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FAQ 004193 EN

6 November 2019

Gerhard Rehm Results RFEM RSTAB

Why are imperfections taken into account in RFEM and RSTAB when calculating according to the linear static analysis, even though no component deformations are considered according to the linear static analysis?


In general, an imperfection describes the imperfection of a structure or the deviation due to its production from the ideal shape. There are different ways to simulate the imperfection. In RSTAB and RFEM, imperfections are represented as equivalent loads. The definition of equivalent loads is shown in Figure 01 and is taken from [1] . The same is described in EC3 [2] . Since these are equivalent loads that are dependent on the axial force, they are also taken into account for a calculation according to the linear static analysis. It is recommended to manage loads and imperfections in separate load cases. They can be suitably combined with each other in load combinations. For the load case general data (see Figure 02), load cases with pure imperfection loads have to be classified as the action type "Imperfection".


Imperfection 1st Order Theory Internal forces


[1]   Manual RFEM. (2018). Tiefenbach: Dlubal Software.
[2]   Eurocode 3: Design of steel structures - Part 1‑1: General rules and rules for buildings; EN 1993‑1‑1:2010‑12


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RFEM Main Program
RFEM 5.xx

Main Program

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

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RSTAB 8.xx

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The structural engineering software for design of frame, beam and truss structures, performing linear and nonlinear calculations of internal forces, deformations, and support reactions

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