F. K. Kong MA, MSc, PhD, CEng, FICE, FIStructE, R. H. Evans CBE, DSc, D ès Sc, DTech, PhD, CEng, FICE, FIMechE, FIStructE (auth.)-Reinforced and Prestressed Concrete-Springer US (1987)

BS 8110 design procedure 269
y
IT ·l~x
h[
h' -t· -eM:
. I .
Fig. 7.3-3
-+···+y
2.3% of 300 mm by 500 mm = 3450 mm2
Use 6 size 32 bars ( 4825 mm2)
(b) Nand My. (In this case, b = 500 mm and h = 300 mm.)
N (2300)(10 3 ) 2
bh = (500)(300) = 15.33 N/mm
My (120)(10 6 ) 2
bh2 = (500)(3002) = 2.67 N/mm
From Fig. 7.3-1,
Asc = 1.3%
1.3% of 300 mm by 500 mm = 1950 mm2
Use 4 size 25 bars (1963 mm2)
Example 7.3-2 (Biaxial bending)
Design the longitudinal reinforcement for the 500 by 300 mm column
section in Example 7.3-1 if N = 2300 kN, Mx = 300 kNm and My= 120
kNm. Given: feu = 40 N/mm2 and /y = 460 N/mm2.
SOLUTION
Step I Calculate the enhanced moment (M~ or M~)
Assuming, say, 50 mm cover to centres of bars, then (see Fig. 7.3-3)