Manual adjustment of the buckling curve according to EN 1993-1-1
Tips & Tricks
The RF-/STEEL EC3 add-on module automatically transfers the buckling line to be used for the flexural buckling analysis for a cross-section from the cross-section properties. In particular for general cross -sections, but also for special cases, the assignment of the buckling line can be adjusted manually in the module input.
Flexural buckling curves according to EN 1993-1-1, Table 6.2
The buckling lines in the standard indicate the reduction factor χ to be used depending on the related slenderness ratio λ ̅. This reduction of the load -bearing capacity takes into account the influence of the geometric and structural imperfections on the component stiffness. These are included in the calculation formula of the reduction factor via an imperfection factor α.
The most favorable buckling line a0 represents the least influence of the imperfections and thus provides a higher flexural buckling resistance with the same slenderness. The most unfavorable buckling curve with the largest imperfection factor is buckling curve d.
|Imperfection coefficients according to EN 1993-1-1, Table 6.1|
|buckling curve||a0||Image 02 - Selection of the buckling line in the RF-/STEEL EC3 add-on module||b||c||d|
|Imperfection Factor α||0.13||0.21||0.34||0.49||0.76|
Manual adjustment in RF-/STEEL EC3
In the input window of the cross -sections, the cross -section details are displayed again in the add -on module. For each cross -section, you can select the buckling curve differently from the database value in the detail settings.
Dipl.-Ing. Oliver Müller
Product Engineering & Customer Support
Mr. Müller is responsible for the development of the add-on modules for steel structures and provides technical support for our customers.
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SHAPE-THIN determines the effective cross-sections according to EN 1993-1-3 and EN 1993-1-5 for cold-formed sections. You can optionally check the geometric conditions for the applicability of the standard specified in EN 1993‑1‑3, Section 5.2.
The effects of local plate buckling are considered according to the method of reduced widths and the possible buckling of stiffeners (instability) is considered for stiffened sections according to EN 1993-1-3, Section 5.5.
As an option, you can perform an iterative calculation to optimize the effective cross-section.
You can display the effective cross-sections graphically.
Read more about designing cold-formed sections with SHAPE-THIN and RF-/STEEL Cold-Formed Sections in this technical article: Design of a Thin-Walled, Cold-Formed C-Section According to EN 1993-1-3.
- I perform a stability analysis of a beam for lateral-torsional buckling. Why is the modified reduction factor χLT,mod used in the design according to DIN EN 1993‑1‑1, 6.3.3 Method 2? Is it possible to deactivate this?
- I need to define different types of lateral intermediate restrains for a single element in RF-/STEEL EC3. Is this possible?
- I compare the flexural buckling design according to the equivalent member method and the internal forces according to the linear static analysis with the stress calculation according to the second-order analysis including imperfections. The differences are very large. What is the reason?
- Why are the equivalent member designs grayed out in the Stability tab when activating the plastic designs by using the partial internal force method (RF‑/STEEL Plasticity)?
I design a set of members by using the equivalent member method in RF‑/STEEL EC3, but the calculation fails. The system is unstable, delivering the message "Non-designable - ER055) Zero value of the critical moment on the segment."
What could be the reason?
- I cannot see any members if the RF-/STEEL EC3 add-on module is selected as a "load case," why?
- To which axes refer the support rotations and support eccentricities in RF‑/STEEL EC3 Warping Torsion?
- What does the load application point in RF-/STEEL EC3 Warping Torsion refer to?
- Why do I get different design results for a load combination (CO) and a result combination (RC) in STEEL EC3 in spite of the same internal forces?
When designing a beam, I would like to neglect the torsion included in the stability analyses using the filters described in Knowledge Base Article #001498.
I define the filter, but the torsion warning appears at the same x‑location again. Do the design internal forces change, or why is that?
Structural engineering software for finite element analysis (FEA) of planar and spatial structural systems consisting of plates, walls, shells, members (beams), solids and contact elements
Design of steel members according to Eurocode 3
The structural engineering software for design of frame, beam and truss structures, performing linear and nonlinear calculations of internal forces, deformations, and support reactions
Design of steel members according to Eurocode 3