Assessment of Dynamic Load Allowance for Buried Culverts

Most traditional research on buried culverts has looked at live load distribution through soil onto buried culverts without due attention to the dynamic amplification of moving loads. The few studies that looked at the dynamic amplification of buried culverts idealized the load-soil-culvert problem using a plane-strain assumption. Under such conditions, the finite area axle loads are erroneously modeled as strip loads acting over the entire width of the culvert. In this study, the plane-strain assumption is removed and the load-soil-culvert system is modeled and analyzed as a three-dimensional problem. Dynamic load allowance (DAF) was determined from field measurements, two-dimensional finite element method (2-D FEM), and three-dimensional finite element method (3-D FEM). The 2-D and 3-D FEM models resulted in average DAFs of 1.10 and 1.03, respectively. The average DAF calculated from field measurements and the American Association of State Highway and Transportation Officials (AASHTO) recommended formula are 0.973 and 1.30, respectively. Overall, the AASHTO DAFs are the highest and the field DAFs are the lowest. The plain strain assumption adopted in the 2-D FEM models resulted in DAF values that are higher than the 3-D FEM and field evaluated DAFs. The DAF calculated from three-dimensional models is the closest to the field measured DAFs.