(275,800.0 kPa), and set s = 12 in (304.8 mm). Then Av = 12(20,200 - 0.85 x
17,000)/[0.85(11.09)(40,000)] = 0.184 in^2 /ft (3.8949 cm^2 /m). This is the area required at
the ends.
Calculate the minimum web-reinforcement area by applying
-A ^L S
^' 80 Jy (b'df* ^^or Av = (1.089/80)(248,000/40,000)12/(12.74 x 11.09)°^5 = 0.085 in^2 /ft (1.7993 cm^2 /m).
- Calculate the camber under full dead load
From the previous procedure, E 0 = (^1 / 3 )(3.644)(10)^6 - 1.215 x 106 lb/in^2 (8.377 x 106
kPa); EJ= 1.215(10)^6 (7240) = 8.8 x io^9 lb-in^2 (25.25 x io^6 N-m^2 ); AADL = -5(401)
(40)^4 (1728)/[384(8.8)(10)^9 ] = -2.62 in (-66.548 mm). By Eq. 58, A^ = 0.85(181,400)
(6.07)(40)^2 (144)/[8(8.8)(10)^9 ] = 3.06 in (77.724 mm); ); A = 3.06 - 2.62 = 0.44 in (11.176
mm).
DESIGN OFA POSTTENSIONED GIRDER
The girder in Fig. 42 has been selected for use on a 90-ft (27.4-m) simple span to carry the
following superimposed loads: dead load, 1160 Ib/lin ft (16,928.9 N/m), live load, 1000
Ib/lin ft (14,593.9 N/m). The girder will be posttensioned with Freyssinet cables. The con-
crete strengths are/; = 5000 lb/in^2 (34,475 kPa) and/c; = 4000 lb/in^2 (27,580 kPa). The
allowable stresses are: initial, + 2400 and-190 lb/in^2 (+ 16,548 and-1310.1 kPa); final,
+2250 and -425 lb/in^2 (+ 15,513.8 and -2930.4 kPa). Complete the design of this mem-
ber, and calculate the camber at transfer.
FIGURE 42