ASDIP Retain – Cantilever Retaining Wall Design

ASDIP Retain
About ASDIP Retain:   Overview | Benefits | Features | Documentation
Modules:   Cantilever Retaining Wall Design | Restrained Retaining Wall Design

 

Retaining structures hold back soil or other loose material where an abrupt change in ground elevation occurs. The retained material or backfill exerts a push on the structure and thus tends to overturn or slide it, or both. The cantilever is the most common type of retaining wall and is used for walls in the range of 10 to 25 ft in height. The stem, heel and toe of such a wall acts as a cantilever beam.

The design involves two major steps: the first one is the evaluation of the stability of the whole structure under the service loads, which includes the overturning and sliding failure modes, and the second one is the design of the different components, such as the stem, heel, toe and key, for bending and shear, under the combined factored loads.

This module computes the soil bearing pressures and analyzes the stability of the structure. In addition, the stem can be either concrete or masonry. It performs the concrete design based on the Ultimate Strength Design Method of the ACI 318, and the masonry design per the MSJC. The lateral pressures are calculated either per the Rankine, Coulomb or Equivalent Fluid theories. Seismic design as per the Mononobe-Okabe approach. Load combinations per the latest IBC / ASCE 7.

Cantilever Retaining Wall DesignInput Data

The input data required includes the geometry of the backfill, stem, toe, heel and key. In addition, the program accepts a number of load cases, such as surcharge (strap, uniform and/or concentrated), wind and seismic. The reinforcing steel may be specified and customized using multiple options.

Example

As an example, consider a concrete retaining wall with a 16-ft high stem that holds a 14-ft high backfill, which is sloped 10 degrees. Apply a uniform surcharge of 100 psf. The wall is exposed to a wind load of 30 psf and it’s located in a seismic zone where kh = 0.15. Per the sois report, the allowable soil bearing pressure is 4.0 ksf.

Design the retaining wall for a minimum overturning and sliding safety factors of 1.5. In addition, find the steel reinforcement to satisfy the strength requirements of all the controlling load combinations. Conservatively, ignore the soil bearing pressure in the heel design.
Cantilever Retaining Wall Design Example

Cantilever Retaining Wall Design LoadsOutput

The program checks the wall stability for the service combined loads and performs the concrete design of the stem, toe, heel and key for the factored combined loads. In each particular case the controlling load combination is identified and reported.

A detailed step-by-step report is available to the touch of a tab, which is updated with every new change. In addition, ASDIP Retain uses a pre-formated colorful text-with-values output for easier identification of the problem areas.

ASDIP Retain generates a graphical view of the designed retaining wall and the resulting pressures and forces, as shown. The program also generates the moment and the shear diagrams for every load combination, as well as a view of the construction section and elevation with the reinforcement information. Note that the rebars can be easily optimized this way.

In this example, the bearing pressures are less than the allowable limit, and both the overturning and sliding safety factor are greater than 1.5, therefore the stability is OK. Note that the factored shear forces are calculated in each component, and then they are compared to the corresponding design shear strength. The maximum bending moments are also calculated and compared to the flexural strength. The proposed dimensions and the reinforcing steel are therefore adequate.

Cantilever Retaining Wall Design DiagramsCantilever Retaining Wall Reinforcement Design

 

 

 

 

 

 

 

Explore ASDIP Retain

About ASDIP Retain:   Overview | Benefits | Features | Documentation
Modules:   Cantilever Retaining Wall Design | Restrained Retaining Wall Design