In EN 1993-1-1, the General Method was introduced as a design format for stability designs, which can be used for planar systems with any boundary conditions and variable structural height. The design checks can be performed for loading in the main load-bearing plane and simultaneous compression. The stability cases of lateral-torsional buckling and flexural buckling are analyzed from the main supporting plane, that is, about the structural component's weak axis. Therefore, the question often arises how to design in this context flexural buckling in the main load-bearing plane.
KB 000868 | General Method for Stability Analyses According to EN 1993-1-1 and Buckling in...
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In EN 1993-1-1, the General Method was introduced as a design format for stability analyses that can be applied to planar systems with arbitrary boundary conditions and variable structural height. The design checks can be performed for loading in the main load-bearing plane and simultaneous compression. The stability cases of lateral-torsional buckling and flexural buckling are analyzed from the main supporting plane; that is, about the weak component axis. Therefore, the issue often arises as to how to design, in this context, flexural buckling in the main load-bearing plane.
The following article describes the design of a single-span beam subjected to bending and compression, which is performed according to EN 1993‑1‑1 in the RF-/STEEL EC3 add-on module. Since the beam is modeled with a tapered cross-section and thus it is not a uniform structural component, the design must be performed either according to General Method in compliance with Sect. 6.3.4 of EN 1993‑1‑1, or according to the second-order analysis. Both options will be explained and compared, and for the calculation according to the second-order analysis, there is an additional design format using Partial Internal Forces Method (PIFM) available. Therefore, the design is divided into three steps: design according to Sect. 6.3.4 of EN 1993‑1‑1 (General Method), design according to the second‑order analysis, elastic (warping torsion analysis), design according to the second‑order analysis, plastic (warping torsion analysis and Partial Internal Forces Method).
The following structure is covered as Example IV.10 in [1] "Comment on Eurocode 3". For a support with a linearly varying cross‑section, a sufficient ultimate limit state design (cross‑section check and stability analysis) is to be performed. Due to the unequal structural component, it is necessary to perform the stability analysis (from the main support direction) using the method according to Section 6.3.4, or alternatively, according to the second‑order analysis.
For the stability design of members and sets of members with a uniform cross-section, you can use the equivalent member method according to EN 1993-1-1, 6.3.1 to 6.3.3. However, as soon as a tapered cross-section is available, this method can no longer be used, or only used to a limited extent. The RF-/STEEL EC3 add-on module can automatically recognize these cases and switch to the general method.
In the ultimate configuration of the steel joint design, you have the option to modify the limit plastic strain for welds.
Using the "Base Plate" component, you can design base plate connections with cast-in anchors. In addition to plates and welds, the design analyzes the anchorage and the steel-concrete interaction.
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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