Allowable Bending Stress in Compression Flange Calculator

Reduced Allowable Bending Stress Formula:

\[ Fb' = Fb \times R_{pg} \times R_e \]

Allowable Bending Stress (Fb):

MPa

Plate Girder Strength Reduction Factor (R_pg):

Hybrid Girder Factor (R_e):

Reduced Allowable Bending Stress (Fb'):

MPa

1. What is Allowable Bending Stress in Compression Flange?

Definition: This calculator determines the reduced allowable bending stress in the compression flange of plate girders when the h/t ratio exceeds certain limits.

Purpose: It helps structural engineers ensure safe design of plate girders by accounting for strength reduction due to web buckling and hybrid girder effects.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ Fb' = Fb \times R_{pg} \times R_e \]

Where:

\( Fb' \) — Reduced allowable bending stress (MPa)
\( Fb \) — Allowable bending stress (MPa)
\( R_{pg} \) — Plate girder strength reduction factor (typically 0.64 ±5%)
\( R_e \) — Hybrid girder factor (typically 0.9813 ±5%)

Explanation: The allowable bending stress is reduced by factors accounting for elastic web buckling (R_pg) and hybrid girder effects (R_e).

3. Importance of This Calculation

Details: Proper calculation ensures structural safety by accounting for reduced capacity in slender webs and hybrid girders where the web and flange have different yield strengths.

4. Using the Calculator

Tips: Enter the allowable bending stress, reduction factor (default 0.64), and hybrid factor (default 0.9813). All values must be > 0. The ±5% indicates typical variation ranges.

5. Frequently Asked Questions (FAQ)

Q1: When is this reduction necessary?
A: When the web slenderness ratio (h/t) exceeds 760/√Fb, requiring reduced bending stress in the compression flange.

Q2: What affects the plate girder reduction factor?
A: It depends on web slenderness and the ratio of web area to compression flange area.

Q3: When is the hybrid factor important?
A: Only in hybrid girders where the web yield strength is less than the flange yield strength.

Q4: How precise are the default values?
A: Defaults are typical values but may vary ±5% based on specific design conditions.

Q5: What units should be used?
A: The calculator uses MPa (Megapascals) for stress values.