Wind Loading – BS6399: Part 2: 1997 incorporating amendment No.1.
BS6399 replaced CP3: Chapter V: Part 2 (now withdrawn) with two alternative methods:
- A standard method, which uses a simplified procedure
- A directional method, from which the simplified method was derived.
On most insulated panel cladding projects the simplified method will be adequate, it allows the wind loads to be calculated for:
The structure as a whole
- Individual elements – roof and wall
- Individual cladding units
The basic wind speed Vb m/s is obtained from a chart of the UK expressed as an hourly mean value. Site altitude and topographic dimensions have to be taken into consideration in calculating the effective wind speed, this work will normally be completed by a qualified engineer familiar with the site and building design.
The effective wind speed calculated for the building design and location is converted into wind loads for roof and wall zones using a series of figures for typical building shapes. The range and detail of these building shapes has been enlarged from those available in CP3.
A typical duo-pitch roof will have up to ten different pressure zones, on very large roofs it may be possible to vary the purlin spacing to suit the design loads. The critical design value for insulated panels is usually the fastener attachment strength on roofs and corner zones of walls.
Example – Use of Calculated Design Loads
Consider the industrial unit which is to be built on the outskirts of Birmingham. It is to have a steel frame and will be clad with KS1000 RW roof and KS1000 MR wall panels.
Kingspan technical department will be able to calculate the design wind loads for the building when provided with the following information building location dimensions for plan and elevation details of local topography.
Based on the design wind speed map see page 120, Kingspan will calculate the design loadings for the relevant roof and wall zones e.g.
The typical design loads for the walls are:
- Pressure (general zones) = 0.72 kN/m²
- Suction (general zones) = 0.51 kN/m²
- Suction (corners) = 0.72 kN/m²
The typical design loads for the roof are:
- Dead load = 0.11 kN/m²
- Imposed (including snow) = 0.60 kN/m²
- Wind suction (general zones) = 1.00 kN/m²
- Wind suction (eaves & gable) = 1.20 kN/m²
The design values for each zone should then be checked against the permitted maximum loads based on Kingspan load span tables (see relevant roof or wall sections) and the fastener strengths.
Basic Wind Speed for UK & Ireland
Map of United Kingdom showing basic wind speed in m/s - maximum gust speed likely to be exceeded on the average only once in 50 years at 10m above the ground in open level country.
Map taken from BS6399: Part 2: 1997