> ## Documentation Index
> Fetch the complete documentation index at: https://calcs.com/docs/llms.txt
> Use this file to discover all available pages before exploring further.
# Design a Steel Composite Beam (LRFD) to AISC 360-22
> Design steel beams acting compositely with a concrete deck, through the pre-composite and composite stages, to AISC 360-22 (LRFD).
Beam reactions link to the columns and footings below, so load changes propagate downstream automatically. Design composite steel-concrete floor beams to AISC 360-22 LRFD. Covers pre-composite construction stage and final composite stage, bending, shear, stud anchor design (Chapter I), and three deflection limits in a single calculation.
## Method & scope
| Property | Detail |
| ---------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| Design standards | AISC 360-22 (LRFD) |
| Regions | United States |
| Who it's for | US structural engineers designing composite floor and roof beams to AISC LRFD, including those currently maintaining their own spreadsheets for pre-composite vs final composite stage checks. |
| Presets | Floor Joist, Floor Girder |
| What it checks | Pre-composite stage checks, Section classification (AISC 360-22 B4), Composite flexural capacity, AISC 360-22 Chapter I3, Stud anchor design, AISC 360-22 Section I8.2a, Shear capacity, AISC 360-22 Chapter G (composite stage), Composite section properties, Deflection checks, composite stage |
#### What it calculates
Beam reactions link to your column and footing calculations automatically, change a load once and everything downstream updates. For US structural engineers designing composite steel-concrete floor beams to AISC 360-22 LRFD, including those replacing manual spreadsheets for pre-composite versus final composite stage checks. Checks pre-composite bending and deflection, composite plastic moment capacity, stud anchor requirements, and three composite deflection limits.
Replaces manual spreadsheets, repeated code checks, and copied reactions with a single transparent workflow covering both construction (pre-composite) and final composite stages. Predefined ASC, Verco, and Vulcraft deck profiles make common floor systems quick to set up. Saves hours on every composite beam design.
#### Calculation method
The Steel Composite Beam (LRFD, AISC 360-22) calculator covers both the pre-composite construction stage and the final composite stage in a single template. Two independent load sets, two summary panels, and two sets of deflection criteria are maintained so you can track construction-phase adequacy and in-service performance together.
##### Pre-composite stage checks
Before the concrete slab gains strength, the steel beam alone resists construction loads. The calculator applies AISC 360-22 Chapter F and G to the bare steel section:
* **Flexural capacity**: **utilization** = Mu\_precomp / (phi × Mp\_steel) ≤ 1.0 (or reduced for FLB/WLB/LTB as applicable)
* **Shear capacity**: **utilization** = Vu\_precomp / (phi × 0.6 Fy Aw Cv1) ≤ 1.0
* **Pre-composite deflections**: instantaneous and DL+(LL or SL) deflection ratios compared to user-specified limits
A steel anchor ductility check per the prescriptive procedure is also included to confirm stud ductility requirements are met before relying on uniform shear distribution.
##### Section classification (AISC 360-22 B4)
Steel section flanges and webs are classified as compact, noncompact, or slender. For composite beams the compression flange is braced by the concrete deck in the composite stage; classification primarily affects the pre-composite flexural capacity and the post-composite negative moment region.
##### Composite flexural capacity, AISC 360-22 Chapter I3
Positive bending capacity uses the plastic stress distribution method per Chapter I3. The effective concrete flange width is computed per Section I3.1.1a. The calculator determines the governing compression force as the lesser of:
* Maximum tension force in the steel beam = As × Fy
* Maximum compression force in the slab = 0.85 f'c × Ac
For partial composite action, the compression force at the interface equals the total nominal shear strength of the stud anchors sumrV'n. The plastic neutral axis location is determined and the plastic moment resistance is calculated:
**utilization** = Mu\_comp / (phi × Mp\_composite) ≤ 1.0 where phi = 0.90
Negative bending uses the non-composite bare steel section properties (concrete in tension is ignored).
##### Stud anchor design, AISC 360-22 Section I8.2a
Individual stud anchor strength includes geometry, rib, and position reduction factors Rg and Rp. The required total shear force at the interface is determined from the governing compression force. Required stud count is computed and compared to provided studs. Detailing checks include minimum and maximum stud length, maximum longitudinal and transverse spacing per Section J3.4, and maximum diameter per Section I8.1.
##### Shear capacity, AISC 360-22 Chapter G (composite stage)
**utilization** = Vu\_comp / (phi × 0.6 Fy Aw Cv1) ≤ 1.0 with phi = 1.0 for qualifying W-shapes.
##### Composite section properties
The lower-bound elastic moment of inertia ILB is computed per AISC 360-22 Commentary I3.2 for deflection calculations. This accounts for partial composite action and provides a conservative estimate of composite stiffness under service loads.
