Technical Guidance Note (Level 1, No. 22): Biaxial bending in columns

The subject of this guide is the design of non-composite steel beams to BS EN 1993-1-1 – Eurocode 3: Design of Steel Structures – Part 1-1: General Rules for Buildings. It covers both restrained and unrestrained rolled steel ‘I’ and ‘H’ beam sections. This is the first in the series of Level 2 guides and as such,the reader is assumed to be familiar with the concepts explained in relevant Level 1 Technical Guidance Notes. (This article was updated in October 2016 to reflect errata issued since its original publication.)

Elements within a steel frame structure are at risk of buckling under load. If measures are not taken when designing steel elements that recognise this risk, then the likelihood of its failure is significantly increased. This Technical Guidance Note explains how steel elements are restrained against buckling and what the structural engineer should consider when analysing steel structures with respect to buckling resistance.

While the advancement of computer based analysis continues to grow exponentially within the field of structural engineering, the tools that are used to analyse structures by hand are no less relevant. Many would argue that such tools are even more vital today than they have ever been if we are to fully understand the output of analysis applications. With this in mind, this Technical Guidance Note describes one of the most powerful analysis tools available: moment distribution. Moment distribution is a method by which statically indeterminate structures are analysed elastically. It’s based on the relative stiffness of elements that make up a structure and shifts bending moments from one section of the structure to another until they become balanced. Once this balance has been achieved, the forces and bending moments within the structure are modelled. (This article was updated in October 2016 to reflect errata issued since its original publication.)