ASDIP RETAIN is a structural engineering software for design of retaining walls. Usually, a retaining wall needs a footing reinforced at top and bottom. However, for small retaining walls, a footing with a single layer of reinforcement may be good enough. This document is a step-by-step overview of the design of a single-layer wall footing example using ASDIP RETAIN.
Single-layer wall footing example
As an example, let’s consider the 6'-0" tall masonry retaining with a flat backfill shown below. The water table is located below the base of the structure. Design the optimum dimensions and find out if a footing with a single layer of reinforcement is adequate.
Entering the wall geometry and loads
In the Geometry tab specify 9 rows of 8"-thick concrete masonry blocks and enter the flat backfill height as 6'-0", The geometry will depend on the stability and strength results, so this is an iterative process. For now, let's assume toe length = 1'-6" and heel length = 1'-6". Note that since the minimum Ldh = 6" for the stem rebars and the concrete cover is 3", the minimum footing thickness is 9".
Go to the Loads tab to enter the loads on the wall as defined above. Enter the backfill density and internal friction angle and select Coulomb as the lateral soil pressure theory. In addition, specify the water table height as zero. No other loads are acting on the wall.
The At-a-Glance tab shows a summary of the results. At this point we can see that the stability with the proposed dimensions is OK, with safety factors for overturning and sliding of 2.84 and 2.02 respectively. The image below shows the Geometry tab, and a view of the Graph > Footing tab with information of the bearing analysis under factored loads, with the controlling load combinations in flexure and shear.
ASDIP RETAIN generates a condensed report in the Condensed tab, showing detailed calculations organized by topic in a tabular format This is excellent for a deeper check of the design as you go.
Specifying the reinforcement
Since this is a relatively small retaining wall, let's try to use a single-layer wall footing. Go to the Reinforcement tab and specify the rebars for the masonry wall as #4 @ 16". Note that a larger bar diameter might impact the footing thickness due to the hook development length requirements. Go to the Reinforcement > Footing tab and check mark the corresponding check box at the top. Then enter the footing rebars as #4 @ 12" in each direction.
The image below shows the Reinforcement tab, and a graphic view the construction details of the retaining wall showing the rebars and the wall dimensions. Note that all the reinforcement design checks pass in the At-a-Glance tab.
ASDIP RETAIN generates a detailed presentation of the results in the Detailed tab, showing step-by-step calculations organized by topic and load combination, with exposed formulas and references to the design code. This is excellent for a deep granular check of the design.
Takeaway
ASDIP RETAIN includes the design of retaining wall footings with either a single or a double layer of reinforcement. This step-by-step design example shows how fast the design can be completed and optimized using ASDIP RETAIN. The results are shown instantly in both text and graphics format for an immediate granular check.
For our collection of blog posts about retaining wall design please visit Retaining Wall Design.
Detailed information is available about this structural engineering software by visiting ASDIP RETAIN. You are invited to download the Free 15-day Software Trial or go ahead and Place your Order.
Best regards,
Javier Encinas, PE
ASDIP Structural Software