Modeling Stacked Beams
Rigid Links to the Rescue

Here is a very simple and perhaps common building technique that turns out to be rather tricky to model with a finite element program like VisualAnalysis 5.5. Thanks to Ken Gaston from Bellingham WA, who posed this little challenge to IES technical support.

The Problem

Say you have a beam running east-west, now you stack on top of that a beam running north-south. The two are simply connected, yet they are both continuous bending elements and the top beam only transfers shear to the lower beam--no bending moment or twisting moments. How should you model it?

A Solution

One possible solution involves using a rigid-link element to model the connection. (This is similar to the scissors-joint technique described in our FAQ.) Model your beams at different elevations. Split the members where they would cross if they were at the same elevation. (They will automatically be modeled as Combined Members in VisualAnalysis 5.5.) Then connect them with a short rigid link. The rigid link should be relatively stiff, and the moments at one end should be released to prevent moment transfer between your two "real" beam elements.

Watch Out for Instabilities

When introducing rigid links into your model, you will need to be careful to include enough supports or to minimize extra end-releases to avoid instability problems. For example, the beam elements will not be restrained against any torsion at the intersection points, so you may need to include a torsional restraint at one end of the beam. This is true even if the beams are not loaded in a way that would cause torsion. You need to take care of the mathematical instabilities that could arise in the stiffness equations.

A Complete Example Project

If you would like to see this solution in a complete model in VisualAnalysis 5.5 (this file will not open in prior versions), you may download and unzip this: stacked-beams.zip

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Back to School Blobs
Terry Succumbs to Academic Pressure

I (Terry) was taken to task by the professors this Fall when I tried to give schools an 'upgrade' from VisualAnalysis 4. It seems that those in the Ivory Towers just cannot teach students how to design buildings without resorting to members that look like, well, we can't show you a picture because they don't really have a shape! Perhaps this picture will help:

Those of us who model real-world structures (or at least do so vicariously through real-world engineers) usually build models using W shapes in steel, rectangles in wood or concrete, and the like. IES accordingly offers a large database of manufactured shapes.

The Proper IES Method

We also provide a great utility program in ShapeBuilder to construct cross-sections and calculate geometric and structural properties of other, more complicated or less popular shapes. This tool helps you create a shape and save it in the IES database for use on future projects. Shapes you create in ShapeBuilder will actually render correctly in the VisualAnalysis Picture View and, if defined completely, can in many instances work in VisualDesign as well.

There is also the Shape Database Editor, included with ShapeBuilder, that allows you to create custom shapes without actually defining the shape, or for importing entire libraries of foreign shapes. You can even share your slick new database with the engineers down the hall (assuming they have purchased a license to use IES software).

Uncle! Uncle!

It turns out, though, that I was wrong. I admit it. It took me three years, and lots of discussions with many engineers and staff members at IES. Philosophically, I am still very much opposed to indistinct shapeless forms. But frankly, I'm just plum tired of trying to defend the position. You really do need the feature, please forgive me for removing it!

Rebirth of a Feature

In repentance, I have re-introduced, the "User-Defined Shape", or the "Custom Shape" feature, in a slightly different form into VisualAnalysis 5.5 Package (Build 7). Because these are indistinct shapeless forms, they are dubbed "Custom Blobs".

Blob Feature Details

In this initial release you may create blobs, give them a name and properties, and re-use them for other members in the same project. Shear-area properties are only available in the 'Advanced' level of VisualAnalysis. Blobs are saved with the project file, but are not available to other projects. Once created, you cannot edit them, but of course if you get it wrong you can easily create more and more blobs.

If the blob shape is not used by any members, it will automatically be removed when the file is closed and reopened. In a Picture View they will display as a rectangle or square proportional to the properties you have defined--watch out for HUGE properties!

What a Grumpy Old Man...

Go ahead and model the whole world with BLOBS if you like! Just don't tell me about it. If I start having to do technical support for Blobs, you may get some indistinct shapeless answers!! I won't be holding my breath waiting for photos of all the blob-based structures you will be constructing either.

It sure is a good thing students are still somewhat teachable once they graduate.

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Masonry Design Software

Walls, Lintels, Pilasters, Shear Walls, Beams & Columns!

When we asked you last Fall what you wanted from IES, the answer was clear: Masonry Design. IES has a new tool coming soon that stacks up well in our current product lineup, and will act like grout in the cracks between our other tools.

The forthcoming QuickMasonry follows MSJC requirements to provide easy design checks and organization for all of the masonry components in your structures. With the same kind of clarity and quality as our other Quick products, the new tool will be immediately familiar to many.

The QuickMasonry product will be available in the fourth quarter of this year. The product will be entering "beta testing" shortly. We have not yet set pricing on this product or made it available for pre-ordering. Watch for further updates in October or early November.

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