Ultimate Limit State of Deep-Corrugated Large-Span Box Culvert

Limit state design requires independent assessment of both load and resistance. Although much is known about the live and dead loads that may act on box culverts, there is no known measurement of the resistance (or capacity) at the ultimate limit state. The objective of this study is to present results from a full-scale experiment conducted on a buried, deep-corrugated, large-span box culvert under controlled laboratory conditions the first conducted to its ultimate limit state. The box culvert had a 2.4-m rise and 10-m span (7.9 x 32.8 ft) and was fabricated from steel plate 6 mm thick with corrugations 150 mm deep at a 400-mm pitch (0.24 x 6 x 16 in.). The box culvert was backfilled to a minimum cover depth of 0.45 m (1.5 ft) with densely compacted well-graded sand and gravel. Tandem-axle loading was then applied by an actuator until an ultimate limit state was attained. The ultimate limit state of the box culvert involved the formation of plastic hinges at the crown and shoulders at a total applied force of 1,100 kN (250 kips). The force required to reach the ultimate limit state was 1.8 times larger than the factored design tandem-axle load from the AASHTO bridge design specifications. Similarly, the factored resistance at the ultimate limit state was 1.7 times larger than the factored CL-625-ONT tandem-axle load from the Canadian highway bridge design code.