How to Design a Steel Beam to AS4100:1998

Scope

This sheet calculates maximum design actions and the associated capacities of a uniaxially loaded steel beam with multiple supports and loads. Maximum deflection is calculated along the length of the beam and can be either upward or downward.

General Notes

  • The main outcome of this sheet is to design for a steel beam against moment, shear and deflection. The steel beam is assumed to be uniaxially loaded.
  • The supports for the steel beam are assumed to be pinned (hinged) or fixed supports and can be located anywhere along the beam. A minimum of 2 pinned or 1 fixed supports are required and they do not necessarily need to be at either end of the beam.
  • Reaction forces are calculated for dead and live loads on all supports
  • Sign Convention: The following diagram illustrates the positive sign convention for loads and outputs

Loading_Sign_Convention.svg 

  • Information/inputs required from the user:
    • Dimensions and Member Section Properties
      • Selected member for steel beam
      • Span Length in mm
      • Effective length, in mm
      • Location of supports in tabular form. If the first support is not at 0, it is assumed that the left-hand side of the beam is cantilevered. If the last support input is not equal to the length of the beam, the beam is cantilevered.
    • Patch Load Table
      • Magnitude of the permanent portion of the patch load in kN/m
      • Magnitude of the imposed portion of the patch load in kN/m
      • Start location of the patch load from the left-hand side in mm
      • End location of the patch load from the left-hand side in mm
    • Point Load Table
      • Magnitude of the permanent portion of the point load in kN
      • Magnitude of the imposed portion of the point load in kN
      • Location of the point load from the left-hand side in mm
    • Applied Moment Load Table
      • Magnitude of the permanent portion of the applied moment load in kNm
      • Magnitude of the imposed portion of the applied moment load in kNm
      • Location of the applied moment load from the left-hand side in mm
    • Self-weight toggle
      • User specifies if self-weight is applied to the analysis.
    • Limit state of analysis – Strength or Serviceability load case for analysis
    • Character of imposed actions (live loads) as per AS1170.0
    • Deflection limit factor, ka where deflection is compared using AS1170.0 (Span/k­a) and maximum absolute deflection limit (mm)

Assumptions and Limitations

  • The beam is analysed according to the specified geometry with up to 10 pin supports, located anywhere along the beam. This is solved for indeterminacy as well. Maximum moments, shear and deflection are calculated. It is not checked for combination actions
  • All lengths are calculated and expected to be specified from the left-hand side of the beam. This includes the entire length of the span and the location of the supports, the applied loads and moments.
  • Judgement is required for the use of the beam. Roof and floor uses is permissible and chosen by its character of imposed action.
  • Only sections available from OneSteel Seventh Edition Hot Rolled Structures are available for analysis.
  • Non-uniform stresses in sections is assumed to occur in SHS and RHS and is assumed to follow the design capacity guidelines as specified by AusTubeMills Design Capacity Tables Part 5
  • Beams are computed by a chosen limit state and load combination. It is up to the user to choose limit states to determine the worst loading case combination
  • P-Delta effects of long term deflection and moments are ignored for the purposes of the analysis

References

AS4100-1998 – Steel Structures

AS1170.0-2002 – Structural Design Actions: General Principles

AS1170.1-2002 – Structural Design Actions: Permanent, imposed and other actions

Gorenc, B.E. & Tinyou, R. & Syam, A. A. (2012) Steel Designer’s Handbook. Sydney, NSW:New South Publishing

OneSteel (2014) Seventh Edition Hot Rolled and Structural Steel Products. OneSteel Manufacturing

AustubeMills (2013) Design Capacity Tables for Structural Steel Hollow Sections. Australian Tube Mills

 

 

 

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