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Instantly create a new Steel Beam with Torsion calculation by clicking here:Create Steel Beam with Torsion Calculator(This link automatically opens a new project and sheet in Calcs.com.)
Follow along in this video or the below article to see an overview of the key assumptions, inputs and outputs for steel HSS with torsion:
The calculator shares most assumptions with the standard Steel Beam calculator, with a few torsion-specific notes:
  • Warping torsion is not considered; only closed-section torsional checks are performed.
  • Members are assumed to be straight and prismatic (no tapering).
  • Axial loads due to twist are assumed negligible.
    • This is a particularly important point for inclined beams, in which axial load is by definition non-zero; it is left to the engineer to verify that the axial load is, in fact, negligible.
1

Inputting Key Properties

At the top of the calculator, you’ll choose your steel section:
  1. Open the Member Selector.
  2. Select the desired HSS section (closed sections only are currently supported for torsion).
  3. Adjust material and member properties as needed:
    • Yield strength (Fy)
    • Beam span length
    • Bracing conditions
You can also modify the support conditions using the support table provided.Screenshot 2025-12-08 at 2.04.33 PM.png
2

Applying Torsional Load Input

The first load shown is the Required Torsional Load (T_req):
  • This value represents the factored torsional moment applied to the beam.
  • This load represents the twist-inducing moment acting on the member.
This value is the maximum torsion in the beam using ASD loads. Note that it needs to be factored when inputted as the torsional load (Ta) is equivalent to the required torsional load (Tr).
3

Applying Additional Loads

Similar to the regular Steel Beam calculator, you may add:
  • Distributed loads
  • Line loads
  • Point loads
These are entered using the corresponding tables and can be customized according to your project requirements.

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Reviewing the Calculations

This calculator will compute the flexural capacity based on AISC 36-16 Chapter F. Similar to the steel beam calculator, governing lateral torsional buckling checks are completed. Calcs.com checks for the moment modification factor using the quarter-moment method, which is later used to determine the LTB moment resistance. This calculator also does a simple shear capacity check. For the closed section torsion checks, you can scroll to the bottom of the calculator and open the below dropdown. Screenshot 2025-12-08 at 2.14.42 PM.png The critical local buckling stress is computed from AISC 360-16 Chapter H and takes into account the HSS torsional constant, as well as the critical torsion stress.

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Combined Loading Check

If your torsional demand exceeds 20% of the allowable torsional strength, the calculator automatically performs a combined torsion + shear + axial interaction check. For example, if the torsional demand is increased to reflect higher loading:
  • The calculator evaluates the interaction equation defined by AISC.
  • A combined utilization result (e.g., 0.54 < 1.0) will appear, confirming compliance.
This check ensures your design remains valid under realistic combined effects. When the required torsional strength, Ta, is less than or equal to 20% of the available torsional strength, Tn/Omega, the torsional effects may be neglected. When Ta exceeds 20% of Tn/Omega, the interaction of torsion, shear and flexure force shall be limited, using the interaction equation.