March 17, 2010

Do You Ever Get the “LOCKED” Message on a Simple Beam Model?

By: RISA

Do you get an instabilities warning when you’re trying to do a simple 2D model in RISA-3D?

Below is the easiest way to test and fix the instability:

Open the Node Reactions spreadsheet, and see which joint is unstable.

In the Boundary Conditions spreadsheet, apply a Reaction to the joint in the degree of freedom that was LOCKED.

Re-run the model and examine the Node Reactions.

If the reaction that is restraining the instability is showing a ZERO force or moment, then the instability is inconsequential to the results. Also, if the reaction that is restraining the instability is showing a non-zero force or moment, then you have a problem with the model that must be corrected for you to get valid results.

Tags: RISA-3D, New, Instability

June 19, 2014 | RISA-3D, Loads, New

How to Use Moving Loads

RISA-3D and RISA-2D will allow you to add a moving load pattern to your model and include it in your envelope solution. 1. Adding a New Moving Load Pattern To learn about adding new moving load patterns to your Moving Load Patterns library, please see the How Can I Add a New Pattern to the Moving Load Database blog. 2. Defining the Moving Load Path Once you have added your moving load pattern, you can apply it to your model in the Moving Loads spreadsheet (Spreadsheet > Loads > Moving Loads). In this spreadsheet, you will define the following: Tag: Label of the moving load (this cannot be changed). Pattern: Select the moving load pattern from the dropdown menu. This menu reads in all the patterns that are listed in your moving load library (Advanced > Moving Loads). Increment: Specify the distance at which the load will be stepped through the path. Both Ways: If you want the load pattern to reverse once it has reached the final node along the path, check this box. Node Entries: These define the path of the moving load. Note: You may skip intermediate points along a straight line when specifying the path. 3…

March 1, 2012 | RISA-3D, RISAFloor, RISA-2D, New, RISASection

How to Get a Code Check for Custom Cold Formed Steel Shapes

In order to get code calculations, RISA-3D and RISA-2D need to know what type of shape would be most similar to yours. This is because the program needs to use the correct code equations for your shape type. You can easily add your custom shape to the Cold Formed library of shapes. First, pick a similar shape type (Channel, Hat, Zee, etc.) and then add the section properties into the Shape Database. You can calculate the section properties manually or use RISASection to calculate the section properties for you. Step 1: Select a similar shape type. Step 2: Click Add to create new section. Step 3: Create a name and add section properties to the start shape. Then, click OK. Note: This step is the first attempt at creating the shape and the section properties do not need to be exact just yet Step 4: Select the new shape and click Edit. Now you can enter in all the section proprieties from your hand calculations or the RISASection calculations…

May 10, 2011 | RISA-3D, New, Instability

Are You Receiving Instability Warnings for Your Truss Model in…

When running a truss model in RISA-3D or RISA-2D, it’s quite common to receive an instability warning, but these can be easily resolved by following a few simple rules. Rule #1: Every joint in your model needs to have at least one member with a fixed end release. In trusses, it’s typical to have all members with pinned end releases so be sure to change the end releases to comply with this rule. Rule #2: Brace the truss so it doesn’t “flop” out of plane. You can do this by creating an additional boundary condition to brace all of the joints for any out of plane motion. Assuming the truss is in the XY plane, below is the boundary condition you can add:…