Width of Footing given Bearing Capacity for Square Footing Calculator

Footing Width Formula:

\[ B = \left(\frac{q_f - \sigma_s}{C \times N_c} - 1\right) \times \frac{L}{0.3} \]

Ultimate Bearing Capacity:

kPa

Effective Surcharge:

kPa

Cohesion in Soil:

kPa

Bearing Capacity Factor:

Length of Footing:

Tolerance:

Calculated Width (m):

1. What is Footing Width Calculation?

Definition: This calculator determines the required width of a square footing based on soil bearing capacity, cohesion, and other geotechnical factors.

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

2. How Does the Calculator Work?

The calculator uses the formula:

\[ B = \left(\frac{q_f - \sigma_s}{C \times N_c} - 1\right) \times \frac{L}{0.3} \]

Where:

\( B \) — Width of footing (meters)
\( q_f \) — Ultimate bearing capacity (kPa)
\( \sigma_s \) — Effective surcharge (kPa)
\( C \) — Cohesion in soil (kPa)
\( N_c \) — Bearing capacity factor (typically 9 for square footings)
\( L \) — Length of footing (meters)

Explanation: The formula calculates the minimum footing width needed to distribute structural loads safely to the soil.

3. Importance of Footing Width Calculation

Details: Proper footing width ensures structural stability, prevents settlement, and maintains safety factors against bearing capacity failure.

4. Using the Calculator

Tips: Enter all required parameters including soil properties and structural loads. The tolerance field (default ±5%) provides a safe design range.

5. Frequently Asked Questions (FAQ)

Q1: What is the typical bearing capacity factor (Nc)?
A: For square footings, Nc is typically 9. This may vary for different foundation shapes and soil conditions.

Q2: How do I determine soil cohesion?
A: Cohesion is determined through geotechnical testing like triaxial or unconfined compression tests.

Q3: What's the purpose of the tolerance field?
A: The tolerance provides a safety margin to account for material variability and construction tolerances.

Q4: Can this be used for rectangular footings?
A: This formula is specifically for square footings. Different factors apply for rectangular or circular footings.

Q5: How does surcharge affect footing width?
A: Higher surcharge reduces the required footing width as it contributes to bearing capacity.