Rectangular Isolated Footing in SDC D per ACI 318-25

Summary: Design rectangular footing for column in Seismic Design Category D. Free structural design software. ACI 318-25 §19.2.1.1 requires minimum f'c=3000 psi…

Overview

Building / scenario

• Geometry / size: 10 ft × 6 ft

Problem statement

A rectangular column footing 10 ft × 6 ft, 14 in. thick. Column load 100 kip D + 50 kip L. SDC D. Per ACI 318-25 §19.2.1.1, minimum f'c = 3000 psi for foundations. Soil 3000 psf. Check flexure, shear, development length.

Workflow in StructSuite

StructSuite's free foundation design tool. Geometry: rectangular (Lx=10, Ly=6), thickness 14 in. Loads: D, L. Materials: q_allow=3000 psf, f'c≥3000 psi (SDC D), reinforcement. ACI 318-25 §19.2.1.1 exception: 2500 psi permitted for residential 2-story stud bearing in SDC D. Rectangular footing: different reinforcement each direction.

Design considerations (excerpt)

Rectangular when column aspect > 1 or space constraints. Ly=6 ft (short) vs Lx=10 ft—flexure critical in long direction. Thickness 14 in.: punching shear often governs; increase thickness to reduce stress. 10×6 under 150 kip: q ≈ 2.5 ksf; check one-way shear each direction.

150 kip (100 D + 50 L) from column. SDC D: add E for seismic; 0.9D+1.0E may reduce bearing, increase overturning. Gravity-dominant buildings: D+L governs. Eccentricity from moment changes bearing distribution.

f'c=3000 psi minimum for SDC D per ACI §19.2.1.1. Higher f'c increases shear capacity (φVc ∝ √f'c) and reduces thickness. 3000 psi most common for footings; 4000 psi for heavier or high shear. Residential…

Related terms

• StructSuite
• structural engineering
• design example
• foundation
• ACI 318
• rectangular isolated sdc

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