The territory of Russia occupies a huge area. Depending on the intensity of wind and snow exposure, it is customary to distinguish between wind and snow regions of Russia, each of which, according to the results of comprehensive studies, is assigned a certain category.
Snow zones of Russia
The location of certain zones on the map of Russia, their geological and geographical features served as a starting point for zoning the entire territory of the country according to the degree of precipitation intensity. There are 8 snow zones. As the load on the territory increases, an index with a large digital value is assigned. The smallest amount of precipitation corresponds to the index "1". The density of snow cover in such areas is 70–80 kg / m 2 . The maximum level of snow load in the regions of Russia corresponds to the eighth category. In this case, the highest density of precipitation is observed, which can reach 550 kg / m 2 . A detailed classification of such areas is presented in the table of snow regions of Russia.
Russian wind zones
The movement of air masses over the territory of the Russian Federation is uneven. One of the key factors influencing the movement of air flows is the topography of the site. Geographic features of the area and a number of other features formed the basis for the classification of wind zones in Russia. The criterion for this distinction is the level of wind pressure. It is customary to distinguish 7 districts.
The minimum pressure is fixed in zones with an index "1". Its highest mark is observed in areas under the number "7".
Load concept
The ranking of Russian regions according to the degree of snow and wind intensity is of great importance in the design and construction of residential buildings, industrial facilities and other structures. The affiliation of a particular area to a particular zone is a determining factor in choosing the appropriate methods for erecting a foundation, supporting structures and roofing elements of a building.
1. Wind load
Under the wind load, first of all, we mean the total indicator of pressure exerted on the building elements. When calculating the average wind load, a number of key factors are taken into account. Among them:
- the speed of movement of air masses;
- design features;
- high-rise characteristics of the building.
The final value of the wind load, to one degree or another, consists of two main parameters: the average and ripple component. The first component is calculated from the standard value of wind pressure, depending on the height characteristics of the building. The second component is determined taking into account the configuration of the structure and dynamic pressure parameters.
It is also worth noting that the wind effect is also taken into account when operating various high-altitude types of equipment, for example, a crane. In this case, the maximum permissible limit values are taken as the operating parameters of the load on all its nodes and mechanisms.
2. Snow load
This type of natural impact plays a paramount role in the construction of roofing elements. The calculated data in this case consists of two quantities: the density of the snow cover and its pressure.
According to precipitation rates, it is customary to distinguish 5 snow regions of Russia. The regions characterized by high rainfall include the Murmansk region, the Kirov region, the Komi Republic, and Bashkortostan. The lowest intensity is traced in the Amur region, Buryatia and the Trans-Baikal Territory.
A significant impact on the level of snow load has a wind. In areas with a predominance of the latter, the load is noticeably reduced. This is due to the fact that the snow does not have time to accumulate on the roof of the building, but simply blown away by gusts of wind.
Wind and snow loads in the regions of Russia are graphically presented on the corresponding maps.
Snow load
When installing roofing elements of buildings, it is necessary to calculate this load. This approach will preserve the integrity of the load-bearing elements of the roof and save the owner from unjustified expenses.
For carrying out the settlement operations, a number of parameters will be required: the weight of the snow cover P per 1 m 2 , the degree of roof slope u.
The formula for calculating the total snow load is as follows:
S = P * u
Existing data in SNiP on snow load by regions of Russia can be used both by specialists and ordinary people. The value of u is variable. This coefficient is taken into account only for roofs with an inclination angle of not more than 60 0 .
Wind load
The presented parameter is necessary primarily in the design of roof systems of houses. In accordance with SNiP, the wind load is a combination of the following physical quantities:
- rated pressure affecting the inside of the building;
- friction forces acting tangentially to the surface of the building;
- pressure on the outside of the building.
To calculate the average value of the wind load, two quantities will be required: a coefficient indicating the degree of pressure exerted depending on a given height k, and the pressure P 0 established for a given area. The final formula is as follows:
P = P 0 * k
The value of P 0 is indicated in the table compiled for most regions of Russia.
Nevertheless, there are some areas of the country for which this parameter is not given in the table. We are talking about mountainous regions and territories that differ in harsh climatic conditions. The standard degree of wind load for such zones is derived by the formula:
P 0 = 0.61 V 2 ,
where V is an indicator of the speed of air masses at an altitude of 10 m, corresponding to an estimated time of 10 minutes.
Auxiliary methods of calculation
In addition to the presented methodology for calculating the average value of wind and snow load in a specific region of Russia, there are a number of techniques that allow us to calculate this parameter using other physical quantities.
The first method is applicable to determine the wind load. Initially, it is required to find the wind pressure according to the following formula:
Pr = 0.00256 * V 2 ,
where V is the wind speed.
The next step is to find the drag coefficient. Depending on the type of roof, its value may vary:
- for elongated vertical - 1.2;
- for shortened vertical - 0.8;
- for elongated horizontal - 2.0;
- for a shortened horizontal - 1.4.
The final stage of the calculations is the combination of the above values into a single formula:
P = A * Pr * C,
where A is the surface area exposed;
C - frontal resistance.
To obtain a more reliable result when calculating the snow load, the above formula can be supplemented with several auxiliary values:
S = P * u * s t * c e ,
where c t is the thermal coefficient;
c e - coefficient taking into account the error during snow drift under the influence of wind.
All the parameters presented are in the public domain in regulatory documents approved at the legislative level.
Snow and wind impact on roof structures
The high density of snow regions of Russia contributes to the development of more advanced types of roof structures and methods of their installation.
One of the key features of the roof in this case is a slope. Oddly enough it sounds, but much more snow can accumulate on an inclined surface than on a flat one. During a storm or a blizzard, snow masses under the influence of air currents, overcoming the ridge of the roof, lie on the leeward side. In this place of snow, as a rule, much more than on the opposite side.
It is worth mentioning about the so-called "snow bags". They occur at the intersection of roofs and at dormers. Rafter structures in such places need additional reinforcement. The lathing should be made in the form of a continuous flooring, and the rafters are reinforced with additional racks.
The degree of intensity of a snow and wind region of Russia is variable. The fact is that under the influence of certain external factors, the level and nature of precipitation in a particular territory can undergo serious changes. This circumstance must be taken into account by specialists. After careful research, the necessary regulatory changes are made.