Structural Concrete - Hassoun

408 Chapter 11 Members in Compression and Bending
8 no. 10 bars
Figure 11.30 Example 11.20: Biaxial load, PCA method: P n
= 455 K.
4. Check if M ny /M 0y > M nx /M 0x :
5.
8P n
683.8 × 8 > 12P n
or 1.463 × 10 −3 P
732.6 × 12
n > 1.365 × 10 −3 P n
Then M ny /M 0y > M nx /M 0x . Therefore, use Eq. 11.34.
8P n
683.8 × 8 + 12P n
732.6 × 12
Multiply by 1000 to simplify calculations.
1.463P n + 0.735P n = 1000
( ) 1 − 0.65
= 1
0.65
P n = 455 K P u = φP n = 295.75 K (φ = 0.65)
Note that P u is greater than the value of 274 K obtained by the Bresler reciprocal method
(Eq. 11.31) in the previous example by about 8%.
11.18 EQUATION OF FAILURE SURFACE
A general equation for the analysis and design of reinforced concrete short and tied rectangular
columns was suggested by Hsu [16]. The equation is supposed to represent the failure surface and
interaction diagrams of columns subjected to combined biaxial bending and axial load, as shown