Technical Guidance Note (Level 2, No. 21): Design and detailing of base plates to steel columns

This Technical Guidance Note addresses the design of timber elements that are unrestrained against lateral torsional buckling. It explains how such beams are analysed and designed. The impact of notching the supports of beams is also considered with respect to the shear capacity of the beam. For clarity and brevity, this note only covers solid and glued laminated (glulam) timber elements; compound and composite beams, such as flitch beams, are not considered. The connections within timber frame assemblies will be addressed in a future note. Readers should also be aware that this note forms part of a trio of Technical Guidance Notes leading to the design of bespoke timber trusses – assemblies made from unrestrained timber beams and posts. Notes on the design of timber posts and bespoke timber trusses will follow later in the series.

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.)

The design of timber posts follows the same principles as the design of vertical structural elements formed from other materials. Extreme fibre stresses or buckling due to applied axial forces are the key components affecting a post’s ability to perform. The major difference is the anisotropic nature of timber, which, for vertical elements, has a significant impact on the assessment of their performance as a structural member. The design of timber elements in the UK, according to current codes of practice, is based on limit state theory. This Technical Guidance Note adopts this approach to describe the design of timber posts. The note assumes that the reader is familiar with the use of coefficient factors prevalent within BS EN 1995-1-1 (Eurocode 5), as described in Technical Guidance Notes Level 1, No. 18 Design of timber floor joists and Level 2, No. 14 Design of unrestrained timber beams.