SettingsSettings for this calculationUS
The beam steel's specified minimum yield strength.
The parent section's grade, not the weld metal's. A castellated beam is cut from a rolled section and re-welded, so the flanges and web are whatever the original beam was — commonly S355 or A992 — and the splice weld is checked separately against its own strength rather than through this figure.
The overall depth of the castellated/cellular beam at the opening.
The depth AFTER castellation, which is greater than the parent section it was cut from — that increase is the entire point of the process, since it buys stiffness for no extra steel. Take it at the opening being checked rather than at the solid web post, and confirm it against the fabricator's drawing rather than assuming the nominal increase.
The height of the web opening (hexagonal or circular) at the section checked.
For a cellular beam this is the cell diameter; for a hexagonal castellation it is the full height of the opening at its widest. The net-section shear this page computes is only one of the checks an opening needs — Vierendeel bending across the tee above and below it, and buckling of the web post between two openings, both govern more often than net shear does, and neither is calculated here.
The beam web's thickness.
The parent section's web, unchanged by castellation — cutting and re-welding moves metal but does not thin it. It is the smallest dimension in the section and the one most sensitive to corrosion allowance on an exposed beam, so on anything unprotected take the thickness you expect at end of life rather than the mill figure.
Net-section shear capacity
76.8 kips
This is a basic net-section shear screening check ONLY. Vierendeel bending and web-post buckling at the opening — often the governing failure modes for castellated/cellular beams — are NOT evaluated here and require specialist software (AISC Design Guide 31, SCI P100, or FE analysis).
- Net web area at opening
- 2.56 in²
They open the calculator with your figures already in it
Castellated Beam Web Opening Net-Section Shear Calculator: 76.78 kips — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
Show calculation logicHide calculation logic
How this was calculated
Formula source(s)
- Basic net-section shear check: Vn = 0.6×Fy×Aw, where Aw = (beam depth − opening height) × web thickness. This is a starting-point screening check only — full castellated beam design also requires Vierendeel bending and web-post buckling checks (AISC Design Guide 31 / SCI P100), which are geometry-dependent, multi-step procedures with no single general formula and are NOT covered by this calculator.
Inputs used
- Steel Yield Strength Fy
- 50038.02 psi
- Beam Depth
- 20 in
- Web Opening Height
- 11.75 in
- Web Thickness
- 0.31 in
Intermediate steps
- Net web area at opening
- 2.56 in²
Confidence note: This is a basic net-section shear screening check ONLY. Vierendeel bending and web-post buckling at the opening — often the governing failure modes for castellated/cellular beams — are NOT evaluated here and require specialist software (AISC Design Guide 31, SCI P100, or FE analysis).
What this calculation does not cover
- 0.6·Fy·Aw is a nominal yield capacity with nothing applied to it. There is no resistance factor, no safety factor and no shear buckling coefficient, so setting this number against a factored load is unconservative twice over — apply φv or divide by Ωv, and check the slenderness of the web at the tee, because a deep thin web beside a large opening buckles in shear before it ever yields.
- Deflection usually decides these beams, and it is not the solid-web calculation. Shear deformation across the web posts adds materially to what a cellular or castellated beam moves under load, so a section that clears every strength check at the opening can still be too lively — and the long spans these beams get chosen for are exactly where that governs.
Add the equipment this sizes
This result is a specification — 76.8 kips — not a quantity. Put the thing it sizes into your project: how many, what you call it, and your supplier’s price.
Computed in your browser — nothing you enter is uploaded. Presented in US customary units and US trade terminology. Where a formula follows a published standard, that standard and its edition are cited beside it on this page; where none governs, the page says so. Local amendments override model codes — verify against the code in force where you build.
Sources checked 2026-09-06 · in the site-wide review of 2026-09-06 · v1.0.1
Regulatory standards & verification citations1
- Basic net-section shear check: Vn = 0.6×Fy×Aw, where Aw = (beam depth − opening height) × web thickness. This is a starting-point screening check only — full castellated beam design also requires Vierendeel bending and web-post buckling checks (AISC Design Guide 31 / SCI P100), which are geometry-dependent, multi-step procedures with no single general formula and are NOT covered by this calculator.
Cite this page
Your workspace
Most jobs need more than one number. Add the calculators you need next and they open right here, underneath this one — your figures stay on screen and nothing is lost to a page change.