Performance Evaluation of Reinforced Concrete Box Culverts

Summary

MnDOT has 909 cast-in-place reinforced concrete box culverts (RCBCs) with assigned rating factors based on the load at the time of design and the visual condition; the inventory rating factor for many of the RCBCs is less than 1.0, but these values were not determined via calculations or computational analysis. The focus of this study was to develop a load rating decision guide based on pertinent culvert attributes to implement load rating calculations for the RCBC inventory. Guidance was developed based on data and results from field testing and 3D finite element modeling (FEM) of 8 culverts, which led to calibration factors (CF) deployed in conjunction with 2D FEM of 31 additional culverts to extrapolate performance trends. Refined load rating factors were computed for the entire subset of 39 RCBCs using AASHTOWare BrR output, 2D FEM results, and live load values reduced by the CF, which translated 2D FEM live load results to an equivalent 3D system. All 39 culverts had refined inventory and operating rating factors greater than 1.0 for all live load truck types (HS-20, EV2, and EV3). Recommendations and guidance for calculating refined Load Factor Rating (LFR) rating factors of qualified RCBC in the inventory were developed for six culvert classes based on construction type (W or C) and fill depth (h < 5 ft, 5 ? h ? 8 ft, h > 8 ft). The refined LFR rating factors were all greater than 1.0 and were higher for C-type compared to W-type culverts.