The standards specify the relevant size and distributions that lead to efficient and reliable design checks. RF‑/FE‑LTB provides various settings for the standardization of a mode shape. We recommend graphically checking the imperfections applied in the calculation. You can display them in the Results Navigator.
Imperfections
Stability design according to the second-order analysis requires imperfections to be applied.
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The critical factor for lateral-torsional buckling or the critical buckling moment of a single-span beam will be compared according to different stability analysis methods.
There are two ways to specify eccentric nodal loads in RF-/FE-LTB. First, the nodal load has to be applied in the right direction. Then, you can assign either the resulting torsional moment or the eccentricity.
Stability design according to the second-order analysis requires imperfections to be applied.
The stability analysis of the steel frame described in my previous post can also be performed in RF‑/FE‑LTB according to the Equivalent Imperfection Method. This post describes how to calculate or determine the critical load factor.
In the "Edit Section" dialog box, you can display the buckling shapes of the Finite Strip Method (FSM) as a 3D graphic.
- Design of five types of seismic force-resisting systems (SFRS) includes Special Moment Frame (SMF), Intermediate Moment Frame (IMF), Ordinary Moment Frame (OMF), Ordinary Concentrically Braced Frame (OCBF), and Special Concentrically Braced Frame (SCBF)
- Ductility check of the width-to thickness ratios for webs and flanges
- Calculation of the required strength and stiffness for stability bracing of beams
- Calculation of the maximum spacing for stability bracing of beams
- Calculation of the required strength at hinge locations for stability bracing of beams
- Calculation of the column required strength with the option to neglect all bending moments, shear, and torsion for overstrength limit state
- Design check of column and brace slenderness ratios
The seismic design result is categorized into two sections: member requirements and connection requirements.
The "Seismic Requirements" include the Required Flexural Strength and the Required Shear Strength of the beam-to-column connection for moment frames. They are listed in the ‘Moment Frame Connection by Member’ tab. For braced frames, the Required Connection Tensile Strength and the Required Connection Compressive Strength of the brace are listed in the ‘Brace Connection by Member’ tab.
The program provides the performed design checks in tables. The design check details clearly display the formulas and references to the standard.
In the Concrete Design provides an option to perform seismic design according to AISC 341-16 for steel members.
Five SFRS types (Seismic Force-Resisting Systems) are available for this.
More Information
What are the options in RFEM 5 or RSTAB 8 for determining the ideal elastic critical moment for lateral-torsional buckling for any cross-sections and systems/loads? Is it also possible to design flat steel (brackets, flat steel stringers of staircases)?
I am using the FE‑LTB program to design a hall frame.However, not all internal forces are transferred when importing the loads from RSTAB. Why not?
In the RF‑/LTB add-on module, I can only select load cases and load combinations for design. Why can I not also select result combinations?
How do I define a plastic hinge in RFEM 6?
How can I exchange data between RFEM 6 / RSTAB 9 and IDEA StatiCa?
How can I generate an area load on members via cells in RFEM 6 or RSTAB 9?
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