In the first step, the iteration process uses an arbitrary start value for the unknown variable and solves the terms on the left and the right side of the equation. If the equation is not fulfilled, the process repeats with a modified start value. This iterative process continues until the equation is fulfilled. In this case, we talk about convergence and the last used variable value is the solution.
The accuracy of this procedure depends on the variables used. This means that it is usually necessary to perform a lot of iteration steps to find the exact solution. If a solution with the reduced accuracy is sufficient, the convergence of the iteration is related to a tolerance criterion. In this case, a new iteration is only started if the difference between the terms of the left and the right side of the equation is greater than the defined tolerance criterion.
Iterative Processes in Structural Analysis
- Determination of internal forces on a deformed system (second-order analysis)
- Simulation of nonlinear material properties (plasticity)
- Determination of contact stresses between two bodies positively connected to each other
Iteration in RFEM and RSTAB
In RFEM and RSTAB, the criteria and maximum iterations for nonlinear calculations are organized under "Calculation" → "Calculation Parameters" in the "Global Calculation Parameters" tab.
Calculation and Design of Two-Story Building: Analysis of Two Options (Steel-Concrete Composite Structure and Modular Construction)
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.
- When calculating a cable using the STEEL EC3 add‑on module, he error message "Incorrect characteristic stresses for material No. 1! Please correct this in Table 1.2." appears.
- Are the effective length coefficients in the add-on modules for the aluminum and steel design automatically determined from the model or do I have to make adjustments?
- I design a cross-section created in the SHAPE‑THIN program by using the RF‑STEEL EC3 add-on module, but the program shows the error message "ER006 Invalid type of c/t-part for cross-section of type General." What can I do?
Is it possible to calculate American steel cross-sections?
- Where do I find the setting to specify the entered structural component as a "wall" or "slab"?
- How can I quickly model a chimney with reinforcement rings and stiffeners?
- How can I model and design general bolted connections with the surface and solid elements in RFEM?
- I get the message "Existing torsion -> no stability design possible." Why does this appear and what can I do?
- I design an asymmetric cross-section and get the message: "Non-designable: ER051) Moment about z‑axis on asymmetric cross-section, taper or set of members." Why?
- How can I consider holes in steel members?
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
The structural engineering software for design of frame, beam and truss structures, performing linear and nonlinear calculations of internal forces, deformations, and support reactions