1               Introduction

This software has been developed by SCI for the BCSA and Steel for Life. The software deals with the lateral-torsional buckling of beams subjected to in-plane transverse and axial loads. The software calculates the elastic critical moment (Mcr) and the elastic critical load (Ncr) which are important parameters when designing steel members.

The behaviour of the beam is modelled using the Finite Element method which divides the beam into a finite number of elements along its axis. The discretisation process generates nodes along the beam with the following buckling degrees of freedom at each node:

1.  Lateral displacement

2.  Torsional rotation

3.  Lateral flexural rotation

4.  Warping deformation

The calculation of the buckling load factor (mcr), by which the initial set of loads must be multiplied to obtain the buckling load set, is achieved by solving the linear eigenvalue problem derived from the potential energy equation expressed at the state of equilibrium (before buckling).

Software key features:

·    Cross sections can be mono-symmetric I-sections.

·    Cross section height can vary linearly along the beam.

·    Support conditions in the bending plane can be specified at any location along the beam.

·    Restraints can be specified at any location along the beam and at a distance from the shear centre.

·    Point, moment and trapezoidal distributed loads can be specified at any location along the beam.


It is important to note that although the software uses the term “Beam” on the interface to refer to the design member, the application of the software is not limited to beams, and it can be used to analyse steel members subjected to bending and axial loading.



Although care has been taken to ensure that the calculated values are correct, users should verify the output. The Steel Construction Institute and other parties associated with this software and website assume no responsibilities for errors or misuse of this software, or damage arising from use of this software.