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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User Defined Reinforcement
October 7, 2017

User Defined Reinforcement

RISAFloor ES v12 now includes the ability to manually define user reinforcement in concrete slabs.

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Eurocode Steel Design According to EN1993-1-1:2014 now Available
October 4, 2017

Eurocode Steel Design According to EN1993-1-1:2014 now Available

You can now set the L-Torque length for the EN1993-1-1:2014 code in RISA-3D and RISAFloor. In previous versions of the Eurocode, RISAFloor and RISA-3D used the full member length as the torque length when calculating torsional buckling. Now, per EN1993-1-1:2014 Section 13.3.2, we’ve added the...

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Detach an Integrated RISAConnection Model
October 3, 2017

Detach an Integrated RISAConnection Model

RISAFloor, RISA-3D, and Revit can export connection rule and loading information to streamline the design process for a project with numerous connections. This process helps to quickly create connections with the member shape, geometry, and loading information from the original program.

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Custom Loading in Integrated RISAConnection Model
September 15, 2017

Custom Loading in Integrated RISAConnection Model

RISAConnection v7.0.1 includes the option for customized loading in an integrated RISAConnection model. If you have used RISA-3D or RISAFloor to export connection rules for design in RISAConnection, they also exported over the forces per the solved load combinations.

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Enhanced Live Load Reduction
September 14, 2017

Enhanced Live Load Reduction

The consideration of Live Load reduction is a feature that has been in RISAFloor from the very beginning. However, recent changes to the interface make it significantly easier for you to understand how live load reduction is affecting the design forces in your structure.

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Vertical Slab and Beam Offsets
September 13, 2017

Vertical Slab and Beam Offsets

In RISAFoundation, you can add a vertical offset for slabs or beams. Traditionally, RISA uses centerline analysis which aligns all elements at their centerline. This is a common structural analysis assumption as the loads will get transferred to the centerline even if there is difference in the...

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Added Double Click Dialog for Members
September 12, 2017

Added Double Click Dialog for Members

RISAFloor now has the ability to double-click a member to open the Member Information dialog. This feature has been in RISA-3D but now it is available in RISAFloor. Double click any member in your model and the Member dialog box opens. It has three tabs: General, Properties and Design.

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