Rectangular Isolated Footing in SDC D per ACI 318-25

Example

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.

How StructSuite solves this

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.

Steps

1. Step 1: Geometry & Configuration

   Design consideration: 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.

   In StructSuite: Open Step 1: Geometry & Configuration. Under Footing type, select Isolated footing (column) or Strip footing (wall). In the Dimension Lx (ft) input box enter 10; in Dimension Ly (ft) enter 6; in Thickness of footing (in.) enter 14. For support, select Column and Concrete (or Masonry/Steel/Wood) and enter column dimensions.

2. Step 3: Load Definition (ASCE 7-22)

   Design consideration: 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.

   In StructSuite: Open the Load Definition section. Click Add load case. For each load case, use the Type dropdown to select D, L, Lr, S, W, E, etc. In the Axial (kips) input box enter the column or wall axial load. Repeat for all load cases. StructSuite applies ASCE 7-22 §2.2 load combinations for bearing, shear, and flexure.

3. Step 2: Materials & Reinforcement

   Design consideration: 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 2-story stud: 2500 psi permitted. q_allow from geotechnical—3000 psf typical stiff soil.

   In StructSuite: Open the Materials section. In Allowable bearing pressure (psf) enter the value from the geotechnical report or IBC Table 1806.2. In f'c (psi) enter the concrete strength (e.g., 2500). In fy (ksi) enter steel yield. For reinforcement, select bar size and count for X and Y directions. In cover (in.) enter 3 or per spec. ACI 318-25 §19.2.1.1 sets minimum f'c for SDC D, E, F.

Live design (pre-filled)

The form below is the real StructSuite module with example data loaded. Display only—values cannot be changed.