FIGURE 37. Magnel diagram.- For the case where e is restricted to 18 in (457.2 mm), minimize
FJ by determining the ordinate of point G on line b
Thus, in Fig. 37, l/F{ = (10 + 18)712.91; F 1 = 461 kips (2050.5 kN).
The Magnel diagram may be applied to a beam having deflected tendons by substitut-
ing for Mw in Eqs. 51a and 57c the beam-weight moment at the deflection point.
CAMBER OF A BEAM AT TRANSFERThe following pertain to a simply supported prismatic beam: L = 36 ft (11.0 m); / =
40,000 in^4 (166.49 dm^4 );/,;. = 4000 lb/in^2 (27,580.0 kPa); ww = 340 Ib/lin ft (4961.9
N/m); Ft = 430 kips (1912.6 kN); e = 8.8 in (223.5 mm) at midspan. Calculate the camber
of the member at transfer under each of these conditions: (a) the tendons are straight
across the entire span; (b) the tendons are deflected at the third points, and the eccentrici-
ty at the supports is zero; (c) the tendons are curved parabolically, and the eccentricity at
the supports is zero.
Calculation Procedure:- Evaluate E 0 at transfer, using the ACI Code
Review the moment-area method of calculating beam deflections, which is summarized
earlier. Consider an upward displacement (camber) as positive, and let the symbols Ap,
Aw, and A 1 -, defined earlier, refer to the camber at midspan.