ISO 4355 pdf download Bases for design of structures — Determination of snow loads on roofs
This International Standard specifies methods for the determination of snow load on roofs
It can serve as a basis for the development of national codes for the determination of snow load on roofs.
National codes should supply statistical data of the snow load on ground in the form of zone mapstables, or formulae.
The shape coefficients presented in this International Standard are prepared for design application, andcan thus be directly adopted for use in national codes, unless justification for other values is available.
For determining the snow loads on roofs of unusual shapes or shapes not covered by this InternationaStandard or in national standards, it is advised that special studies be undertaken. These can includetesting ofscale models in a wind tunnel or waterflume,especially equipped forreproducing accumulationphenomena, and should include methods of accounting for the local meteorological statistics. Examplesofnumerical methods, scale model studies,and accompanying statistical analysis methods are describedin Annex G.
The annexes describing methods for determining the characteristic snow load on the ground, exposurecoeficient, thermal coefficient, and loads on snow fences are for information only as a consequence otthe limited amount of documentation and available scientific results.
In some regions, single winters with unusual weather conditions can cause severe load conditions nottaken into account by this International Standard.
Specification of standard procedures and instrumentation for measurements is not dealt with in thisInternational Standard.
2 Normative references
The following documents, in whole or in part,are normatively referenced in this document and areindispensable for its application. For dated references, only the edition cited applies. For undatedreferences, the latest edition of the referenced document (including any amendments) applies.ISO 23941), General principles on reliability for structures
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.3.1characteristic value of snow load on the groundSoload with a specified annual exceedance probability
Note 1 to entry: It is expressed in kilonewton per square metre (kN/m2).
Note 2 to entry: ln meteorology the term “weight of the ground snow cover” is also used
coefficient which defines the amount and distribution of the snow load on the roof over a cross section of the building complex and primarily depends on the geometrical properties of the roof
value of snow load on roofs
function of the characteristic snow load on the ground, s 0 , and appropriate shape coefficients
Note 1 to entry: The value of s is also dependent on the exposure of the roof and the thermal conditions of the building.
Note 2 to entry: It refers to a horizontal projection of the area of the roof.
Note 3 to entry: It is expressed in kilonewton per square metre (kN/m 2 ).
basic? load? coefficient
coefficient defining the reduction of the snow load on the roof due to a slope of the roof, β, and the surface material coefficient, C m