Metal Culvert Response to Earth Loading: Performance of Two-Dimensional Analysis

Abstract

The results of finite-element analyses conducted before and after testing of a 9.5-m span low-profile metal arch culvert are presented here. A two-dimensional procedure that models the elastic-plastic response of both structure and soil during backfilling has been used. A plasticity-based procedure to provide an upper bound for the effect of soil compaction on metal culvert response during side filling is introduced and used in the analysis of field response. The procedure involves application of passive earth pressures after layer placement to simulate the highest values of residual horizontal earth pressure. The pretest and posttest analyses are compared with measurements of field response previously published by Webb et al. Predictions for culvert deformation and bending moments generated during backfilling were excellent. The new procedure to include the effects of compaction during construction was effective in capturing culvert peaking during placement of the side fill and increases in bending moment. Both pre- and posttest predictions for deformation and moment successfully captured the culvert response during burial and the effect of backfill soil density. The posttest predictions include consideration of the top-loading applied during placement of the side fill. The predictions of deflection follow measured values during application and subsequent removal of those temporary surcharge loads. Estimates of soil stresses acting normal to the external surface of the culvert were shown to be close to those measured in the field. The analysis indicates that shear strength is fully mobilized in wedge-shaped zones of the backfill adjacent to the culvert. Those zones diminish in size once backfill is placed over the crown. The residual horizontal earth pressures that are modeled during compaction act to reduce the size of the plastic zones.