Here we will learn some basic knowledge about column design rule as per ACI CODE
STRENGTH OF CONCRETE
Ø Compressive strength of concrete, (𝑓𝑐′) shall not be less than 17 MPa.
Ø Modulus of elasticity, 𝐸𝑐, for concrete shall be permitted to be taken as 〖Wc〗^1.50.043√𝑓𝑐′ (in MPa) for values of W𝑐 between 1440 and 2560 kg/m3.
Ø For normal weight concrete, 𝐸𝑐 shall be permitted to be taken as 4700√𝑓𝑐′ (in MPa).
DESIGN STRENGTH OF REINFORCEMENT
Ø Design strength of reinforcement represented by the values of 𝑓𝑦 used in design calculations shall not exceed 550 MPa .
Ø for transverse reinforcement 𝑓𝑦 may exceed 420 MPa .
Ø Modulus of elasticity, 𝐸𝑠, for reinforcement shall be permitted to be taken as 200,000 MPa.
STRENGTH REDUCTION FACTOR 𝜙
For compression-controlled sections,
Ø Members with spiral reinforcement conforming à 0.75
Ø Other reinforced members à 0.65
Column Design Rule
LIMITS OF REINFORCEMENT FOR COMPRESSION MEMBERS
Ø The area of longitudinal reinforcement, 𝐴𝑠𝑡, shall be not less than 0.01𝐴𝑔 or more than 0.06𝐴𝑔.
Ø Minimum number of longitudinal bars in compression members shall be ,
- 4 for bars within rectangular or circular ties
- 3 for bars within triangular ties
- 6 for bars enclosed by spirals conforming
Ø MOMENTS OF INERTIA, 𝐼= 0.70𝐼𝑔
ØFor compression members, the clear distance between longitudinal bars shall be not less than
- 1.5 bar diameters
- 40 mm (1.5in)
- 1.33 times of maximum nominal size of coarse aggregate.
Ø Minimum cross-sectional dimension for a Column: is 9″x 12″ (225 MM x 300 MM) which is the minimum recommended size.
Ø Required Reinforcement for a Column: minimum 1% and maximum 8% of Cross sectional area of column.
