SteelInfo

Steel beam calculator

Check a simply supported or cantilever steel beam to AS 4100:2020. Enter the span and loads to get the design moment and shear, the member moment capacity with lateral-torsional buckling, shear capacity and deflection, and the lightest sections that pass.

Beam i Span L (m) i Section to check i

Loads (unfactored)

UDL, dead G (kN/m) i UDL, imposed Q (kN/m) i Include self-weight i

Point loads i
	Dead G (kN)	Imposed Q (kN)	Position a (m) from the left support
P1
P2
P3

Lateral restraint

Compression flange restraint i Restraint type i Load height i α_m override i

Serviceability

ψ_s i Deflection limit, span / i

Search for the lightest sections i

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Method

Design actions (AS/NZS 1170.0): strength combinations 1.35G and 1.2G + 1.5Q, with the beam's self-weight in G. Moments and shears by statics; the larger of the two combinations governs each check.
Bending (AS 4100 Cl. 5.6): each segment between restraints is checked with l_e = k_tk_lk_rl (Cl. 5.6.3, Tables 5.6.3(A)–(C)), α_m from the Cl. 5.6.1.1 quarter-point formula or Table 5.6.2, and φM_b = φα_mα_sM_s ≤ φM_s. Segments short enough for full lateral restraint (Cl. 5.3.2.4, β_m = −0.8 with transverse loads, otherwise −1.0) use φM_s. k_r is taken as 1.0.
Shear (Cl. 5.11): φV_v from the section tables.
Shear with bending (Cl. 5.12.3): V* ≤ φV_vm at every cross-section, where φV_vm = φV_v for M* ≤ 0.75φM_s and φV_v(2.2 − 1.6M*/φM_s) for larger moments.
Deflection: double integration of M/EI (E = 200 000 MPa) under G + ψ_sQ, compared with span / limit.
Not checked: web bearing and buckling at supports and point loads (Cl. 5.13), connections, torsion from loads off the shear centre, vibration, ponding, fire, and the rotation of a cantilever's back span. Continuous beams and other load cases (wind uplift, for example) are not covered.

Preliminary design aid only, not a substitute for a qualified engineer. See the disclaimer and data sources.