Wall Footing (ACI 318-19)

How it calculates

The Wall Footing (ACI 318-19) calculator designs continuous strip footings per ACI 318-19, with load combinations from ASCE 7-16 (IBC 2021) or ASCE 7-22 (IBC 2024). It checks bearing pressure under service loads, flexural reinforcement, one-way shear, and reinforcement development length.

Bearing pressure check (ASD, ASCE 7-16/22 Ch. 2)

Service loads are combined using ASD load combinations to compute the gross soil bearing stress q_s at each load case:

utilization = q_s / q_a ≤ 1.0

Stability checks for sliding (FS_s), overturning (FS_ovt), and uplift are also reported under service loads.

Flexural design (ACI 318-19, Cl. 22.2)

Factored moment demand M_u is calculated at the critical section (face of the wall) from the net upward soil pressure under the LRFD load combinations. Required flexural reinforcement area A_s is compared to the provided area and to the minimum reinforcement:

A_s,min = 0.0018 × H × b (per ACI 318-19, Cl. 7.6.1)

utilization = M_u / (phi × M_n) ≤ 1.0

Compression reinforcement is not considered in bending strength calculations.

One-way shear (ACI 318-19, Cl. 22.5)

The critical shear plane is taken at distance d (effective depth) from the wall face. Shear capacity phi × V_c uses the concrete shear strength formulation per ACI 318-19:

utilization = V_u / (phi × V_n) ≤ 1.0

No shear reinforcement is included.

Development length (ACI 318-19, Cl. 25.4)

Available development distance is l_a = B/2 - b/2 - cover. Required development length l_d is calculated per ACI 318-19 and reduced for excess reinforcement area (A_s,reqd / A_s,provided). If development length is insufficient, the calculator automatically checks whether a plain concrete design is adequate.

Top (negative moment) reinforcement

For cases with overturning moments generating tension at the top of the footing, top bar reinforcement is also checked for negative bending capacity and development length.

Assumptions

Wall is centred on the footing. Lateral loads are only used for the sliding check. No shear reinforcement is considered. Wall reinforcement is assumed to continue directly into the footing (interface is not checked). There are no significant changes between IBC 2021 and IBC 2024 or between ASCE 7-16 and ASCE 7-22 that affect this calculation.