Generally, RF-LTB performs the analysis according to the equivalent member method described in DIN 18800, part 2. A separate dialog box allows you to define detailed settings for the design:
Calculation According to Vogel/Heil
You can apply this method to determine the
- required shear panel stiffness Sreq
- critical lateral buckling force Ncr
- critical bending moment Mcr.
This plastic-plastic method of calculation is only applicable for pinned supports with uniaxial bending together with a load introduction on the upper flange. If the requirements are not fulfilled, for example in case of biaxial bending, RF-LTB displays an error message. Furthermore, it is possible to set the reduction factor kM for the bending moments My to 1.0 by conservative assumption if a rotational restraint is available.
Non-Designable Internal Forces
It is possible to neglect non-designable internal forces to exclude them from the analysis if the quotient of design force and plastic capacity falls below a certain value. In this way, you can ignore for example a low moment about the minor axis to avoid applying the method for biaxial bending.
Application Rule According to DIN 18800 Part 2, Element (320) and Element (323)
Automatic Determination of z
If you want to determine the factor used for the determination of the ideal elastic critical moment Mcr automatically, you can select one of the following options:
- Numerical solution of elastic potential
- Comparison of moment distribution diagrams
- Australian code AS 4100-1990
- U.S. standard AISC LRFD
When comparing the moment distribution diagrams, you can take advantage of the library with more than 600 diagrams listed in tables.