Load Testing and Rating of Cast-in-Place Concrete Box Culverts

One of the largest items in the bridge inventory for many states is culverts, and cast-in-place reinforced concrete box culverts constitute a sizeable portion of the overall culvert inventory. In Louisiana, most of these culverts were constructed using old standard details. Following current load rating procedures for these culverts often yields unacceptable load rating factors, even though their performance is acceptable with no signs of distress. The discrepancy between calculated load rating and observed performance of the culverts is investigated for eight selected culverts by field live load testing and finite element modeling. Each culvert was instrumented using a 48-sensor structural health monitoring system before a loaded truck was driven on the culvert along three different load paths to collect field data. Three-dimensional (3D) finite element (FE) models were calibrated using the recorded field data, and an HL-93 design truck and 10 legal trucks such as Type 3-3 were used to load the calibrated FE models to obtain culvert specific load rating factors. Acceptable rating factors were obtained for all eight culverts. The rating methodology, rating factors, and recommendations for rating culverts are presented in this paper.