than indicated by AASHTO rating procedures. This is because the code is inherently conservative and is intended to be applied to general situations. A more appropriate approach is to incorporate field observations in the rating process. A field measurements (weigh-in-motion) system is capable of providing all pertinent data on the loading and response of highway bridges. The data collected include measured stresses and girder distribution factors in addition to truck weights and volumes. The data are then incorporated in a working stress design rating or in a reliability-based safety evaluation of bridge members. Results from an example site indicate high safety levels despite the large numbers of permit vehicles allowed.