Finite Element Analysis of a Low-Profile Steel Culvert with Field Verification

In the first part of this study, an ARMCO multiplate, low-profile, steel culvert with rib stiffeners on the outside was instrumented for strain and deflection measurements. Measured strains were converted to stresses, moments, and thrusts based on the assumption of non- composite action between the rib and plate. Deflections were computed from bench mark measurements by reducing them to rectilinear coordinates. Soil deflections were measured using four rod extensometers placed at selected locations around the culvert. Measurements were recorded during backfilling and, later, during live load testing. Composite and noncomposite moment calculations showed a noticeable tendency towards composite action as the backfill height exceeded the crown level. A lower degree of composite action was observed at the crown as opposed to the haunches. Deflection measurements indicated that the culvert displaced to the south as a result of placing the backfill material on the north side first. The finite element computer program CANDE was used to analyze the soil-culvert system in the second part of this study. The structural backfill material was modeled using Duncan's soil model which uses hyperbolic relations to express the elastic modili that relate increments of stresses to increments of strains. The soil parameters for the Duncan soil model were chosen from the CANDE material library for a similar soil. The ability of CANDE to predict the actual behavior of the culvert was examined. Comparison between the analytical and experimental results indicated that CANDE predictions are slightly conservative, and hence, are satisfactory from a design point of view. Also as part of this study, a computer program (PREP) was written for the purpose of facilitating the input procedure to CANDE, including an automatic mesh generation feature.