Width of Footing given Ultimate Bearing Capacity Calculator

Width of Footing Formula:

\[ B = \frac{q_{fc} - (C \times N_c + \gamma \times D_{footing} \times N_q)}{0.5 \times \gamma \times N_\gamma} \]

Ultimate Bearing Capacity (q_fc):

Cohesion in Soil (C):

Bearing Capacity Factor (N_c):

Unit Weight of Soil (γ):

N/m³

Depth of Footing (D_footing):

Bearing Capacity Factor (N_q):

Bearing Capacity Factor (N_γ):

Width of Footing (B): m

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

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

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:

\[ B = \frac{q_{fc} - (C \times N_c + \gamma \times D_{footing} \times N_q)}{0.5 \times \gamma \times N_\gamma} \]

Where:

\( B \) — Width of footing (meters)
\( q_{fc} \) — Ultimate bearing capacity in soil (Pascals)
\( C \) — Cohesion in soil (Pascals)
\( N_c \) — Bearing capacity factor dependent on cohesion (±5%)
\( \gamma \) — Unit weight of soil (N/m³)
\( D_{footing} \) — Depth of footing in soil (meters)
\( N_q \) — Bearing capacity factor dependent on surcharge (±5%)
\( N_\gamma \) — Bearing capacity factor dependent on unit weight (±5%)

Explanation: The formula calculates the minimum footing width required to distribute the load within the soil's bearing capacity.

3. Importance of Footing Width Calculation

Details: Proper footing width ensures structural stability, prevents excessive settlement, and maintains safety factors in foundation design.

4. Using the Calculator

Tips: Enter all required parameters. Bearing capacity factors typically have ±5% variability. Ensure all values are positive.

5. Frequently Asked Questions (FAQ)

Q1: What are typical values for bearing capacity factors?
A: Common values are Nc=9, Nq=2.01, Nγ=1.6, but these vary with soil type and angle of internal friction.

Q2: How is ultimate bearing capacity determined?
A: Through soil testing or empirical relationships based on soil properties.

Q3: Why is cohesion sometimes zero?
A: Granular soils like sand typically have zero cohesion.

Q4: How does footing depth affect the calculation?
A: Deeper footings benefit from surcharge effect, potentially reducing required width.

Q5: What safety factors should be considered?
A: Typical safety factors range from 2.5-3.0 for bearing capacity calculations.