Problems:
To perform steel design check, the following issues exist.
Assigning the design type 'boundary condition': it only allows me to defined lateral design supports at the nodes. I cannot define continuous lateral support.
a continuous lateral restraint can be defined using a member shear panel. For this purpose, the corresponding member or member set must be assigned an appropriate member support.
Whether the member support should be assigned to the member or the member set depends on which object is being designed in the Design Add-On:
If a member is designed, the member support must be assigned to this member.
If a member set is designed, the member support must be assigned to the member set.
Procedure
Assign a fictitious stiffness of type “Shear Panel” to the member support (see Image 1).
In the “Shear Panel” tab, you can create a new shear panel type or select an existing one (see Image 2).
Various shear panel types are available in the list. You can also define the stiffness manually using the type Define S-prov (see Image 3).
Important Notes
This fictitious stiffness has no effect by default on the static, stability, or modal analysis.
The shear panel is considered only when determining the elastic critical moment or the critical load factor for lateral-torsional buckling if this is determined by the internal eigenvalue solver.
I defined the s-prov shear panel in y-direction. But I am still getting too high design ratio for lateral buckling. Why is this design check even being applied to this member if it is continuously supported?
Also, why is it so that flipping the direction of the members inside the member set, which visually also flips the side on which the graphical representation of the member support is shown, changes the results. Although in the definition of the member support there is no lateral directionality, and I have defined the member support support eccentricity to be at the center of the cross-section?
In the chosen verification method, which is based on the general approach adopted from Johannes Naumes, both lateral-torsional buckling and flexural buckling are evaluated within one combined check.
For reference, the method is described in:
Johannes Naumes, Markus Feldmann & Gerhard Sedlacek Biegeknicken und Biegedrillknicken von Stäben auf einheitlicher Grundlage,
Band 70, Shaker Verlag, 2010.
Possible reason for differing design check ratios
The differing design check ratios may be caused by the loads being defined in the local axes.
If these axes are reversed, the internal forces can change because the loads or imperfections act in different directions.
Please double-check the internal forces to ensure they are consistent with your expectations.
Still uncertain?
If this does not answer your question, feel free to send the relevant file to us, either by uploading the file here or by sending it to me me via direct message.
The stability analysis according to Naumes is always performed for compression and/or bending.
In your model, the reduction factor χop for buckling or lateral-torsional buckling is 1.0, meaning no reduction is applied (see Figure 1).
If you do not want to perform a stability check for a specific member or member set, simply assign a design configuration to that member or member set in which the stability check is deactivated (see Figure 2).
Yes, assigning a new design configuration without stability check is what I ended up doing for those laterally supported beams, out of desperation.
I think it is not logical to perform stability analysis using the Naumes method for members that are continuously laterally supported and give larger-than-one design ratio which is a not realistic.
I hope this feature is implemented in the future so that users wouldn't have to go through this rabbit hole as I went and end up resorting to a band-aid fix such as manually forcing the software not to perform stability analysis for continuously laterally supported beams.
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Please double-check the internal forces to ensure they are consistent with your expectations.
