Design a series of closely spaced parallel box beams that will support an asphalt road surface over a 10 foot wide, 40 foot long span. The hollow box beams are made of concurred and imbedded No. 8 steel rods (1 inch dia.). Maximum beam height is 30 inches. Minimum concrete thickness is 2 inches and in regions where steel rods are used, concrete cover over the steel rods must be at least 2 inches thick (there must be at least 2 inches of concrete covering the steel in all directions). The external bridge loading is 500lbs per square foot. Assume the asphalt surface is free to slide (not attached) over the box beams. Other assumptions you can make:
Concrete compression strength 4000 psi
Concrete density 140 lbs per cubic foot
Steel yield strength 40000 psi
The weight of the bridge itself must be considered.
Use the "Civil Engineering" Method to calculate all properties of the beams. Specify the number of box beams, their dimensions (h, w, t1, t2, t3, t4), and the location and number of steel bars in each box beam. Support your design with appropriate calculations.
Note: Closely spaced means next to each other, otherwise the asphalt would drip down between the beams.