Structures

Steel Beam Design: AISC 360-16

Check an IPE, HEA or HEB beam on a simple span or a cantilever to AISC 360-16 (flexure with lateral-torsional buckling, shear, deflection and the web at its bearings) or let it pick the lightest section that passes.

AISC 360-16ASCE/SEI 7-22EN 10365EN 10025-2IBCMetric

A rolled IPE, HE A or HE B from the EN 10365 catalogue, on a simple span or a cantilever, under dead and live line loads, up to two point loads and its own weight, combined by ASCE/SEI 7-22 §2.3 (LRFD) or §2.4 (ASD). Each section is classified by AISC 360-16 Table B4.1b and checked for yielding or flange local buckling (§F2.1, §F3.2), lateral-torsional buckling of every unbraced segment with C_b from Eq. F1-1 on its own moment diagram (§F2.2), shear (§G2.1), deflection against your limits and, when the beam bears on its supports, web local yielding and crippling (§J10.2, §J10.3). The answer comes first: which section passes, at what utilisation and what governs, or the lightest one of a family, or of all three, that passes.

The beam

ASCE/SEI 7-22 combinations: §2.3.1 for LRFD, §2.4.1 for ASD.

Loads

Point loads

Point load 1
Point load 2

Position a from the left support (a cantilever: from the fixed end). Leave the load at 0 for none.

Lateral bracing and deflection

Your own limits. IBC Table 1604.3 gives l/360 under live load for floor members; for a cantilever l is twice its length.

The checks

Check Utilisation

The section

Drawn to scale; EN axis y-y is the major axis (AISC x-x).
    PropertyValue

    The checks: Clause

    Check Clause Combination Demand Capacity Utilisation

    Unbraced segments: lateral-torsional buckling

    Segment From – to m L_b m M_max kN·m M_A / M_B / M_C kN·m C_b Range Utilisation

    Load combinations

    # Combination w kN/m M_max kN·m V_max kN Reactions kN
    The calculation step by step, with the numbers and the clauses
    Step Clause Equation and numbers Result

    Lighter and heavier sizes

    Section kg/m F_y MPa Utilisation Governing

    Export

    Convert units: Structural & steel

    Questions engineers ask

    How does it pick the lightest section?

    Choose Automatic in the section list, or the IPE, HEA and HEB family. Every size is run through the same checks with its own weight added and its own F_y, lightest first by mass per metre, and the first one whose every check is at or below 100% is the answer. The table under the result lists the lighter sizes that fail and the next ones that pass, and any of them can be taken with one press.

    How is lateral-torsional buckling checked, and where does C_b come from?

    Braces are placed at every L_b you give from the left support, or at the supports only, or the flange is taken as continuously braced. Each unbraced segment is checked to AISC 360-16 §F2.2 with its own length and with C_b from Eq. F1-1 on that segment of the moment diagram of each load combination, so a point load, a cantilever or bracing at third points each get their own C_b. A cantilever whose free end is unbraced takes C_b = 1.0. L_p and L_r use the torsion constant J and the warping constant C_w of the section.

    Why does an HEA section in S355 show flange local buckling?

    Because its flange is noncompact at that yield stress: b_f/2t_f of an HE 300 A is 10.7, above the limit 0.38√(E/F_y) = 9.1 of AISC 360-16 Table B4.1b. The nominal moment is then reduced by Eq. F3-1 below the plastic moment even when the beam is fully braced. IPE and HE B flanges are compact at the grades offered.

    Where do J and C_w of IPE and HE sections come from?

    EN 10365 does not tabulate them, so they are the ArcelorMittal Orange Book values, I_T and I_w, for each size. Every value was cross-checked against I_w = I_z (h − t_f)²/4 and the torsion constant formula with the root-fillet term, and all agree within 1.1%.

    Which yield stress does it use for S275 and S355?

    The minimum yield strength of EN 10025-2 for the thickness of the flange: S355 is 355 MPa up to 16 mm and 345 MPa from 16 to 40 mm, S275 is 275 and 265 MPa, S235 is 235 and 225 MPa. So an HE 300 B, with a 19 mm flange, is checked at 345 MPa in S355. ASTM A36 is 250 MPa, and A572 Gr. 50 and A992 are 345 MPa at every thickness.

    Which deflection limits does it use?

    Yours: one under live load and one under dead plus live load, both at service level. They start at l/360 and l/240; IBC Table 1604.3 gives l/360 under live load for floor members, and for a cantilever l is taken as twice its length.

    How do I know the numbers are right?

    The engine reproduces the AISC Design Examples for a W18×50 (φ_bM_n = 379 kip-ft continuously braced, and C_b = 1.01, M_n = 4,060 kip-in. and φ_bM_n = 305 kip-ft braced at third points) and the φ_vV_n = 306 kips of a W24×62 in shear. Every step of your own beam, with its numbers and clause, is under "The calculation step by step" and in the printed report.

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