I have a choice of Standards to use for my wind loading, which is most suitable?
There are three ways in total provided for you to define a wind load in KeyPOST. The first, a fixed wind load, is likely to be used if you have been given this by a colleague with structural design expertise, or if you are working for a client who requires you to use a specific value.
That apart, there are two Standards that apply, and provide guidance on how to arrive at a wind load. These are BS EN 12899-1:2007, which applies very specifically to fixed, vertical traffic signs, and BS EN 1991-1-4:2005 (also known as Eurocode 1) which applies to any structure up to 200m in height, e.g. bridges, buildings and, of course, traffic signs!
12899 vs. 1991
In order to simplify things for specifiers of traffic signs 12899 includes advice when used in the UK about wind loads that are applicable in England, Wales, Scotland etc.. At that level, the advice has to take account of a wide variety of terrain, altitude and orography (hills, escarpments and ridges). This conservative approach may be all that is available where detailed information about the site proposed for a sign structure.
If detailed information is available then a more refined, and often significantly lower wind load can be used, with confidence, by employing 1991 (Eurocode 1). Whilst this Standard can be quite onerous to implement, software is readily available to simplify the process and to provide the necessary wind speed data, and KeyPOST also provides for this. As such, it is very unlikely that you will not see a significant cost benefit by using Eurocode 1.
Note - To use Eurocode 1, it is necessary to create an ‘environs’ that includes the relevant information to enable it. See a separate knowledge base article covering this process, as well as the on-line help manual.