
May 1, 2020
Video: Wood Member Design in RISACalc
Learn how to load and design individual beam and column wood members in RISACalc.
Rigid diaphragms in RISA-3D are a powerful way to model how floor systems distribute lateral loads. By forcing all connected nodes to move together in-plane, they effectively capture the stiffness of a concrete slab or diaphragm deck—often simplifying analysis without sacrificing accuracy. However, when rigid diaphragms are combined with sloping members, they can introduce unexpected behavior that changes how the structure resists loads—sometimes creating a hidden “tension tie” that doesn’t exist in the real system. When Rigid Diaphragms Alter the Model’s Behavior Consider a simple moment frame with sloped beams under gravity loads—common in pre-engineered metal buildings. Model 1: No rigid diaphragm applied Model 2: Identical frame, but with a rigid diaphragm located at the eaves When reviewing the strong-axis bending moments, column base reactions, and thrust forces: The first frame behaves as expected. The second frame (with the rigid diaphragm) shows reduced bending moments and smaller thrust reactions at the column bases. At first glance, this might seem like an improvement—but it’s actually unrealistic behavior caused by the diaphragm. Why It Happens: The “Hidden Tension Tie” In the model with the rigid diaphragm, the diaphragm prevents the eaves from moving apart under load. This effectively turns the diaphragm into…
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Learn how to load and design individual beam and column wood members in RISACalc.
RISAFloor supports the use of flexible diaphragms on both flat and sloped roofs. Before reviewing the workflow for utilizing a flexible diaphragm on a sloped roof, it makes sense to review and understand the basic behavior of flexible diaphragms within RISAFloor. To do this, please first review the...
Over the last few weeks, we have been working hard to add the features and functionality that our customers have requested as well fix some of the issues that have been reported. With that in mind, we have prepared a new update of RISA-3D (v18.0.4) that includes the following features as well as...
When designing concrete shear walls for lateral loading, RISA-3D includes design checks for both in-plane and out-of-plane shear. In the condition where a concrete wall is under both axial tension and out-of-plane shear, the out-of-plane shear limit state for a specific region within the concrete...
With many of us working from home, our support team wanted to be able to connect with our customers where they are: in front of their computers. With that in mind, we are excited to introduce RISA Live. These live sessions, will take place every Thursday at 2pm EST (11am PST) and will focus on...
In RISA-3D when drawing members you must start with initial sizes. After loading and load combinations are completed the model is solved and then member design must be done, making sure that members pass for both strength and serviceability considerations. For both strength and serviceability...
RISA-3D allows users to import dxf files directly from software like AutoCAD, Microstation and ArchiCAD. Upon import, the files can be used either as a dxf underlay, giving the user the ability to trace complex geometry in RISA-3D or as a direct import in order to convert members and plates into...
RISA-3D includes the ability to design steel structures for seismic provisions found in AISC 341 and AISC 358 including moment frames and braced frames. For more information, review the video below.
Over the last few weeks, we have been working hard to add the features and functionality that our customers have requested as well fix some of the issues that have been reported. With that in mind, we have prepared a new update of RISA-3D (v18.0.3) that includes the following features as well as...
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