Performance of two-dimensional analysis: Deteriorated metal culverts under surface live load

• Experiments on culverts were modelled using FE and design code approaches.
• Commonly used linear elastic FE models did not capture critical behaviour.
• Design software predicted forces in intact but not deteriorated culverts.
• FE models were used to predict linear elastic behaviour or provide an upper bound.
• Design code equations underestimated thrust forces in most cases.

As buried infrastructure assets reach the end of their service lives, better methods to assess these assets are required in order to optimize infrastructure budgets and management programs. As a first step towards developing these more accurate methods, the results of four currently available culvert modelling approaches were compared with the results of experiments on a deteriorated culvert as well as two buried culverts (one with significant deterioration and poor backfill, and one with limited deterioration and well compacted backfill) subjected to simulated vehicle loading. Two finite element analysis programs were used: CANDE, a commonly used software package specifically for culverts, and ABAQUS, a more robust general use package. Three different live load spreading factors were used with these programs to determine which one most accurately modelled the three dimensional live loading effects in two dimensions. The capacity of the culverts was also estimated using the design equations given in the Canadian and American bridge design codes. All the finite element models were unable to capture the non-linear behaviour of the deteriorated culvert with poor backfill as well as both culverts at high surface loading due to the use of linear elastic models. CANDE was found to provide very poor estimates of culvert diameter change but good estimates of culvert performance for the culvert with limited deterioration and well compacted backfill. ABAQUS could be used to predict culvert diameter change and thrust force with good accuracy in the linear elastic region or provide an upper bound estimate depending on the surface load spreading model that was employed. Both the Canadian and American design code equations underestimated the thrust forces in the culverts, suggesting that these approaches could be unconservative.

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