In this video, you’ll learn how to investigate your RISA-3D model for P-Delta divergence errors. This type of error is common in general structural analysis software and has two major causes: a model that is unstable or a model that is too flexible. For this investigation, two separate steel frame...
In a model that contains both RISAFloor and RISA-3D data it is possible to define your diaphragms as either flexible or rigid for lateral design. You can do this from the Diaphragms spreadsheet in either program:
Investigating P-Delta instabilities in RISA-3D (or RISA-2D) can be difficult. The first step is usually to solve the model without the P-Delta effect included to see if there are any obvious deflection problems that could cause issues with a P-Delta analysis. But, what can be done when this doesn’t...
Have you ever received an instability warning when running a three dimensional RISA-3D model? This is because RISA-3D cannot build the stiffness matrix with the configuration you have modeled. In some cases, your model is truly unstable and in others it’s a matter of correctly modeling your...
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.
When your RISA-3D model is not behaving as you anticipated, one of the best tools you have is viewing the deflected shape. Displaying the deflection graphically will help you visualize how the model is behaving and will often times bring to light modeling errors.
Before reading this, be sure to check out the article linked below on X-Bracing. In RISA-3D, you can set a member to be tension-only by selecting it and selecting Tension Only or Euler Buckling from the Additional Properties section of the Member Properties.
There are several tips to modeling X-Bracing within RISA-3D that can help the model solve faster and give you better results.
When it comes to trusses in RISA-3D, boundary condition definitions (pin vs. roller) can make a huge difference. Let’s take an example of a typical roof truss. Note that a pin-pin boundary condition has been applied to the ends.
