FAQ 000088 EN

Calculation RF-FE-LTB FE-LTB

When I tried to pick the imperfections in FE-LTB, the message "Diagonal coefficient of matrix < 0"="" was=""> What have I done wrong?

Answer

This message shown in FE-LTB means that your system is numerically unstable.

Often, such an instability in FE-LTB can be explained by inaccurate support conditions or release definitions.

The determination of the critical load factor provides the stability load of the analyzed structural system.

In the numerical calculation, this stability load is characterized by the fact that either the determinant of the stiffness matrix becomes zero, or that very high deformations occur for very small load increases in the calculation.
RFEM Steel and Aluminium Structures
RF-FE-LTB 5.xx

Add-on Module

Lateral-torsional buckling analysis of members according to the second-order analysis (FEM)

RSTAB Steel and Aluminium Structures
FE-LTB 8.xx

Add-on Module

Lateral-torsional buckling analysis of members according to the second-order analysis (FEM)