A video showing the different results calculated for LTB between an Eigenvalue analysis and Chapter F from the AISC.
KB 001679 | AISC Chapter F Lateral Torsional Buckling Versus Eigenvalue Calculation Methods Compared
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![Steel Beam](/en/webimage/013895/2796237/2020-11-04_16-36-41.png?mw=512&hash=4639c92dc4bb2b8364042a2f706fc23743a50b1e)
Utilizing the RF-STEEL AISC add-on module, steel member design is possible according to the AISC 360-16 standard. The following article will compare the results between calculating lateral torsional buckling according to Chapter F and Eigenvalue Analysis.
![Warping Restraint via End Plate](/en/webimage/010484/2978100/1_warping_restraint_from_end_plate.png?mw=512&hash=b43e17cbb11faa3b51820d5bc88f6c5f2d58db81)
In the case of open cross-sections, the torsional load is removed mainly via secondary torsion, since the St. Venant torsional stiffness is low compared to the warping stiffness. Therefore, warping stiffeners in the cross-section are particularly interesting for the lateral-torsional buckling analysis, as they can significantly reduce the rotation. For this, end plates or welded stiffeners and sections are suitable.
![Entering Intermediate Lateral Restraint in Center of Member 1](/en/webimage/010537/2968407/1_Intermediate_lateral_restraint_in_the_middle_of_beam_1.png?mw=512&hash=b59e15e6f9f5b251a280addda3968092369a2f14)
The support conditions of a beam subjected to bending are essential for its resistance to lateral-torsional buckling. If, for example, a single-span beam is held laterally in the middle of the span, the deflection of the compressed flange can be prevented, and a two-wave eigenmode can be enforced. The critical lateral-torsional buckling moment is increased significantly by this additional measure. In the add-on modules for member design, different types of lateral supports on a member can be defined using the "Intermediate supports" input window.
![W10X66 User-Defined Column](/en/webimage/014874/2959540/001638.png?mw=512&hash=b566bc647a3dc21b0428c3b3779c061e683a67a3)
Sometimes a structure needs reinforcement in cases where a new floor is being added, or when an existing member is found to be under design due to a hard-to-predict loading assumption. In many cases, the structural member may not be easily replaced, and reinforcement is implemented to meet the new loading requirement.
![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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