
October 4, 2012
Using Virtual Joist Girders in RISA-3D
The Steel Joist Institute (SJI) has developed a Virtual Joist Girder table which converts common joist sizes into equivalent wide flange beams for use in RISA-3D.
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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The Steel Joist Institute (SJI) has developed a Virtual Joist Girder table which converts common joist sizes into equivalent wide flange beams for use in RISA-3D.
Let’s consider the example of the frame shown below. Suppose there is a diaphragm present at the framing level, and that the wall shown is intended only to handle the lateral loads. In reality the columns will be in-line with the wall, and the cantilever beams will pass over the wall without...
RISA programs are Windows-based and require a Windows operating system to run. Although RISA software does not operate natively on macOS, it is compatible with virtual machines that run Windows OS on your Mac. Below are the steps to get RISA up and running smoothly:
RISAFoundation includes a footing element which is represented by a single node. A frequent question that arises is how to apply multiple point loads to a single footing, but at different locations. This can be done with or without corresponding pedestals, but for the example below multiple...
While RISA-3D does not currently have pilaster design, there are still plenty of situations where you would want to have a column embedded within a wall. The idea behind this is that the column handles the gravity loads for any beams which frame into it, while the wall handles lateral loads. No...
RISAFloor has some default decks provided for you when you open the program in the Deck Definitions spreadsheet. You can use one of these decks or you can create your own by going to the bottom of the spreadsheet and press ENTER.
RISA-3D v10 now has the ability to quickly and easily apply hydrostatic loads to circular tanks using the Cylinder Generator. This generator can be found by clicking the Templates button and choosing the Cylinder - Plates/Members option.
With the new RISAConnection version 2.0, users now have the ability to design all connections for axial forces as well as the shear and moment forces.
RISA-3D now has the ability to design concrete walls with openings for both in-plane and out of plane loading. For lintels we provide analysis results based on the finite element results of the region above the opening.
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