Tips & Tricks

July 29, 2025

Slab vs. Spread Footing in RISAFoundation: What's the Difference?

We often get asked: “Should I model my foundation as a slab or a spread footing in RISAFoundation?” While both are valid options, they use very different analysis methods, and the results can vary accordingly. In this article, we’ll walk through a side-by-side comparison, using the same modeled conditions to highlight how the results differ — and why. Model Setup To keep things consistent, we modeled a single condition in two ways: once with a spread footing and once with a mat slab. Mat Dimensions: 10' x 10' x 1' Pedestal: 1' x 1' x 2' Loads Applied: 40 k vertical dead load 10 k lateral dead load 15 k lateral wind load 14.79 k concrete self-weight Soil Overburden: Set to 0 for both elements Slab Mesh Size: Refined below default for more detailed results Load Combinations: A basic set used for clarity (see screenshots in RISAFoundation) Analysis Methodology Feature Spread Footing Slab Element Analysis Type Rigid body Finite Element Analysis (FEA) Support Model Single support point Compression-only springs (based on subgrade modulus) Mesh Behavior No submesh Submeshed into smaller plate elements Lever Arm for Lateral Loads Spread Footings: Full pedestal height + full footing thickness Slabs: Full pedestal height…

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Slab on Grade Design with RISAFoundation
April 15, 2014

Slab on Grade Design with RISAFoundation

RISAFoundation was originally created as mat slab design software, but with some tweaks in the latest version (v6.0) it is now useful for slab on grade design as well. To get a design for slab on grade simply draw a slab element which has the appropriate thickness:

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How to Add a New Pattern to the Moving Load Database
February 18, 2014

How to Add a New Pattern to the Moving Load Database

RISA-3D and RISA-2D come with a default list of existing moving load patterns. These are listed in the Moving Loads Library which can be viewed by clicking on the Moving Load Patterns button in the Advanced tab.

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How to model a Geodesic Dome in RISA-3D?
February 5, 2014

How to model a Geodesic Dome in RISA-3D?

In modeling what would be a rather difficult geometric structure, by using the Templates database in RISA-3D, a geodesic dome can be constructed rather quickly and easily.

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Designing Built-Up Sections using RISA-3D
January 2, 2014

Designing Built-Up Sections using RISA-3D

Use RISASection to find the properties of built-up steel sections, then model beams using the same section properties in RISA-3D and get full code-checks using AISC 360. This webinar will teach you how to use RISASection quickly and easily to determine complex section properties.

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How Do I Model a Tapered Pipe?
December 30, 2013

How Do I Model a Tapered Pipe?

Tapered members are common for metal buildings and pole-type structures. For tapered wide flange members RISA provides a quick way to generate a tapered section that can then be checked per the provisions of AISC Design Guide 25 on tapered wide flanges.

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What are Web Doubler plates used for in RISAConnection?
December 27, 2013

What are Web Doubler plates used for in RISAConnection?

For moment connections in RISAConnection there is an option to place web doubler plates on the column web. These plates act as a reinforcement for the column web to prevent panel zone shear failure. As shown below, when the flanges of a beam in a moment connection connect to a column they form a...

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