1. 2.2 STRUCTURAL ELEMENT Reinforced Concrete Column
2.0 ANALYSIS AND DESIGN
2.2 STRUCTURAL ELEMENT
Reinforced Concrete Column
Rearrangement by :-
NOR AZAH BINTI AIZIZ
KOLEJ MATRIKULASI TEKNIKAL KEDAH

2. INTRODUCTION
Column is defined as a structural members subjected to compressive force.
Strut – a small compressive member in a framed structure.
Column – a larger member, such as the main support for a beam in a building.

3. INTRODUCTION
Axially loaded compressive member can fail in two principal ways:
- short fat member fail by crushing or splitting of the material.
- long thin members fail by sideways buckling.

4. Types of column i) Braced column(tiang dirembat)
– the lateral loads are resisted by wall
or some other form of bracing
ii) Unbraced column(tiang tidak dirembat)
– the lateral loads are resisted by the
bending of the column
iii) Short Column (tiang pendek)
lex/h and ley/b < 15 for a braced column
lex/h and ley/b < 10 for an unbraced column
iv) Slender(Long) Column ( tiang langsing)
ley/b >15 for a braced column
ley/b >10 for an unbraced column

5. Failure Mode
Short column (p> pcr)usually fail by crushing when the material achieved its ultimate strength.
Slender column is liable to fail by buckling
The end moment on slender column cause
it to deflect sideways exceed a critical
values until the column buckles.

6. Failure Mode Slender Column - fails by sideways buckling
- The load at which a slender column buckles, is known as its critical buckling load, P crit.
P crit. = ΩEI / L2
Where; E = Modulus of Elasticity
I = second moment of area
L = length between pins

7. Column detail

8. Reinforcement detail Longitudinal steel bar
- A minimum of 4 bars is required in a rectangular column and 6 bars in a circular column.
- The size of the bars should be not less
than 10mm
Links
- Minimum size = ¼ x size of the largest compression bar
but not less than 6mm
- Maximum spacing = 12 x size of the smallest
compression bar

9. Types of Reinforced
Concrete Column
Circular
column
Rectangular column

10. Load transfer on column for design

11. Factored Axial Load (N) for Column Design
Interior Column – 1.25
Edge/face column – 1.5
Corner column – 2
Corner column
Interior column
Edge /face column

12. Short Axially Loaded Column Design
Equation
N = 0.4 fcu Aconc+0.8 fy Asc
Where
N – Ultimate Axial load
fcu – Characteristic of concrete strength
Aconc – area of concrete cross section
fy – Characteristic of reinforcement strength
Asc – area of reinforcement cross section N

13. Example:
A column with 200 mm x 200 mm resists a factored axial load 500kN.
Calculate the area of steel required if
fy = 460 N/mm2 and fcu = 30 N/mm2
Table 1
Diameters and areas of reinforcing bars
Bar dia.(mm)
C/s area (mm2)

14. Formula for design column
N = 0.4 fcu Aconc fy Asc
500x103 = 0.4 (30) ( Asc) (460) Asc
= – 12 Asc Asc
= Asc
Asc = mm2
Asc (for each bar) = 56.18mm2/4 = 14mm2
Asc = Πj2= ΠD2/4=14mm2
D = 14 x 4 / Π
= 4.22mm
Standard required 4 number of steel reinforcement bars size 10mm minimum) . So size column = 4 T 10
4T10