In: Civil Engineering
A simply supported beam is required to carry a moment of 50 kip-ft across a 25' span. Assuming that 4 and 8 ksi concrete are available, with a cost difference of 30 percent. Use 60 ksi steel. Beam width is fixed at 12 inches. You can Vary h.
a)design the beam using 2 different concretes - dont forget beta is different.
Please note that minimum depth has been considered to limit deflection and hence the choice of concrete does not affect much in the design of beam sections and reinforcements.