Strengthening of Columns for Confinement - Strengthening Design of Reinforced Concrete with FRP - page 212

20 in

0.003

e´

0.00254

e

0.001

22 in

24 in 20 in

-0.000533

-0.00207

FIGURE 7.30 Determination of Point C on the unconfined interaction diagram.

h

2112.62 e +− = d 29,947.11

2

e = 4.175"

2112.62 M

M

= × 4.175 = 8820.91 k-in.735.1k-ft =

nB

φ=× 0.65 735.1 = 477.8k-ft nB

3. Point C: Compression + bending when the balanced behavior is observed
(Figure 7.30)

0.003 0.00507

22

= c = 13.02"

c

a = 0.75 × = c 9.765"

P = 0.85 × ×× +×+ 6.0209.765 3.81 60 2.54 × 29,000 × 0.001 n C

− 2.54 × 29,000 × 0.000533

1259.03 k
818.4k

=
φ=

P n C

9.765
2

Pe ×= ××× 0.85 6.0209.765 × 22 − + ×× 3.81 60 20

n c

2
3

+ 2.54 × 29,000 × 0.001 × 20

20
3

− 2.54 × 29,000 × 0.000533 ×

=
×+−=

22,341.94

( )

1259.03 e 12 2 2, 341.94

e = 7.745"

M = 1259.03 × 7.745 = 9751.64 k-in. 12.64 k-ft =

nC

M 528.21 k-ft

φ=

nC