Cantilever Retaining Wall (ACI 318-14)
Design cantilever retaining walls to ACI 318-14 and IBC 2018 with Rankine active earth pressure, overturning, sliding, and bearing stability checks, then stem and footing reinforcement design with code references. This is the legacy code edition for projects under ACI 318-14. Use the IBC 2021 or IBC 2024 version for new work.
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What it calculates
Design cantilever retaining walls to ACI 318-14 and IBC 2018. Rankine active earth pressure with overturning, sliding, and bearing checks, followed by stem and footing reinforcement design. For new projects, use the IBC 2021 or IBC 2024 version.
Code standards
- IBC 2018
- ASCE 7-16
How it calculates
The Cantilever Retaining Wall (ACI 318-14) calculator designs freestanding cantilever retaining walls in reinforced concrete to IBC 2018 and ACI 318-14. Rankine active earth pressure theory is used with retained soil in the active state and passive soil at the toe for sliding resistance. No shear key is modelled.
Lateral earth pressure (Rankine active theory)
Active lateral earth pressure coefficient K_a and passive coefficient K_p are computed from the soil internal friction angle phi:
K_a = tan²(45° - phi/2) K_p = tan²(45° + phi/2)
Lateral pressure varies triangularly with depth. Surcharge loads (dead and live) contribute a uniform lateral pressure component. The resulting lateral force H_total and its line of action are used for the stability checks.
Stability checks
Sliding: Total horizontal force H_total is compared to total resistance (base friction + passive soil at toe):
FS_sliding = F_resist / H_total ≥ 1.5
Overturning: Restoring moment from soil and wall dead loads about the toe is compared to the overturning moment:
FS_overturn = M_restore / M_overturn ≥ 1.5
Bearing: Maximum bearing pressure q_max at the footing base (trapezoidal or triangular distribution depending on resultant eccentricity) is checked against the allowable bearing capacity q_a.
Stem flexural and shear design (ACI 318-14, Cl. 21.2 and 22.5)
The governing moment M_u,stem at the base of the stem and shear demand V_u,stem are calculated from the factored lateral soil and surcharge loads per IBC 2018 LRFD combinations:
utilization = M_u,stem / (phi × M_n,stem) ≤ 1.0 utilization = V_u,stem / (phi × V_n,stem) ≤ 1.0
where phi = 0.90 for flexure and 0.75 for shear. Temperature and shrinkage reinforcement requirements per ACI 318-14 Cl. 24.4.3.2 are also reported.
Heel and toe design (ACI 318-14, Cl. 22.2)
Separate moment and shear checks are performed for the heel (resisting net upward pressure behind the stem) and toe (resisting upward bearing pressure in front of the stem):
utilization = M_u,heel / (phi × M_n,heel) ≤ 1.0 utilization = M_u,toe / (phi × M_n,toe) ≤ 1.0
Assumptions and scope
Backfill is flat with no slope. Only dead/live surcharge, wall self-weight, and soil loads are considered. No shear key is included. Wind and seismic loads are not modelled. Concrete detailing must be checked separately.
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
I like that Calcs.com shows the code reference section for each calculation and function. That means every time I use it, there's a potential for me to learn something.
Jim Fanjoy
Project Architect, Brittell Architecture
Frequently asked questions
What design standards does this calculator use?
What are the key inputs?
What stability and strength checks does the calculator perform?
Does this calculator include a shear key?
How does this version differ from the IBC 2021 and IBC 2024 versions?
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