ASDIP RETAIN is a structural engineering software for design of retaining walls. ASDIP RETAIN includes the design of top-restrained retaining walls, also called basement walls, based on the latest ACI 318 and AASHTO provisions.
The design of retaining walls may become time-consuming, since the calculations involve multiple load types and combinations, fixity conditions, and the application of the Code provisions to design the reinforcement. This document is a step-by-step design example of a typical concrete basement wall using ASDIP RETAIN.
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Basement Wall Design Example
As an example, let’s consider a basement wall in a building, which is a restrained retaining wall with a level backfill, subject to the traffic surcharge load shown. Apply a vertical concentrated load on top of the stem as a reaction of the upper levels of the structure.
The water table occurs below the wall footing. Design the optimum dimensions and find the required reinforcement.
Basement Wall Geometry
In the Geometry tab enter the geometric information given in the statement of the example. The stem height is 10′-0″, and the stem thickness is 8" for a shear ratio of 0.85. The toe and heel lengths will depend of the stability and strength results, so this is an iterative process.
The image below shows the Geometry tab to the left, and a summary view with the most relevant result information. Note that the final toe and heel lengths are is 1.8' and 2.2' respectively.
Basement Wall Loads
In the Loads enter the loads on the wall as defined above. In this example the wall has a full height backfill, and a uniform traffic surcharge on top. In addition, the wall supports a concentrated load on top of the stem, due to the reactions of the upper floors.
The image below shows the Loads tab, and a graphical view of the bearing analysis with valuable information. Note that the maximum bearing pressure is 3.7 ksf and the allowable pressure is 4.0 ksf.
Basement Wall Materials
The next step is to enter the material properties. In this example the concrete strength is 4000 psi. This will affect the shear strength, and will control the thickness of the stem and footing. In this example the slab on grade at the bottom of the basement has been used to restrain the lateral movement of the wall, so a sliding failure is prevented.
The image below shows the Materials tab, and a graphical view the Stem pressures and diagrams. Note that the blue areas in the diagrams represent the structural capacity, for a quick graphical overview of the adequacy of the design.
Basement Wall Reinforcement
Go to the Reinforcement tab to specify the rebars for the wall. ASDIP RETAIN has multiple options to customize the reinforcement. The image below shows the Reinforcement tab and a construction view of the retaining wall with the design rebar sizes and spacing.
Please note that the stem has only one layer of rebars, located at the front face. The footing thickness was controlled by the required development length of the stem rebars.
ASDIP RETAIN includes the design of basement retaining walls, either concrete or masonry. This basement wall design example shows that the whole process can be completed and optimized in just a few minutes with the help of ASDIP RETAIN, which otherwise would be very cumbersome and time-consuming.
Detailed information is available about this structural engineering software by visiting ASDIP RETAIN. For engineering background, please see my blog post Restrained Retaining Walls: A Design Overview. For our collection of blog posts about retaining walls please visit Structural Retaining Wall Design.
Javier Encinas, PE
ASDIP Structural Software