Determine the lightest sections of A36 steel required for typical beams AB and AC in Figure 10-38. The dashed lines rep-resent bar joists 24 in. on center. The spandrel beams

AC carry only a small strip of floor but must support a precast concrete curtain wall that is 13-ft high. The weight of the wall is 40 lbper square foot of elevation. The floor load is 70 psf live and30 psf dead, including an allowance for all structural members.The live-load deflection of b cam AB must b less than L/360,and the total load deflection of AC must be less than L/270.