Shallow Foundation per ACI 318-19 with ideCAD

How does ideCAD design single footing, strip footing, and mat foundations according to ACI 318-19?

• Single footing, strip footing, and mat foundations are designed automatically according to ACI Chapter 13.

Notation

A_g = gross area of concrete section, in²
A_s = area of nonprestressed longitudinal tension reinforcement, in²
E_c = modulus of elasticity of concrete, psi
E_s = modulus of elasticity of reinforcement, psi
f_c^' = specified compressive strength of concrete, psi
f_y = specified yield strength for nonprestressed reinforcement, psi
M_u = factored moment at section, in.-lb
β = ratio of long to short dimentions; clear spans for two-way slabs, sides of column, concentrated load or reaction area; or sides of a footing
γ_s = factor used to determine the portion of reinforcement located in center band of footing

According to ACI 13.3.1.2, the bottom reinforcement's minimum foundation effective depth is 6 inches.

According to ACI 13.3.1.3, in sloped, stepped, or tapered foundations, the depth, and location of steps or slope angle should be such that design requirements are satisfied at every section.

One-way Shallow Foundations

According to ACI 13.3.1.4, one-way shallow foundations, including strip footings, combined footings, and grade beams, should be designed in accordance with the applicable provisions of ACI Chapter 7 (One-Way Slab Design per ACI 318-19 §7) and ACI Chapter 9 (Reinforced Concrete Beam Design per ACI 318-19 per ACI 318-19 §9, §18).

According to ACI 13.3.1.5, reinforcement should be distributed uniformly across the entire width of a one-way footing.

Two-way Isolated Foundations

According to ACI 13.3.3.1, two-way shallow foundations should be designed in accordance with the applicable provisions of ACI Chapter 7 (One-Way Slab Design per ACI 318-19 §7) and ACI Chapter 8 (Two-Way Slab Design per ACI 318-19 §8).

According to ACI 13.3.3.2, reinforcement should be distributed uniformly across the entire width of two-way footing in both directions.

According to ACI 13.3.3.3; in rectangular footing, reinforcement should be distributed in accordance with two conditions given below;

• Reinforcement in the long direction should be distributed uniformly across the entire width of the footing.

• Reinforcement in the short direction, a portion of the total reinforcement, γ_sA_s, should be distributed uniformly over a band equal to the length of the short side of the footing, centered on the centerline of the column or pedestal. The remainder of reinforcement required in the short direction, (1-γ_s)A_s, shall be distributed uniformly outside the center bandwidth of footing, where γ_s is calculated by ACI Eq. (13.3.3.3),

Two-way Combined Footings and Mat Foundations

According to ACI 13.3.4.1, two-way shallow foundations should be designed in accordance with the applicable provisions of ACI Chapter 8 (Two-Way Slab Design per ACI 318-19 §8).

According to ACI 13.3.4.3, the distribution of bearing pressure under combined footings and mat foundations should be consistent with the properties of the soil or rock and the structure and with established principles of soil or rock mechanics.

According to ACI 13.3.4.4, the minimum area of flexural reinforcement in nonprestressed mat foundations is satisfied near the tension face of the slab in the direction of the span, A_s,min=0.0018A_g

Walls as Grade Beams

According to ACI 13.3.5.1, walls as grade beams should be designed in accordance with the applicable provisions of ACI Chapter 9 (Reinforced Concrete Beam Design per ACI 318-19 per ACI 318-19 §9, §18).

According to ACI 13.3.5.3, walls as grade beams should satisfy the minimum reinforcement requirement of ACI 11.6.

According to ACI 11.6.1, If in-plane V_u ≤ 0.5ϕα_cλ√f_c‘A_cv, minimum ρ_l, and ρ_t should be in accordance with ACI Table 11.6.1.

According to ACI 11.6.1, If in-plane V_u ≤ 0.5ϕα_cλ√f_c‘A_cv, two conditions given below should be satisfied;

• ρ_l should be at least the greater of the value calculated by ACI Eq. (11.6.2) and 0.0025
  

• The minimum value of ρ_t should be 0.0025

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