
March 22, 2018
Utilizing RISA-3D for Seismic Design of Concrete Walls
In RISA-3D we now have the ability to design concrete shear walls for seismic forces.
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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In RISA-3D we now have the ability to design concrete shear walls for seismic forces.
You may now design a Brace to Column Base Plate Connection in RISAConnection v8. This connection type combines the original single column base plate with a gusset from a connected vertical brace member. The connection allows tapered or rectangular gussets that frame into either the column flange or...
In RISAConnection v8, you may now design a Knee Brace and Diagonal Brace with a tapered gusset plate. One of the greatest benefits is the decreased size of a brace gusset plate by manipulating the fold line location.
In RISA-3D we now have the ability to:
In RISA-3D, you can define a boundary condition as Fixed (reaction will be calculated) or Fixed, (reaction will NOT be calculated).
We are proud to introduce drastically improved solution times in RISAFoundation version 10.0. This version was updated to include multi-threading/parallel processing capability which will allow it to take advantage of multiple core processors which are becoming extremely common on the market today.
The BS EN 1992-1-1:2004+A1:2014 has been implemented in RISA-3D version 16.0 and RISAFloor version 12.0. To select this code for your design, simply open the Model Settings and under the Codes tab select BS EN 1992-1-1:2004+A1:2014 for concrete:
The new TMS 402-16 Masonry Code (formerly designated as ACI 530 and ASCE 5) have been added to RISA-3D v16.0, RISAFloor v12.0 and RISAFoundation v10.0.
An update to the Cold-Formed Steel Design Codes has been added to RISA-3D v16.0 and RISAFloor v12.0. Updated Codes include:
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