Modified load rating procedure for cast-in-place reinforced concrete box culverts in Louisiana

Many cast-in-place reinforced concrete box culverts in Louisiana were built using outdated standard plans originated from the 1940s and updated in the 1970s. These culverts often yield low load rating factors when evaluated using current AASHTO procedures. Despite this, they performed satisfactorily overtime with minimal signs of distress. Simple 2D frame element models are commonly used for structural analysis of typical box culverts due to their ease and speed. However, they tend to produce more conservative load rating results compared to complex modeling techniques like 3D plate element models. A parametric study was conducted using 120 3D finite element culvert models in various configurations, along with corresponding 2D frame element models. Correction factors were developed to correlate moment values from 3D and 2D analyses. Field testing of representative culverts was also performed to validate the analytical models. The study considered two types of wall-slab connections: pinned and moment connections. The results indicate that using moment connections, an at-rest lateral earth pressure coefficient, k _o of 0.50, and the 3D-2D correction factor, yields more realistic load rating values that reflect field conditions. The study’s findings were used to develop guidelines for load rating reinforced concrete box culverts in Louisiana, which can also be applied to similar culverts elsewhere.