For the selection, the load reference is crucial. When entering the torsional moment, the load acts independently of the deformation. In detail, this means that the load remains constant when rotating the member around its axis. The more common case of dividing the load by the rotation is created using the defined eccentricity. For example, if there is an eccentricity for a load in the local z‑direction, the member torsion causes the resulting torsional moment to be partially redistributed in the local y‑direction, so the torsional moment failure is smaller than in the first case.
Eccentric Nodal Loads
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.
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![System and Loading](/en/webimage/008936/577926/01-en.png?mw=512&hash=65e98cfe859ce35a3e3e9da47a0ef9335401520e)
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.
![Eccentric Nodal Loads in RF-/FE-LTB](/en/webimage/009883/2420951/01-en-png-png.png?mw=512&hash=6ca63b32e8ca5da057de21c4f204d41103e6fe20)
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.
![Imperfections](/en/webimage/009948/2421508/01-en-png-png.png?mw=512&hash=6ca63b32e8ca5da057de21c4f204d41103e6fe20)
Stability design according to the second-order analysis requires imperfections to be applied.
![Critical Load Factor of Tapered Steel Frame 2: Calculation in RF-/FE-LTB](/en/webimage/010007/2422008/01-en-png-9-png.png?mw=512&hash=5737f44b31a0883cd584e5e0da784bf91a036347)
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.
![Add-on "Steel Joints for RFEM 6" | Component Library](/en/webimage/043097/3898884/steel_joints_components.png?mw=512&hash=e4f835906155863fc7019d5043b22e553dc766f9)
- Numerous component types, such as base and end plates, web angles, fin plates, gusset plates, stiffeners, tapers, or ribs for easy input of typical connection situations
- Universally applicable basic components (such as plates, welds, bolts, auxiliary planes) for modeling complex connection situations
- Graphical display of the connection geometry with dynamic updating during the input
- Wide range of cross-section shapes: I-sections, U-sections, angles, T-sections, hollow sections, built-up cross-sections and thin-walled sections
- Library in the Dlubal Center with a large number of program-side template connections, including user-defined templates
- Automatic adaptation of the connection geometry based on the relative arrangement of the components to each other – even in case of subsequent editing of the structural components
![Feature 002820 | Limit Plastic Strain for Welds](/en/webimage/050344/3881226/1.png?mw=512&hash=9d7f6c198b6d4ae6ee8f2fa8bca75f85579e14c9)
In the ultimate configuration of the steel joint design, you have the option to modify the limit plastic strain for welds.
![Component "Base Plate"](/en/webimage/050345/3936120/50345.png?mw=512&hash=3bd641cb1a2445804b338855e4debfc40c6563e9)
The "Base Plate" component allows you to design base plate connections with cast-in anchors. In this case, plates, welds, anchorages, and steel-concrete interaction are analyzed.
![Feature 002807 | 3D Display of FSM Results](/en/webimage/049281/3861162/2024-05-01_10-32-55.png?mw=512&hash=2377d291bc20ac3d78d617b50c131614e99ac6f7)
In the "Edit Section" dialog box, you can display the buckling shapes of the Finite Strip Method (FSM) as a 3D graphic.
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