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February 15, 2011
What is the Difference Between a Boundary Condition and an End…
In RISA-3D, there are numerous options for Member End Releases which should not be confused with Boundary Conditions.
If you've ever wondered what it’s like to be an industrial structural engineer, let me paint you a picture: Imagine juggling a dozen problems at once—steel frames, conveyor supports, pipe racks, tank foundations—all while trying to decipher a set of drawings that look like they were faxed from 1997. And, of course, every single solution is needed yesterday. But don’t worry! With the right tools (cough RISA and ADAPT cough), navigating this daily chaos becomes a lot more manageable. So, grab your coffee (black, obviously), and let’s walk through a typical day. 6:30 AM: Morning Coffee & Evaluating Additional Loads The first email of the day: “Can we add another 10,000 lbs of equipment to the mezzanine? What about seismic drift and vibration?” Instead of a lengthy hand calculation, you fire up RISAFloor and check gravity load distribution. Exporting to RISA-3D, you analyze modal frequencies and check if the additional weight will push the structure into an uncomfortable range for human occupancy. Seismic drift is next. A quick response spectrum analysis in RISA-3D confirms that the drift is still within acceptable limits. You send your report with confidence—no major framing changes required. 9:00 AM: Field Issue - Pipe Rack Base…
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In RISA-3D, there are numerous options for Member End Releases which should not be confused with Boundary Conditions.
To understand decks it is important to know what a deck is. In typical buildings, most of each floor will consist of only one type of deck.
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 a model is loaded, it deflects. The deflections in the members of the model may induce secondary moments due to the fact that the ends of the member may no longer be vertical in the deflected position. These secondary effects for members can be accurately approximated through the use of...
Continuous tiedown systems are used to help resist overturning forces generated by lateral loads, and can be estimated in RISA-3D using the hold-down database and the strap forces.
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.
When you have a plate model for a slab or wall in RISA-3D, the Internal Force Summation Tool (IFST) is a very useful analysis tool to get exactly the forces that you want to design for. To use the tool, you must:
When using rigid diaphragm analysis in RISA-3D it can be useful to evaluate the story shear in each frame. This is a perfect application for the Internal Force Summation Tool. The first step is to solve the desired load combination.
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