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ACI 318-19 Special Moment Frame Column — Capacity-Design Shear

§18.7.6: V_e from the column's probable moment M_pr (1.25f_y, φ = 1) — the largest M_pr over the range of factored axial loads — capped by the shear the beams can deliver and not less than the analysis shear. M_pr comes from strain compatibility; its nominal (1.0f_y) path is checked against StructurePoint's spColumn example.

Column section

b in

h (bending direction) in

Cover to bar center in

f′c psi

f_y

Bars per face

Size

Side bars per side

Demand

P_u,min kip

P_u,max kip

Clear height ℓ_u in

V_u from analysis kip

ΣM_pr beams, top joint kip-ft

ΣM_pr beams, bottom joint kip-ft

Hoop bar

Legs parallel to V

Results

Max M_pr over P_u range · at P kip-ft · kip—

V_e from column M_pr · beam cap kip—

Design V_e §18.7.6.1.1—

V_c · V_s required kip—

Hoop spacing for shear—

§18.7.6.1.1V_e = (M_pr,top + M_pr,bot)/ℓ_u with the largest M_pr over the factored axial range; need not exceed the shear from the beams' M_pr (here: half of ΣM_pr at each joint, equal columns above and below); not less than V_u

§18.7.6.2.1V_c = 0 within ℓ_o only if the earthquake shear ≥ ½ of the required shear and P_u < A_gf′c/20; otherwise V_c per Table 22.5.5.1 with axial compression

VerifyNominal path (1.0f_y, φ = 1) vs. spColumn (16×16 in, f′c 5 ksi, 4 #9 per face): pure bending 237.68 kip-ft, balanced (P = 416.8 kip) 385.8 kip-ft, f_s = 0 point 261.3 kip-ft — all reproduced. M_pr at P = 0: 292.1 kip-ft by an independent hand solution of the equilibrium equation.

ScopeSymmetric rectangular section, uniaxial bending. Combine with the confinement tool (§18.7.5): the smaller hoop spacing governs.

Preliminary calculation tool. Final design requires the full text of ACI 318 and review by a licensed PE. This tool follows ACI 318-19, the edition referenced by the 2021 and 2024 IBC; ACI CODE-318-25 was published in January 2025 and is expected in the 2027 IBC (changes include development length equations and seismic provisions).