Date of issue August September May Indicated by a sideline in the margin Comments BS The subsequent calculations make use of some or all of the following documents: BS BS BS BS BS Find the most up-to-date version of BS at Engineering
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As the basic on the ground at the site location and altitude the snow load on the ground is given for an assumed site snow load by a factor known as the snow load ground level altitude of m, it is necessary to shape coefficient in accordance with the following adjust the value for locations where the ground level equation: General 1 Scope This Part of BS gives minimum imposed roof loads for use in designing buildings and building components which are to be constructed and used in the UK and the Channel Islands.
This can be caused by following symbols apply.
Appendix B explains the the simultaneous drifts should not exceed the logical process behind the calculations. This new Part of BS now gives more information on imposed roof loads and in particular gives snow loading data separately, allowing account to be taken of the variation of snow in the United Kingdom 6399- the effect of redistribution of snow on roofs due to wind.
It should be the most onerous value arising than 2 m wide, may also be considered as a local from uniformly distributed snow on the roof slope projection. Local drifting against parapets should be determined 63399-3 accordance with Figure 6 or from the following in which all parameters are as defined in Figure 6.
BS _Loading for building-Part3 Imposed roof loads_图文_百度文库
ISOBases for design of structures — Determination of snow loads on roofs1. Code of practice for imposed roof loads ICS Code of practice for imposed roof loads Executive summary Code of practice for minimum imposed roof loads for use in designing buildings and building components. This Code models the actual drift shapes and load intensities by simplified linear distributions, based on assumptions on the amount of snow available to drift and limitations on the drift height.
The total snow load per metre width in all the simultaneous drifts should not exceed the product of the site snow load and the length of the building perpendicular to the valley ridges. The correction is based on Snow is naturally deposited in many different limited information which shows that the snow density is patterns on a roof depending upon the wind speed, increased when the snow forms in drifts. The snow load shape coefficients do not include any allowances for drifting at parapets or other obstructions as these should be treated independently see 7.
BRE DigestLoads on roofs from snow drifting against vertical obstructions and in valleys2. The effects of deflection under concentrated loads a a roof area no larger than m2 in plan; or need only be considered when such deflection would b a width no greater than 10 m and a pitched roof adversely affect the finishes.
Where the roof is to have access for specific usages the imposed loads for c and d above should be replaced by the appropriate imposed floor load as recommended in 5.
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The equations given in Figure 2 to Figure 9 for determining the snow load shape coefficients are empirical; where they are associated with local drifting of snow they include a correction to allow for an increased weight density in the drift.
This can result in more severe load imbalances occurring than those resulting from clause 5 which have been derived for natural deposition patterns. Users of British Standards should make sure that they possess the latest amendments or editions. This value is assumed to be conditions. NOTE If the structure is susceptible to asymmetric loading, the designer should also consider the possibility of drifts of differing severity in the valleys.
The factor is usually 5 or 8 depending upon the severity of drifting likely to occur for the design configuration being considered.
The snow load shape often necessary to consider several loading coefficients do not include any allowances for situations to ensure that all the critical load effects drifting at parapets or other obstructions as these are determined.
The designer should be aware that the deposition and redistribution of snow on roofs are very complex phenomena. For this case, the local drift every valley, although not necessarily from 7. NOTE However, where, for example, on a lower roof area sheltered from all wind directions, there is the possibility of redistribution of snow from a higher roof to form a local drift on top of a uniform snow load distribution on this lower roof, it would be appropriate to consider the local drift load acting in combination with the uniform snow load on the lower roof.
The appropriate Snow load shape coefficient m1 is the lesser of: CP 3, Code of basic data for the design of buildings1. In response to orders for international standards, it is BSI policy to supply the BSI implementation of those that have been published as British Standards, unless otherwise requested.
This subclause is an optional alternative to 4. This force should be taken into account in the design of snowguards or b if snow is likely to slide off the roof endangering people or property below.
For parapets, see 7. In some circumstances more than one bbs drift load case may be applicable for the same location on a roof in which case they should be treated as alternatives. Condition b can be caused by a redistribution of snow which affects the load distribution on the complete roof, e. Contact the Information Centre.
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It may result from either the uniform load case or the asymmetric load case. For above m specialist advice should be sought the redistributed snow load cases the distribution of see clause 1 and appendix C.
Meteorological Office are as follows. Summary of pages This document comprises a front cover, an inside front cover, pages i to iv, pages 1 to 22, an inside back cover and a back cover.