Q#3. A) An AASHTO prestressed simply supported I beam has a span of 34ftand is 36in. deep. Its cross section is shown. it is subjected to a live load intensity W =3600plf. Determine the required 1/2" dia, stress relieved, seven wire strand, to resist the applied gravity load and self-weight of the beam assuming the tendon eccentricity at midspan e.= 13.12 in. Maximum permissible stress are as follows f = 6000 psi (41.4 MPa) fpu=270,000 psi (1862 MPa) Spe 145,000 psi (1000 MPa) The section properties, given these stresses, are Q#4: A 369 in. I = 50,979 in.* Ic A Cb 15.83 in. Sb = 3220 in. St = 2527 in. WD = 384 plf WL 3600 plf 2 = Section Properties Untopped Ac = = = 1185 in.2 = 109,621 in.4 25.65 in. 8.35 in. 4274 in. 13,128 in. 1234 plf 82 psf 2.45 in. 138 in. Solution#3 (to be typed here by the student 2'-10" 4" C Sb St WD V/S = Solve it by all 3 methods 4 3'-0" A simply supported pretensioned pretopped double T-beam for a floor has a span of 70 ft (21.3 m) and the geometrical dimensions shown in Figure P1.3. It is subjected to a gravity live-load intensity W = 480 plf (7 kN/m), and the prestressing tendon has an eccentricity at midspan of e. = 19.96 in. (494 mm). Compute the concrete extreme fiber stresses in this beam at transfer and at service load, and verify whether they are within the permissible limits. Assume that all permissible stresses and materials used are the same as in example 1.1. The section properties are: -14-1134 7'-6" 2'-6" 6" -3-87/8" 1'-3" 6" 6" + Solution#4 (to be typed here by the student) 1'-0" 6" 1'-6" -3'-87/8-