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AISC 341-22 Width-to-Thickness Limits — I-Shaped Beams & Columns

Table D1.1b for highly ductile (SMF, SCBF) and moderately ductile (IMF) members. AISC 341-22 returned the coefficients to the 2010 values: the highly ductile flange limit is now 0.30√(E/(R_yF_y)) — stricter than the 0.32 of AISC 341-16 (A992: 6.89 instead of 7.35). The new moment-frame web limit (Case 11) is shown provisionally: only one secondary source was found for its coefficients.

Section

Grade

Ductility

b_f in

t_f in

d in

t_w in

h/t_w from tables

A_g in²

P_r (compression) kip

Results

Flange b_f/2t_f vs limit Case 7—

(AISC 341-16 flange limit, for comparison)—

C_a = P_r/(R_yF_yA_g)—

Web h/t_w vs limit — PROVISIONAL Case 11—

The web limit uses λ = 2.5 (highly) / 5.4 (moderately) × √(E/(R_yF_y)) × (1 − C_a)^2.3, found in a single secondary source (Tekla Structural Designer's compilation of Table D1.1b). AISC's own article confirms that Case 11 is new and regression-based but does not print the coefficients. Confirm against AISC 341-22 Table D1.1b before relying on it; it is not part of the verdict above.

Case 7Flanges of rolled or built-up I-shapes: λ_hd = 0.30√(E/(R_yF_y)), λ_md = 0.38√(E/(R_yF_y)). Sources: Modern Steel Construction, Nov. 2022 (L. Geschwindner) and Tekla.

VerifyA992 highly ductile flange limit: 7.22 (341-10) → 7.35 (341-16) → 6.89 (341-22); A36 in 341-16: 7.42 — all four values reproduced (regression test). AISC notes the 2022 limit excludes 71 W-shapes, against 54 before.

ScopeI-shaped beams and columns of moment frames. Diagonal braces (Table D1.1a), HSS and built-up box sections are not included.

Preliminary calculation tool. Final design requires the full text of the referenced standard (see the sources on this page) and review by a licensed PE.