##### Deflection checks, composite stage
Three serviceability criteria are tracked:
* **Instantaneous composite deflection**, compared to L/n or absolute limit
* **Long-term composite deflection**, includes creep under sustained loads; typically L/240
* **Simplified DL+(LL or SL) composite deflection**, combined loading for total deflection
**utilization** = delta / delta\_allow ≤ 1.0 for each criterion. A precamber recommendation is output based on dead load deflection.
##### Inputs summary
Steel section and yield strength Fy; composite action percentage; span lengths, support types, tributary width; concrete slab thickness, strength f'c, density, lightweight factor, cover; metal deck rib height, top width, bottom width, rib spacing, deck self-weight; stud diameter and ultimate strength Fu; pre-composite dead loads; composite dead and live loads; independent deflection limit criteria for pre-composite and composite stages.
##### Outputs summary
Pre-composite summary: moment and shear utilization ratios, pre-composite deflection ratios, ductility check. Composite summary: plastic moment resistance and demand, shear capacity and demand, total stud shear demand versus provided, individual stud strength, lower-bound ILB, composite deflection ratios, and precamber. All support reactions are formatted for automatic load linking to connected column and footing calculations.
## How to use it
Open it from **Run calc** in the About this calculator panel above. To start from a typical setup, choose one of the presets listed there.
Work through the input sections from top to bottom. Click any input label to see its reference explanation, clause, conditions and assumptions. See [Checks, References, Conditions and Assumptions](/docs/running-calculations/checking-results/checks-references-conditions-assumptions).
Check the utilization of each governing check in the summary, then export a PDF report. See [Views and Export](/docs/running-calculations/exporting-reports/views-and-export).
## Available presets
Each preset opens the calculator with a typical setup already entered.
| Preset | Open in Calcs.com |
| ------------------------------------- | ---------------------------------------------------------------------------------------------------------- |
| Floor Joist | [Run with preset](https://app.calcs.com/new/sheet/steelCompositeBeamLRFDAISC360-22?presetCode=floorJoist) |
| Floor Girder | [Run with preset](https://app.calcs.com/new/sheet/steelCompositeBeamLRFDAISC360-22?presetCode=floorGirder) |
## Common questions
This calculator uses LRFD per AISC 360-22. Composite flexural strength is calculated per Chapter I (plastic stress distribution method), stud anchor strength per Section I8.2a, and shear capacity per Chapter G. Pre-composite steel beam checks use Chapter F and G provisions applied to the bare steel section.
Key inputs include the steel section, yield strength Fy, composite action percentage, span lengths, tributary width, concrete slab thickness and strength (f'c), lightweight concrete factor, concrete cover, metal deck rib geometry (height, widths, spacing), stud anchor size and ultimate strength, applied pre-composite and composite loads, and deflection limit criteria for both stages.
Pre-composite stage: factored moment capacity of the bare steel beam, shear capacity, and pre-composite deflection. Composite stage: plastic moment resistance of the composite section (AISC 360-22 Chapter I3), shear capacity (Chapter G), required and provided stud anchor shear strength (Section I8.2a), stud anchor detailing checks, lower-bound moment of inertia, and three composite deflection limits. The summary also shows precamber recommendation and total stud anchor shear demand.
Yes, the composite action input allows you to specify full or partial composite action as a percentage (25% minimum per AISC 360-22). The calculator adjusts the plastic moment resistance, the lower-bound elastic moment of inertia, and the required number of stud anchors based on the specified composite ratio.
The calculator allows direct input of deck rib geometry: rib height, top rib width, bottom rib width, and rib spacing. You can enter these dimensions directly from deck manufacturer tables (ASC, Verco, Vulcraft, or any other supplier) to match your specified deck profile. The rib geometry affects the effective stud anchor strength reduction factor Rg and position factor Rp per AISC 360-22 Section I8.2a.
Yes, composite beam reactions at supports link directly to connected column and footing calculations in the same project. When span length, loads, section size, or composite ratio changes, all connected calculations update automatically, no manual re-entry.
## Next steps
Complete list of Calcs.com design calculators available for United States projects (AISC, ACI, NDS, ASCE 7, IBC, and related standards).
Design and analyze steel beams to AISC 360-22 (LRFD) with multiple supports and loads. Presets for floor and roof beams cut repetitive data entry.
Design hot-rolled steel beams to AISC 360-22 (ASD) with multiple spans and service-level loads. Checks bending, shear and three deflection limits.
Design closed-section steel beams under torsion to AISC 360-22 (ASD), checking combined bending, shear and torsion per Chapter H.
