SHEAR CAPACITY OF U-BOLT CONNECTIONS IN TRANSIT BUSES

Laboratory tests were conducted to assess the shear capacity of U-bolt connections used in most transit buses to attach the bus frame and body to the bus chassis. These tests involved the connections in two medium-duty transit buses designed and built in Michigan for the Michigan Department of Transportation. For each test specimen, the shear forces applied and the relative displacements of the components representing the bus frame and chassis were recorded. The results indicated no correlation between the initial U-bolt torque and the shear capacity of the connections, whereas very substantial increases in the rate of load application resulted in slight to moderate decreases in the shear capacity. Increases in the number of U-bolts per specimen from two to three caused slight decreases in average U-bolt shear strength, and substantial increases in the chassis depth caused substantial increases in the U-bolt shear capacity.