System capacity of vintage reinforced concrete moment frame culverts
University of Delaware
The Delaware Department of Transportation (DelDOT) currently has around 300 reinforced concrete moment frame culverts with spans ranging from 6 to 20 ft (1829 and 6096 mm) in its inventory. A problem that DelDOT's bridge engineers have is that these culverts often do not pass current LRFR load rating procedures and as a result many of them have to be posted to prohibit larger trucks from passing. However, none of these structures have shown significant wear or deterioration or experienced failure. A total of five full-scale culvert specimens were constructed and tested in the University of Delaware Structures Laboratory. The dimensions of the first three specimens were 10 ft. x 2 ft. (3040 mm x 610 mm), Specimen 4 was 10 ft. x 11 ft 4in. (3048 mm x 3454 mm), and Specimen 5 was 16 ft. x 2 ft. (4877 mm x 610 mm). The loading configuration varied between a single tire patch at mid-span and AASHTO tandem axle loading. The loading protocol consisted of loading the specimen to a specific load level and holding the load until the displacements and strains held constant. Subsequently, the specimen was unloaded to a small value before it was reloaded to a higher load. This was repeated until the specimens failed. The ultimate failure modes for Specimens 1, 2, 3, and 5 was shear which occurred after excessive deflections were present. In all cases, the regions with the maximum positive and negative bending moments were able to develop plastic hinges, i.e. yield moments were reached to form a mechanism. Specimen 4 failed in punching shear rather than flexural-mode due to the effective transverse load distribution.