Width of Footing given Safe Bearing Capacity Calculator

Width of Footing Formula:

\[ B = \frac{(q_{sa} \times fs - fs \times \sigma_s) - (C \times N_c + \sigma_s \times (N_q - 1))}{0.5 \times \gamma \times N_\gamma} \]

Safe Bearing Capacity (kPa):

Factor of Safety:

Effective Surcharge (kPa):

Cohesion in Soil (kPa):

Bearing Capacity Factor (Cohesion):

Bearing Capacity Factor (Surcharge):

Unit Weight of Soil (kN/m³):

Bearing Capacity Factor (Unit Weight):

Width of Footing (m):

1. What is Width of Footing given Safe Bearing Capacity?

Definition: This calculator determines the required width of a footing based on the soil's safe bearing capacity and other geotechnical parameters.

Purpose: It helps civil engineers and construction professionals design appropriate foundation dimensions to ensure structural stability.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ B = \frac{(q_{sa} \times fs - fs \times \sigma_s) - (C \times N_c + \sigma_s \times (N_q - 1))}{0.5 \times \gamma \times N_\gamma} \]

Where:

\( B \) — Width of Footing (meters)
\( q_{sa} \) — Safe Bearing Capacity (kPa)
\( fs \) — Factor of Safety
\( \sigma_s \) — Effective Surcharge (kPa)
\( C \) — Cohesion in Soil (kPa)
\( N_c \) — Bearing Capacity Factor (Cohesion)
\( N_q \) — Bearing Capacity Factor (Surcharge)
\( \gamma \) — Unit Weight of Soil (kN/m³)
\( N_\gamma \) — Bearing Capacity Factor (Unit Weight)

Explanation: The formula accounts for soil properties, surcharge loads, and safety factors to determine the minimum footing width needed to safely distribute structural loads.

3. Importance of Footing Width Calculation

Details: Proper footing width ensures the foundation can support structural loads without exceeding the soil's bearing capacity, preventing settlement or failure.

4. Using the Calculator

Tips: Enter all required parameters. Default values are provided for common soil conditions. All values must be positive numbers. Results have ±5% accuracy.

5. Frequently Asked Questions (FAQ)

Q1: What is safe bearing capacity?
A: The maximum pressure the soil can withstand without risk of shear failure, typically determined through geotechnical testing.

Q2: How is factor of safety determined?
A: It depends on soil conditions and importance of structure. Common values range from 2.5 to 3.5 for foundations.

Q3: What is effective surcharge?
A: Additional vertical pressure from adjacent structures, backfill, or other surface loads near the footing.

Q4: How do I get bearing capacity factors?
A: These are determined from soil properties and foundation geometry, often using Terzaghi's or Meyerhof's theories.

Q5: Why does cohesion matter?
A: Cohesive soils (like clay) can support more load than granular soils due to their internal bonding strength.