November 12, 2014

How do Unbraced Lengths affect Analysis?

The axial compression and flexure strength of beams and columns is dependent on the spacing of elements which provide bracing along the length of those members. You may specify unbraced lengths as a fixed distance or by using RISA’s Unbraced Length Commands. These unbraced lengths are used for member capacity calculations. However, specifying bracing via unbraced lengths does not provide physical bracing to the model for analysis. It only affects the member capacity calculated for code checks. See the example below.

For compression capacity, member M1 (above) is braced at N3 based on specified Lbyy and Lbzz.

However, for analysis this member is not considered braced (see above)

A bracing member (M2) must be modeled to provide bracing for analysis

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Tags: RISA-3D, RISAFloor, New, Unbraced Lengths

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…

March 3, 2021 | RISAFloor, New

Video: Using a DXF Underlay to Create Geometry in RISAFloor

Oftentimes the architecture of a building does not follow a simple rectangular nor radial grid. A quick and easy way to handle these scenarios within RISAFloor is to import the building geometry or grid system as a DXF underlay…

June 14, 2010 | RISA-3D, Plates, RISA-2D, New

How Do Plates Connect to Each Other?

To best understand how plates interact with each other you must first understand the concept of Physical Members. The important thing to keep in mind is that plates are not physical members. A plate is defined using either three or four joints, and it only connects to other plates at those joints. Plates do not connect to anything along their edges, or in their interior. See the example below: Node N4 falls along the edge of the bottom plate, and therefore it does not connect to the bottom plate. You should always avoid having a joint of any type fall along the edge, or in the interior of a plate. Usually submeshing can achieve this well, as shown below: Where a finer mesh is required in some parts of your model you can use trapezoidal plates to transition between the coarse and fine mesh. Notice how the mesh in the example below transitions to one twice as fine without any plate joints falling along the edge of other plates:…