Why Don’t My Response Spectra Reactions Satisfy Statics?
April 3, 2012

Why Don’t My Response Spectra Reactions Satisfy Statics?

The applied loads in a response spectrum analysis (RSA) are the applied masses times the accelerations in the response spectra. Each mode of vibration produces its own set of joint reactions. The reactions for each mode obey statics as shown in the portal frame example shown below: Response...

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How Do I Resolve a P-Delta Instability?
February 23, 2012

How Do I Resolve a P-Delta Instability?

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...

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RISA-2D Educational Version
November 19, 2011

RISA-2D Educational Version

Students and Professors can utilize a special version of RISA-2D which is aimed at teaching and understanding the basics of structural analysis. While this version has a limited number of features, it will prove to be a useful tool in expanding the students structural engineering knowledge.

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Using Projected Loads in RISA-3D
August 18, 2011

Using Projected Loads in RISA-3D

RISA-3D, RISA-2D and RISAFloor have the capability to project distributed and area loads onto members. Consider the case of snow load on two buildings: one with a flat roof and one with a sloped roof. Ignoring the concept of shedding, if both buildings have the same footprint then they should both...

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How to Model a Hole in a Plate
June 16, 2011

How to Model a Hole in a Plate

While RISA-3D (or RISA-2D) does not have an explicit tool to punch a hole in a plate, you can use the following steps to manually model them:

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How RISA-3D Handles Single Angles
March 31, 2011

How RISA-3D Handles Single Angles

The bending and axial code checks for single angles differ somewhat from other shape types, because single angles behave quite differently in bending and compression depending on how they are braced along their length.

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How Do I Investigate My RISA-3D Model Using the Deflected Shape?
March 9, 2011

How Do I Investigate My RISA-3D Model Using the Deflected Shape?

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.

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