Technical Guidance Note (Level 1, No. 6): Notional loading (Equivalent Horizontal Forces)

This Technical Guidance Note concerns the derivation of snow load onto structures. It is based on Eurocode 1: Actions on Structures Part 1-3; General Actions – Snow Loads. With this Eurocode being focused on an action that is sensitive to environmental effects, the UK annex to it plays a significant role, as it makes reference to projected snow falls that are unique to the British Isles. There are a large number of variations and conditions the designer must be aware of when determining snow loads onto structures. As such, the reader is referred to the code text more frequently than in other Technical Guidance Notes. (This article was updated in October 2016 to reflect errata issued since its original publication.)

The twisting of elements within structures due to eccentric loading is something that is best avoided as far as is possible. Such actions develop torsion forces in elements against which they were not designed to withstand. This Technical Guidance Note concerns this buildability and detailing issue that structural engineers must become familiar with in order to avoid otherwise unforeseen problems that can lead to significant remedial works on site and in some cases failures.

This Technical Guidance Note acts as an introduction to the core design concepts that are found within the current codes of practice used within the UK. It also explains the relationship between each of the other guidance notes and how the reader is to navigate and use them. All of the subsequent notes make reference, be they direct or implied to this core guide; it is therefore imperative that anyone seeking to use these guides must be fully conversant with what is contained within this note.