Rib Pattern

Lateral-Torsional Buckling (LTB) is a phenomenon that occurs when a beam or structural member is subjected to bending and the compression flange is not sufficiently supported laterally. This leads to a combination of lateral displacement and twisting. It is a critical consideration in the design of structural elements, especially in slender beams and girders.

RFEM 6 offers the Aluminum Design add-on for the design of aluminum members. This article shows how Class 4 sections are designed according to Eurocode 9 in the program.

This article discusses the options available for determining the nominal flexural strength, M_nlb for the limit state of local buckling when designing according to the 2020 Aluminum Design Manual.

You know for sure that when connecting tension-loaded components with bolted connections, you need to consider the cross-section reduction due to the bolt holes in the ultimate limit state design. The structural analysis programs also have a solution for this. In the Aluminum Design add-on, you can enter a member local section reduction for this. Enter the reduction of the cross-section as an absolute value or as a percentage of the total area at all relevant locations.

• Calculation of deflections and comparison with the normative or manually adjusted limit values
• Consideration of a precamber for the deflection analysis
• Different limit values are possible, depending on the design situation type
• Manual Adjustment of Reference Lengths and Segmentation by Direction
• Calculation of deflections related to the initial structure or to the deformed structure
• Further detailed design checks depending on the selected design standard (for example, vibration design according to EN 1999‑1‑1, 7.2.3)
• Graphical result display integrated in RFEM/RSTAB; for example, the design ratio of a limit value, or the deformation or the sag
• Complete integration of the results into the RFEM/RSTAB printout report

The program does a lot of work for you. For example, the load or result combinations required for the serviceability limit state are generated and calculated in RFEM/RSTAB. You can select these design situations for the deflection analysis in the Aluminum Design add-on. Depending on the specified precamber and reference system, the program determines the deformation values at each location of a member. They are then compared to the limit values.

You can specify the deformation limit value individually for each structural component in Serviceability Configuration. In this case, you define the maximum deformation depending on the reference length as the allowable limit value. By defining design supports, you can segment the components. In this way, you can determine the corresponding reference length automatically for each design direction.

And that's not all. Based on the position of the assigned design supports, the program allows you to automatically determine the distinction between beams and cantilevers. The limit value is thus determined accordingly.