Strength evaluation of prestressed concrete bridges by dynamic load testing

The load rating of a bridge can be obtained by means of field load testing. The dynamic load allowance or impact factor is one of the parameters used to establish a bridge's flexural capacity during the rating evaluation process. The focus of this study centered on comparing Bridge A7957's dynamic load allowance obtained by experimental and analytical methods proposed in three different design and evaluation codes. To attain this goal, Bridge A7957 was instrumented with accelerometers at different locations. For different dynamic tests, the spans' response was measured with the accelerometers and a laser vibrometer. The dynamic load allowance was obtained experimentally and analytically using current design and evaluation codes. The impact factors obtained analytically resulted in larger values compared to the experimental results. This difference might have repercussions in the strength evaluation results of bridge structures.