Question

a. An empty school bus weighs ~25,000 lbs. Loading on 60 children times 80 lbs. per child adds another 4,800 lbs. The bus has four wheels, each 10 inches wide and with a contact length (the length of tire touching the road when fully inflated) of 4 inches. First calculate the total contact area of the bus, and then determine how much pressure is the bus exerting on the pavement under the wheels.

b. This pressure compresses the pavement, which opposes this force through its compressive strength. Typical asphalt pavement at room temperature has a compressive strength of 600 pounds per square inch (psi). How heavy would the bus have to be to cause damage to the pavement?

c. Now suppose the bus gets a flat tire. This decreases the contact area of one of the wheels down to just the narrow rim of the wheel, or 0.5 in2. What is the new pressure exerted by this wheel? (Assume that 1/4 of the bus supported by this wheel – the other wheels are as in part a.) Is this enough to damage the pavement?

Please answer all 3 questions.?

Answer 1

Here contact area is assumed to be elliptical in nature and contact pressure is obtained by dividing the wheel load by contact area. See the solution.