May 16, 2022

Retaining Wall Design in RISACalc

Learn how to load and design individual masonry and concrete retaining walls in RISACalc.

Tags: New, Retaining Walls, RISACalc

June 28, 2011 | RISAFoundation, New, Soil

Checking Soil Bearing in RISAFoundation

RISAFoundation has the capability to report soil bearing pressures, and check them against allowable pressures. In the Global Parameters, under the Solution tab, be sure to set an Allowable Bearing pressure. This allowable bearing will be used as a default for your entire RISAFoundation model, unless overridden by a soil region in a particular location. Note that the Subgrade Modulus will affect load distribution within the soil, so it is important as well. After solving, click on the dropdown next to the slab contours button, and choose Soil Pressure. The slabs are now shown with color contours representing the soil pressure. A color coding legend also appears in the upper right corner. Note that contours which are colored white have no soil pressure, and therefore represent areas of net uplift. For more detailed soil pressure results, check the Soil Pressures spreadsheet, which also includes a ratio of actual to allowable bearing…

February 20, 2024 | Concrete, RISAFoundation, New, Soil

Gross and Net Soil Pressures

In RISAFoundation, the Allowable Soil Bearing value is controlled by the Soil Region. This value is always taken as a Gross allowable soil pressure by default. Allowable Soil Bearing values are typically supplied by the Geotechnical Engineer as either Gross or Net allowable values. The Gross or Net Soil Pressure can be specified in the Footing Definitions spreadsheet under the Soil tab. In RISAFoundation, the option to choose between gross and net soil pressures is only available for footings. The soil bearing check in RISAFoundation uses the same load to check soil bearing (Footing Self-Weight + Overburden + Applied Load) regardless of whether a Gross or Net Soil Pressure is specified. The Gross Soil Pressure combines the upward pressure and the added pressure due to the applied load, equal to the applied load divided by the footing area. When a Gross Soil Pressure is specified, the load is compared directly against the Default Allowable Bearing (user-entered) value in the Soil Definitions Spreadsheet: For the Net Soil Pressure, the overburden and self-weight is canceled out by an equal and opposite upward pressure, leaving a Net Soil Pressure equal to the applied load divided by the footing area. When a Net soil…

March 6, 2025 | RISAFoundation, Soil, Piles

Pile Supported Slabs in RISAFoundation

Ensuring Your Slab is Fully Supported by Piles in RISAFoundation A common mistake when modeling pile-supported slabs in RISAFoundation is forgetting to zero out the soil properties. By default, RISAFoundation assigns a soil definition to all slabs, which introduces soil springs into the model. If not adjusted, this can lead to unintended load distribution, where the slab is partially supported by both the soil and the piles. To ensure your slab is fully supported by piles as intended, you must modify the soil definition. 📝 Important Note: While you should zero out the Subgrade Modulus and Allowable Bearing Pressure, don’t forget to define the Soil Depth Properties! These depth properties are essential for pile design—without them, your piles won’t have the necessary soil interaction data. RISAFoundation won’t throw an error, but the soil in that region will be ignored. For more details on soil depth properties, check out this article: Soil Properties in RISAFoundation. The Issue: Default Soil Properties Affect Load Distribution When defining a slab in RISAFoundation, the program automatically assigns a default soil definition, which includes a Subgrade Modulus and Allowable Bearing Pressure. If these values are left as-is, the slab will interact with the soil beneath it,…