Which culvert type relies on the stiffness of its own material to resist loads?

• A. Embankment
• B. Rigid Culvert
• C. Cast-in-place Concrete
• D. Frame Culverts

Answer: (B)

A culvert that relies on the stiffness of its own material to resist loads behaves as a rigid shell. Its walls are designed to be stiff enough that they carry the earth and hydraulic pressures with minimal deformation, so the structure itself resists bending and settlement rather than needing extra support from surrounding soil or a separate frame. This means the culvert’s load-carrying capacity comes primarily from the material’s stiffness and the geometry of the culvert wall.

Other options don’t fit this behavior. An embankment-type culvert depends largely on the surrounding backfill and compacted earth to transfer loads, so the surrounding soil carries part of the pressure. Frame culverts rely on a supporting frame or skeleton to carry loads, not just the wall’s stiffness. Cast-in-place concrete is a construction method for making structures, not a culvert type by itself, and doesn’t specify the load-resisting mechanism in terms of material stiffness.