Type D Soil

Designing columns for buildings, whether single-storey or multi-storey (up to 10 storeys), involves a comprehensive understanding of load distribution, material strengths, and soil conditions. Below are some thumb rules for column design and steel calculation for buildings up to 10 storeys, considering Type D soil (which generally indicates stiff soil or soft rock with moderate strength):

Thumb Rules for Column Design

1. Column Size:
   • Single Storey: Minimum column size is 9” x 9” (230 mm x 230 mm) using M20 grade concrete. However, this can vary based on the load and structural requirements.
   • 2 to 3 Storeys: Increase column size to 12” x 9” (300 mm x 230 mm) or 12” x 12” (300 mm x 300 mm).
   • 4 to 5 Storeys: Minimum column size is 15” x 12” (375 mm x 300 mm) or 15” x 15” (375 mm x 375 mm).
   • 6 to 10 Storeys: Column size can be 18” x 18” (450 mm x 450 mm) or larger, depending on load calculations.
2. Steel Reinforcement:
   • Single Storey: Use 4 bars of 12 mm diameter (Fe500 steel).
   • 2 to 3 Storeys: Use 6 bars of 12 mm diameter or 4 bars of 16 mm diameter.
   • 4 to 5 Storeys: Use 8 bars of 16 mm diameter.
   • 6 to 10 Storeys: Use 10 to 12 bars of 20 mm or 25 mm diameter.
3. Steel Calculation (Thumb Rule):
   • For Residential Buildings: 1% to 2% of the cross-sectional area of the column.
   • For Commercial Buildings: 2% to 3% of the cross-sectional area of the column.

Example Calculation:

For a 5-storey building with a 15” x 15” (375 mm x 375 mm) column:

• Area of Column: 375 mm x 375 mm = 140625 mm²
• Steel Requirement (2% of column area for residential building):
  • Steel area = 0.02 x 140625 mm² = 2812.5 mm²
  • Using 16 mm diameter bars (area = 201 mm² per bar):
    • Number of bars required = 2812.5 mm² / 201 mm² = 14 bars (rounded up for practical design)

Important Considerations:

1. Load Calculations:
   • Dead Load: Weight of the structure itself.
   • Live Load: Occupancy loads.
   • Wind Load: Depending on the height of the building.
   • Seismic Load: Based on the seismic zone.
2. Soil Bearing Capacity:
   • Type D soil typically has a bearing capacity around 100-200 kN/m². Ensure that the foundation design accommodates this to prevent excessive settlement.
3. Concrete Grade:
   • M20 or higher grade for residential buildings.
   • M25 or higher for commercial buildings.
4. Safety Factors:
   • Include appropriate safety factors as per local building codes and standards.
5. Building Codes:
   • Follow the local building codes and standards (such as ACI318 and IS 456 etc.) for detailed and accurate design.

Final Note:

These thumb rules provide a quick reference, but detailed structural analysis and design should be performed by a qualified structural engineer using relevant design codes and standards, especially considering the specifics of load distribution, soil properties, and building use.