1. Ahsanullah University of
Science & Technology
Department of Civil Engineering
Pre-stressed Concrete Lab
Imtiaz Ahmed Tilok
ID: 10.01.03.048
4th Year; 2nd Semester
Sec : A

2. Welcome To The Presentation Based On
Column Design: Biaxial

3. Column is a structural element that transmits, through
compression, the weight of the structure above to other
structural elements below. In other words, a column is a
compression member.
The biaxial bending method discussed permit
rectangular column to be designed or analyzed if
bending is present about only one of the two
principal axes of section.
Axial compression is accompanied by simultaneous
bending about both principle axes of the section.
It occurs in corner columns of building.

4. Fig: Biaxial bending plus compression

5. From this figure, we get:

6. Equivalent Eccentricity of column load
(a) Concentrically loaded column
(b) Eccentrically loaded column

7. Fig: Column subject to eccentric compression
(a)loaded column
(b)Strain distribution at section a-a
(c)Stress and forces at nominal strength

8. Nominal load,
Nominal moment,

10. Balanced Failure, eb

11. Fig: Interaction diagram for nominal column strength in
combined bending and axial load
Interaction Curve

12. Interaction diagram for compression plus biaxial bending
(a) Uniaxial bending about y axis
(b)Uniaxial bending about X axis
(c)Biaxial bending about diagonal axis
(d)Interaction surface

13. Methods :
There are three types of method.
1.Load Contour Method
2.Reciprocal Load Method
3.Computer Analysis For Biaxial Bending Of
Columns.

14. Load Contour Method
Where
Where,

15. Reciprocal Load Method
Fig: Interaction surface for the reciprocal load method

16. • The 12×20 in column shown in fig is reinforced with
eight no.9 bars arranged around the column perimeter,
providing an area Ast=8 in². A factored load Pu of
255 kips is to be applied with eccentricities
=3in, =6in.
material strengths are ƒ’c = 4 ksi and ƒʏ= 60 ksi.
Check adequacy by trial design using
a. Reciprocal load method
b. Load contour method.
EXAMPLE: DESIGN OF COLUMN
FOR BIAXIAL BENDING

17. Problem Figure:

23. THANK YOU