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AISC 341-22 Special Moment Frame — Column–Beam Moment Ratio

§E3.4a strong-column/weak-beam: ΣM*_pc/ΣM*_pb > 1.0 (LRFD). Columns: Z_c(F_yc − P_rc/A_g), optionally projected to the beam centerline. Beams: AISC 358 probable moment M_pr = C_prR_yF_yZ_e plus the shear-amplification moment M_uv. Since AISC 341-16 the beam side uses C_pr — not the older 1.1R_yF_yZ. Turkish counterpart: ÇYTHYE/TBDY strong-column tools.

Column (same section above and below)

Grade

Z_x in³

A_g in²

d_c in

P_rc column above kip

P_rc column below kip

Columns at joint

Beams

Grade

Z_e at hinge in³

d_b in

Beams at joint

L — column centerline span ft

S_h — hinge from column face in

w_u (gravity with E) kip/ft

Story height above in

Story height below in

Results

M_pc per column · projection—

C_pr · R_y · M_pr AISC 358 §2.4.3—

L_h · V_pr · M_uv—

ΣM*_pc / ΣM*_pb §E3.4a—

§E3.4aΣM*_pc/ΣM*_pb > 1.0; M*_pc = Z_c(F_yc − α_sP_rc/A_g) projected to the beam centerline (factor h/(h − d_b)); M*_pb = M_pr + M_uv at the column centerline

AISC 358M_pr = C_prR_yF_yZ_e, C_pr = (F_y + F_u)/(2F_y) ≤ 1.2 (A992: 1.15); V_pr = 2M_pr/L_h + w_uL_h/2; M_uv = V_pr(S_h + d_c/2). S_h depends on the prequalified connection (RBS: a + b/2).

Table A3.2R_y: A992 and A572 Gr 50 = 1.1; A36 = 1.5

VerifyHand calculation (regression test): W24×76 beams both sides (Z = 200 in³), W14×257 column (Z = 487 in³, A = 75.6 in², d = 16.4 in), P_r = 600 kip, L = 30 ft, S_h = 11.95 in, w_u = 1.2 kip/ft → M_pr = 12,650 kip-in, ratio = 1.406 (unprojected). Formulas: Elsevier, Results in Engineering (2022); Tekla; ideCAD.

ScopeLRFD only. The §E3.4a exceptions, panel-zone shear (§E3.6e), width-to-thickness limits (Table D1.1) and connection design (AISC 358) are separate checks.

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.