As per our last article How to Structural Design a Building/House Step by Step Part-1, 2 & 3. In this article, we design slab load, slab depth, slab steel design, Slab beam design. Now in this article, we calculated a column design.
Column Design
Below Steps Column Design.
1. Column Size.
2. Column Min Steel Design.
3. Column Ring Size.
Column Size
Pu = (0.4 x fck x Ac) + (0.67 x fy x Asc)
Pu = Axial Load Kn
Ag = Gross Area of Column
fck = Strength Concrete
Ac = Ag – Asc
Asc =Â Area Steel Concrete
Minum Size of column 230 mmÂ
Column Min Steel Design
Assume 2% Steel Provided.
Asc = 0.02 Ag
Asc = 0.02 Gross Area of Column | Sp-16 ,P-229
Column Ring Size
Dia of Internal Ties | IS 456-2000, P-49
1. (1/4) x dia of a larger bar
2. 6 mm
Provide a larger to two values.
Pitch of Internal Ties | IS 456-2000, P-49
1. Least Internal Dimension
2. 16 x Dia. of Smaller Bar
3. 300 mm
Provide a smaller of three values.
Column Size Example
Load CalculationÂ
1. SlabWeight of Slab = (62.94 /2) + (180.97/2) = 121.95 kn.
2. Beam End Point weight Along lx = 13.54 kn
Weight of Beam Along Lx = (0.230 x 0.460 x 25) x 3.2 = 8.464 kn.mÂ
Along Lx Vu = (8.464 x 3.2) /2 = 13.54 kn
3. Beam End Point weight Along ly = 111.94 kn
Weight of Beam Along Ly = (0.230 x 0.460 x 25) x 9.2 = 24.334 kn.mÂ
Along Ly Vu = (24.334Â x 9.2) /2 = 111.94 kn
4. Total load Calculation = 247.435 kn
Column Size
Pu = (0.4 x fck x Ac) + (0.67 x fy x Asc)
Pu = 247.435 kn
fck = 20 N/mm2
fy = 415 N/mm2
Ac = 0.98 Ag
Pu = (0.4 x 20 x 0.98 Ag) + (0.67 x 415 x 0.02Ag )
247.435 x 103 = 13.401 Ag
Ag = √ 18496 mm2 = 136 mm ≅ 230 mm Min mumÂ
Column Min Steel Design
Asc = 0.02 Ag
Asc = 0.02 x 2302
Asc = 1058 mm2
Provide 4 Nos. 20 mm dia | SP 16, P. 229
Column Ring Size
Dia of Internal Ties| IS 456-2000, P 49
1. (1/4) x dia of a larger bar
= (1/4) x 20Â = 5mm
2. 6 mm
Provided larger 6 mm Ø lateral ties
But we, Provided 8 mm Ø lateral ties
Pitch of Internal Ties | IS 456-2000, P-49
1. Least Internal Dimension =
Least Internal Dimension = 230mm
2. 16 x Dia. of Smaller Bar
16 x 20 = 320 mm
3. 300 mm
Provide a smaller of three values.
Provide pitch = 230 mm c/c
Provided, 8 mm Ø lateral ties at 230 mm c/c
Column
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Frequently asked questions (FAQs) that could be addressed in your article on column design:
What factors determine the size of a column?
Column size is primarily determined by the axial load it needs to support (Pu), which is influenced by the strength of concrete (fck) and the yield strength of steel (fy). Additionally, the gross area of the column (Ag) and the area of steel reinforcement (Asc) play crucial roles.
How is the minimum steel reinforcement calculated for a column?
The minimum steel reinforcement (Asc) is typically specified as a percentage of the gross area of the column (Ag), commonly around 2%. This ensures that the column can withstand both compressive and tensile forces effectively.
What is the purpose of column rings in reinforced concrete structures?
Column rings, or lateral ties, are essential for confining the longitudinal reinforcement in a column. They enhance the column’s ductility and strength, particularly under seismic or lateral forces, by preventing buckling and ensuring the column remains intact during an earthquake or other lateral loads.
How do you determine the diameter and spacing of column rings?
The diameter of the column rings is typically determined based on a fraction of the diameter of the largest longitudinal reinforcement bar (commonly 1/4 of the bar diameter or as per design specifications). The spacing (pitch) of these rings is governed by standards like IS 456-2000, considering factors such as the smallest internal dimension of the column and the diameter of the longitudinal bars.
What are the design considerations for column reinforcement detailing?
Design considerations include ensuring adequate cover to reinforcement bars, proper lap lengths, development lengths at the column base and top, and ensuring the reinforcement detailing complies with code requirements for structural integrity and durability.
How does column design integrate with other structural elements like slabs and beams?
Column design is interconnected with the overall structural design of a building or house. It must account for the loads transferred from slabs and beams, ensuring that the columns can safely transfer these loads to the foundation without overstressing.
What are the consequences of inadequate column design?
Inadequate column design can lead to structural failures such as excessive deflections, cracking, or even collapse under applied loads. Proper design ensures the safety and longevity of the structure.
What are some common challenges in column design and how can they be mitigated?
Challenges may include constraints in space for reinforcement, complex loading conditions, or requirements for seismic resistance. These challenges can be addressed through meticulous analysis, proper detailing, and adherence to design codes and standards.
