Three-Dimensional Modeling of Live Loads on Culverts

Soil-structure interaction analysis of culverts is typically conducted within two-dimensions, assuming the culvert and surrounding soil are in a plane strain condition. This is adequate for analysis of deeply buried pipes, but is a poor compromise for investigating the performance of pipes with a shallow cover subjected to live loads, where three-dimensional attenuation of the live load takes place both through the soil and the structure. In most cases evaluating live load effects in two dimensions leads to conservative designs, as the longitudinal distribution of load is underestimated. Recent advances in computational technology now allow full three-dimensional analysis of this problem, but there are many questions to be addressed in determining suitable soil models and other aspects of the problem. This paper reports on research into modeling of full scale live load tests on culverts. Important aspects of soil models suitable for three-dimensional analysis of culverts subjected to live loads are discussed. Shear failure and stiffness variation with depth are found to be important in modeling live loads.