Design of a column - Reinforced Concrete with FRP Bars: Mechanics and Design - page 349

Flexural strength is

M n6 := 0 kip·ft

The strength reduction factor is

( )

ε N1

2

−

f6 f

0.65 if 1.15 − ≤ 0.65

ε

fu

( )

ε N1

2

−

φ :

=

f6 f

6

1.15 −

ε

fu

( )

ε N1

2

−

f6 f

0.75 if 1.15 − ≥ 0.75

ε

fu

φ= 0.65

6

P-M interaction diagram: Both nominal and design P-M curves are
plotted next. The black dots correspond to the pairs of ultimate bending
moment and axial force (M u , P u ) relative to the load combinations defined
in step 2. All eleven dots are enclosed within the design P-M curve and
therefore the column section is adequate to carry the design loads.

2000

1400

0.8φ 1 P n1 = 1020kip

800

200

0 80 160 240 320 400

-400

-1000

Bending Moment, kip-ft

P-M
φP-φM