Steel Deck Calculator

Steel roof and floor deck design checks per SDI standards. Bending, shear, and deflection for composite and non-composite metal deck configurations. Educational use only.

This page documents the scope, inputs, outputs, and computational approach of the Steel Deck Calculator on steelcalculator.app. The interactive calculator runs in your browser; this documentation ensures the page is useful even without JavaScript.

What this tool is for

Checking bending, shear, and deflection capacity of metal deck profiles per SDI (Steel Deck Institute) standards.
Comparing deck gages and profiles for given span and load conditions.
Understanding the difference between composite and non-composite metal deck design.

What this tool is not for

It does not design the composite concrete slab or the shear stud anchorage to the supporting beam.
It does not check diaphragm shear capacity of the deck for lateral load resistance.
It does not handle special conditions like cantilevers, concentrated loads, or fire-rated assemblies.

Key concepts this page covers

SDI deck profile designations (1.5B, 2N, 3N, etc.)
section properties of corrugated deck (effective width method)
single-span, double-span, and triple-span deck conditions
composite deck with concrete fill vs. form deck

Inputs and outputs

Typical inputs: deck profile type, gage (thickness), span length, number of spans, concrete fill depth (for composite), applied dead and live loads, and deflection criteria.

Typical outputs: allowable uniform load, moment capacity, shear capacity, deflection under service load, and the controlling limit state (bending, shear, deflection, or web crippling).

Computation approach

The calculator uses the effective section properties for the specified deck profile, computed using AISI S100 effective width provisions for the compression elements. Positive and negative moment capacities are checked for multi-span conditions using appropriate moment coefficients. Shear capacity includes web shear and web crippling at supports. Deflection is computed using standard beam formulas for the appropriate span condition.

Frequently Asked Questions

What is the difference between composite and non-composite metal deck? Composite metal deck has embossments or other shear transfer features that bond the deck to the concrete fill, creating a reinforced composite slab where the deck acts as the bottom reinforcement. Non-composite (form) deck serves only as formwork for the concrete during construction; after the concrete cures, the slab strength is determined by conventional reinforced concrete design. Composite deck is more economical for floor systems because it eliminates the need for bottom reinforcement bars.

How does the number of spans affect deck capacity? Multi-span (continuous) deck has higher load capacity than single-span deck because the negative moment at interior supports partially offsets the positive moment at midspan, resulting in lower maximum moment for the same load. A three-span condition typically carries about 20% more load than a single span of the same length. However, the negative moment at supports may govern for certain load patterns, so the design must check all critical sections.

What deflection limits apply to metal deck? SDI and IBC typically limit the deflection of metal deck under construction loads (before concrete is placed) to L/180 or 3/4 inch, whichever is less. For composite floor deck under service loads, the concrete slab deflection limit is typically L/360 for live load. For roof deck, the deflection limit is typically L/240 for total load. These limits prevent ponding on roofs and ensure adequate flatness for floor finishes.

Disclaimer (educational use only)

This page is provided for general technical information and educational use only. It does not constitute professional engineering advice, a design service, or a substitute for an independent review by a qualified structural engineer. Any calculations, outputs, examples, and workflows discussed here are simplified descriptions intended to support understanding and preliminary estimation.

All real-world structural design depends on project-specific factors (loads, combinations, stability, detailing, fabrication, erection, tolerances, site conditions, and the governing standard and project specification). You are responsible for verifying inputs, validating results with an independent method, checking constructability and code compliance, and obtaining professional sign-off where required.

The site operator provides the content "as is" and "as available" without warranties of any kind. To the maximum extent permitted by law, the operator disclaims liability for any loss or damage arising from the use of, or reliance on, this page or any linked tools.