Response of Long-Span Box Type Soil-Steel Composite Structures during Ultimate Loading Tests

Soil-steel composite structures are getting more popular in recent years. With the introduction of more sophisticated structures such as box culverts with flexural stiffeners, the review of largely experience based design models became inevitable. The paper presents the ultimate loading part of full-scale testing conducted on corrugated steel box culverts. Structures with two different spans of 14 and 8 m and different crown stiffness were investigated using different cover depths. The tests indicate that the response of the structure to the depth of the cover is not linear. The structures become more vulnerable to applied loads as the soil cover decreases. The increase in the load-bearing capacity with increasing soil covers is linear, which agrees with the theoretical models. The crown stiffening, however, is more effective under shallow soil covers. The load resistance of the structures is doubled at the crown level with the crown stiffening. The Swedish design method overestimates live load moments but underestimates live load thrusts. An adjustment to the calculation of the thrusts is proposed. The Canadian design method estimates the moments relatively well but it does not cover larger spans than 8 m.