Lateral-torsional buckling settings

LTB restraints are supports against lateral-torsional buckling (LTB) at the top or bottom flange of the beam. The topside is defined by the positive local z- axis of the section. It means that for a positive My (which causes compression at the topside) the LTB length (and the related moment) is calculated by the position of the stiffeners at the topside. The bottom side is defined by the negative local z-axis of the section. It means that for a negative moment My (which causes compression at the bottom side) the LTB length (and the related moment factors) is calculated by the position of the stiffeners at the bottom side. When no LTB stiffeners are defined, the values, introduced in the Buckling data dialog are used.

Name

Defines the name of restraint.

Position z

Specifies the position in Z direction, i.e. either the topside or the bottom side.

Geometry

Position x

Defines the position of the restraint.

If more than one restraint is being used, this value specifies the position of the first restraint.

Coord. definition

The position can be input in absolute or relative coordinates.

Repeat

Defines the number of restraint.

This number includes the restraint at the beginning and at the end of the defined interval. If the "on begin" restraint or the "on end" restraint is not included, the actual number of defined restraint is lower (by one or two) than the value defined here.

Regularly

If ON, the restraints are distributed regularly over the length of the beam.

If NOT, the following parameter (Delta x) specifies the distance between the adjacent restraints.

Delta x

This value specifies the distance between the adjacent restraints.

On begin

If ON, the first restraint is defined.

If OFF, the first restraint is not included.

On end

If ON, the last restraint is defined.

If OFF, the last restraint is not included.
The procedure to adjust the LTB data

  1. Open service Aluminium:

  1. either using tree menu function Aluminium,

  2. or using menu function Tree > Aluminium.

  1. Select function Beams >Stability Check Data > LTB restraints and open it.

  2. Type required values and select appropriate options.

  3. Confirm with [OK].

  4. Select the member where the data are to be defined.

  5. End the function.