Load Capacity of Corrugated Steel Pipe with Extreme Corrosion under Shallow Cover

Across the United States, a large number of corrugated steel pipes, installed three or four decades ago, are approaching the end of their useful service life. In many cases, these aging drainage structures are having significant degrees of metal loss over their inverts due to conveyance of abrasive surface water, which can be acidic in some regions. A metal culvert under Coopermill Road near Zanesville in Muskingum County, Ohio, was selected for replacement based on its advanced level of invert metal loss. Before its replacement, invert paving was done in the half of the culvert toward its outlet end. The other half toward the inlet end was left untreated. With the concrete fully cured, each half of the culvert was instrumented with strain gauges and string potentiometers. Each half was tested under an external load of up to 267 kN (60 kip) placed over the crown. The strains and deflections were measured from the sensors, and the corresponding stresses, thrusts, and bending moments were computed. Despite the highly deteriorated conditions, the culvert structure supported a load considerably larger than the legal limit of 80 kN (18 kip). The invert-paved section of the culvert responded to the load with smaller strains, deflections, and thrusts and moments. The stresses at the interface of the steel culvert and the poured concrete treatment were not very large.