Deep beams calculator

Beam Size Calculator — IS 13920 Guidance

Preliminary geometry guide: D = L/12 to L/10, b ≈ D/1.5, and b ≥ minimum width. This calculator provides preliminary geometry and reinforcement visualization only.

Clear Span L (m)

Preferred depth selection Auto (mid of L/12 & L/10) L/12 (shallower) L/10 (deeper) Custom depth (mm)

Clear cover to reinforcement (mm) Input value is used in the approximate effective-depth calculation.

Stirrup / link diameter (mm)

Main longitudinal bar diameter (mm)

Minimum beam width allowed (mm) This is a user-selected minimum for this preliminary tool.

Width selection rule Width = D / 1.5 Fixed width (mm)

Display & actions

Beam Cross-section (dynamic)

Illustrative section only. Reinforcement quantity and spacing are not design outputs.

Results

Calculating…

Engineer notes

• This tool provides preliminary geometry and visualization; it does not replace a complete structural design.
• Approximate effective depth is calculated as d = D − (cover + stirrup dia + 0.5 × main bar dia).
• Full bending, shear, serviceability, anchorage, development length and ductile-detailing checks must be carried out separately.
• This visualization assumes a rectangular beam and does not design a T-beam flange.

Detailed Solved Example

The following example uses the same calculation logic as the interactive calculator. It is deliberately separated from the calculator so that the JavaScript cannot accidentally overwrite or depend on example-page elements.

1. Given data

Clear span, L = 6.00 m
Depth rule = Auto (mid of L/12 and L/10)
Width rule = D/1.5
Minimum width = 200 mm
Clear cover = 25 mm
Stirrup diameter = 8 mm
Main bar diameter = 16 mm

2. Step 1 — Convert span to millimetres

L = 6.00 × 1000 = 6000 mm

3. Step 2 — Preliminary depth range

D_L/12 = 6000 / 12 = 500 mm

D_L/10 = 6000 / 10 = 600 mm

Preliminary depth range = 500–600 mm

4. Step 3 — Select overall depth

D = (500 + 600) / 2 = 550 mm

Selected overall depth D = 550 mm

5. Step 4 — Calculate width

b = D / 1.5 = 550 / 1.5 = 366.67 mm

Rounded b = 367 mm

Since 367 mm > 200 mm minimum, no minimum-width correction is required.

Preliminary calculated section = 367 × 550 mm

6. Step 5 — Approximate effective depth

d = D − (cover + stirrup dia + 0.5 × main bar dia)

d = 550 − (25 + 8 + 0.5 × 16)

d = 550 − (25 + 8 + 8) = 509 mm

Approximate effective depth d = 509 mm

7. Step 6 — Rough deep-beam flag

L/8 = 6000 / 8 = 750 mm

D = 550 mm < 750 mm

Tool flag: Typical flexural behaviour expected (still check design).

8. Summary

Parameter	Result
Clear span L	6000 mm
Depth from L/12	500 mm
Depth from L/10	600 mm
Selected overall depth D	550 mm
Calculated width D/1.5	366.67 mm
Rounded width b	367 mm
Clear cover	25 mm
Stirrup diameter	8 mm
Main bar diameter used for d	16 mm
Approximate effective depth d	509 mm

9. Important engineering limitation

The calculated 367 × 550 mm section is a preliminary geometry result. It is not a final reinforcement design. Actual beam design requires loading, support conditions, material grades, load combinations, bending, shear, serviceability and applicable ductile-detailing checks.

10. Recommended engineering workflow

1. Select preliminary beam dimensions.
2. Determine dead and imposed loads.
3. Establish support conditions and design load combinations.
4. Calculate design bending moments and shear forces.
5. Design longitudinal reinforcement.
6. Check minimum/maximum reinforcement.
7. Design shear reinforcement.
8. Apply applicable ductile-detailing provisions.
9. Check serviceability and constructability.
10. Prepare the final reinforcement drawing only after all checks pass.

Yogendra Gopal Borse

Civil Engineer | Assistant Engineer Grade-I, Maharashtra PWD

B.Tech (Civil) from VJTI Mumbai. Experienced in bridge design, road works, estimation, project monitoring and digital engineering tools. Creator of YogiPWD – practical technical resources for civil engineers.

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