Cantilever Retaining Wall (IBC 2024)
Design cantilever retaining walls to the current IBC 2024 standard with choice of EFP, Rankine, or Coulomb lateral earth pressure. Covers concrete and CMU stems with overturning, sliding, bearing, and flexural reinforcement checks to ACI 318-19 and TMS 402-22. Seismic loads go in via EFP analogy.
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What it calculates
Design cantilever retaining walls, concrete or CMU, to IBC 2024, ASCE 7-22, ACI 318-19, TMS 402-22, and CMU-TEC-001-23. Choose Equivalent Fluid Pressure, Rankine, or Coulomb for lateral earth pressure. Includes shear key design and seismic loads via EFP analogy.
Code standards
- IBC 2024
- ASCE 7-22
- ACI 318-19
- TMS 402-22
- CMU-TEC-001-23
How it calculates
The Cantilever Retaining Wall (IBC 2024) calculator designs freestanding cantilever retaining walls in reinforced concrete or CMU to IBC 2024, ASCE 7-22, ACI 318-19, TMS 402-22, and CMU-TEC-001-23. Three lateral earth pressure methods are supported. Retained soil is assumed to be in the active state; passive soil at the toe provides sliding resistance.
Lateral earth pressure
Three lateral earth pressure methods are supported:
- Equivalent Fluid Pressure (EFP) - user enters an equivalent fluid unit weight; triangular pressure distribution is computed directly
- Rankine active theory - K_a = tan²(45° - phi/2); lateral pressure = K_a × gamma_s × height
- Coulomb active theory - accounts for soil-wall friction angle delta and backfill slope angle beta
Seismic lateral loads can be added using the EFP analogy per ASCE 7-22 (additional seismic EFP combined with static earth pressure for seismic load combinations). Water table effects are modelled with modified effective unit weights.
Stability checks
Sliding: Total sliding force H_total is compared to total resistance (base friction + passive soil resistance + shear key passive resistance if present):
FS_sliding = F_resist / H_total ≥ 1.5
Overturning: Restoring moment (from soil and wall dead loads) is compared to the overturning moment about the toe:
FS_overturn = M_restore / M_overturn ≥ 1.5
Bearing: Maximum soil pressure q_max at the footing base is checked against allowable bearing q_a.
Stem design (ACI 318-19, Cl. 22.2 and 22.5, or TMS 402-22, Cl. 9.3)
The governing moment M_u,stem and shear V_u,stem at the base of the stem are calculated from the factored lateral soil loads per IBC 2024 LRFD combinations:
utilization = M_u,stem / (phi × M_n,stem) ≤ 1.0 utilization = V_u,stem / (phi × V_n,stem) ≤ 1.0
For CMU stems, TMS 402-22 allowable stress provisions are applied. Masonry is assumed fully grouted CMU.
Heel, toe, and shear key design (ACI 318-19, Cl. 22.2)
Separate moment and shear checks are performed for the heel and toe. If a shear key is specified, flexural and shear capacities of the key section are checked separately:
utilization = M_u,key / (phi × M_n,key) ≤ 1.0 utilization = V_u,key / (phi × V_n,key) ≤ 1.0
Assumptions and scope
Backfill is flat with no slope. Only dead/live surcharge, wall self-weight, and soil loads are considered. Concrete detailing must be checked separately. Expansive soils and flowing water effects are not modelled.
What engineers say
Just the simple feature of being able to link loads is a really big time-saver.
Sam Hensler
Principal, Dynamic Analysis Engineering Consulting
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Jim Fanjoy
Project Architect, Brittell Architecture
Frequently asked questions
What design standards does this calculator use?
What lateral earth pressure theories are supported?
What are the key inputs?
What stability and strength checks does the calculator perform?
How does this IBC 2024 version differ from the IBC 2021 version?
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