Design of a Simply Supported Steel Beam
This structural form is perhaps the most common structural element in practice and the easiest to do.
Whether you are designing a multi-storey steel building or a bridge beam or a oil rig framing platform, the
same procedures would apply.
The procedures to design a simply supported steel beam, typically an I-section, based on BS 5850 are
outlined below. Generally these procedures would apply to any codes of practice :-
- Prepare Sketches of Structural Forms/Diagrams/Forces
- Evaluate Actual Dead and Life Loads (earth, concrete, footpath, etc)
- Evaluate Load Factors (1.4, 1.6 for Normal Steel Design, Combination in Bridge Design)
- Evaluate Factored Loads (Ultimate Dead & Life Loads)
- Calculate Moments, Shears, Axial for both Service and Ultimate Limit State.
- Prepare Bending Moment, Shearing Force and Axial Force Diagrams.
- Determine Preliminary Sizes of Beam, using Moment Capacity, if maximum moment controls
or Buckling Capacity if Torsional forces controls.
- Choose a Trial Section and Design for Bending.
- Check Classification of Section - Compact, Semi-Compact, or Slender
- Check for compliance to :-
- Shear Buckling
- Combined Moment and Shear (Max Moment + Shear and Max Shear + Moment)
- Deflection under Service Loads
- Bearing & Buckling of Web at Supports
If Items 8, 9 and 10 are complied with the design code requirements, then the chosen beam is
satisfactory, if not, then either change sizes of beams, spacing of beams, or strengthening and stiffening of
affected sections of the beam be made.
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Authur- Philip Goh (B.Sc, MIEM, P.Eng. MICE,
MEC Engineers, Civil & Structural Engineer