Why does the wind blow roofs off? Rafters and roofing that can withstand strong winds. Soft bitumen shingles
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In essence, the same thing happens when we bring a piece of paper lying on our palm closer to our lips. If we blow over it, we will see it rising.
This is due to the so-called Bernoulli's principle, named after the Swiss physicist Daniel Bernoull and, who first discovered it in 1738. When a liquid or liquid or gas moves on high speed, the pressure drops.
Airplane wings, for example, are designed so that the air flowing over them from above moves faster than from below. This causes a pressure difference, which leads to an effect called lifting force.
Something similar happens in the case of a roof: when air moves at high speed from above the roof, the pressure above becomes less than inside the house. This is a simple effect where a force causes a structure to move upward.
But it may happen that the pressure difference is not enough for the roof to rise up. If air enters the house through openings, the pressure equalizes and consequently the roof of the house collapses or falls down.
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It has become a very windy city. In the middle of the 20th century, storms, squalls and tornadoes were unheard of, but over the last 30 years, hurricanes have become almost an ordinary occurrence. You can’t help but wonder: will Moscow really have to be rebuilt after every storm? MK correspondents found out how well the capital passed the test of strength.
Roofs. The wind destroyed the roofs of 243 residential buildings in the city. Some videos on the Internet show how a storm shakes the iron roof of a house, as if thin sheet paper. Even part of the roof of the Senate Palace in the Kremlin was demolished.
Roofs are covered according to building regulations and rules, but without taking into account the aging of its elements, - said MK Chief Engineer one of the major construction companies Moscow. - Sheet iron The roof is fastened with nails to the wooden sheathing. Over time, under the influence snow load, sun wooden sheathing It dries out and the nails no longer hold tightly enough to the structure. And if repairs are not carried out in due time, then the roof is blown away by gusts of wind. The second reason is the unscrupulous work of contractors.
As the expert assured, a properly assembled roof will not be blown away by gusts of at least 22 or 30 m/s.
“Everything is purely individual,” explained Alexander, an employee of one of the capital’s fence installation companies, to MK. - The fact is that installing fences in Moscow is caused by many difficulties. This applies to the ground in which communications may be hidden. Therefore, you cannot dig deep; you cannot strengthen the pillar properly. Sometimes concreting is contraindicated. However, you need to understand that if it is an iron sheet, it means there will be a load in the form of a “sail” from the wind, the risk is high. When installing fences, our warranty states that we are not responsible for damage resulting from the elements. This cannot be foreseen.
Stops. One of the most terrible tragedies of the Moscow hurricane was the death of a man under a bus stop on Kirovogradskaya Street. Mosgortrans told MK that the stop was installed “in strict accordance with existing standards for the placement of such structures.” However, the company that produces bus pavilions explained that the stop on Kirovogradskaya was not strengthened in any way and violated all conceivable installation methods.
The bus stop pavilion has two mounting options, the expert told MK. - If the base is reinforced concrete (which was not there, judging by the photographs), then a 3-5 mm metal plate is made under each pavilion stand, there are 4 holes in the corners, and each stand is attached to the slab. If there is no such foundation (judging by the photo, this is exactly the situation), then a hole of 50–60 cm is dug, reinforcement is installed, a plate is welded on top of it, filled with concrete and covered with earth so that the posts are at the level of the asphalt. The pavilion is erected, and at the mounting points the plates are welded to the base, and the top is decoratively filled with asphalt. But this pavilion was simply buried in the asphalt - there was no sign of a rigid connection to the ground.
The expert explained that a properly installed pavilion, which is held in the ground by a kind of concrete anchor, will only be carried away by a tornado. It is very difficult to calculate how much gust of wind a hastily dug stop will withstand. The only way to find out is practically.
You can’t attach anything to the asphalt at all - it doesn’t really hold anything. But many companies simply save on installation. It’s easier to just dig it into the asphalt, rather than dig a hole, weld it, concrete it... Normal installation will cost about 10-30 thousand, depending on the pavilion.
However, as Mosgortrans said, they have about 9 thousand stops in Moscow on their balance sheet. And each, they say, undergoes regular sanitary maintenance.
Compensation. The hurricane, which lifted quite heavy structures into the air, also damaged the facades residential buildings. Some were left without windows. Will people be able to receive compensation for damaged properties?
The Housing and Communal Services Department told us that payment of compensation was outside their area of responsibility and recommended that we contact the mayor’s office or the prefecture.
The prefecture of the Central Administrative District responded that there is no special order from the mayor’s office on the issue of payment of compensation, however, if it is received, the authorities will certainly organize the issuance of money.
General Director of Advisory Centers " Happy people"Andrei VAGANOV told MK that in in this case you need to understand what exactly was damaged - personal property or collective property. If, for example, your ceiling is leaking because the roof of the house was torn off, then management companies should take care of this. If a glass in an apartment is broken, then this is personal property. If an apartment is purchased, then everything that happens within its perimeter is your property, and you are responsible for it. That is, this is a question of apartment insurance. If the apartment is insured and a hurricane is an insured event, then you need to film all the consequences natural disaster, write a statement and be sure to get a certificate from the relevant authorities stating that it was a hurricane. Such certificates are usually issued by either the Ministry of Emergency Situations or the Meteorological Service.
The bulk of requests to Insurance companies associated with the risk of damage to property. This was announced by the President of the All-Russian Union of Insurers (VSU) Igor Yurgens. In most insurance programs - both property (hull insurance, home or apartment insurance) and personal (life, health, accident) - the risk of damage from a hurricane is included in standard coverage. In Moscow, the penetration level of home insurance is the highest in Russia - it is approximately 50%. “Citizens who have insured their homes under this insurance program are entitled to payments in the event of damage to their homes as a result of a hurricane. Such damage could be, for example, broken glass in the windows or flooding of the apartment as a result of damage to the roof,” explained the president of the VSS.
Digit of the day
1 million rub. will be received by the families of those killed due to the hurricane on May 29. Order on financial assistance signed by Moscow Mayor Sergei Sobyanin. In accordance with the document, compensation will also be paid to victims hospitalized in city hospitals: they are entitled to 500 thousand rubles. And to those who were given health care on an outpatient basis - 100 thousand rubles. In addition, children living in Moscow who lost one of their parents as a result of the hurricane will receive additional monthly compensation payments of 13 thousand rubles per month. The costs of burying the dead within the city or identifying and transporting them for burial outside the capital will also be paid from the city budget.
Living on the seaside is a dream for many people. However, in such regions, as well as in mountainous areas, strong winds often blow near a lake or river. And this factor cannot be ignored when building the roof of a house.
Aerodynamic parameters
The slope angle is the most important value when calculating roof loads. Lateral wind pressure on steep slopes may cause it to tip over.
The wind puts less pressure on flatter structures with a slight slope. This roof shape is suitable for areas with strong winds.
But the roof is too shallow air flow tends to lift, tear down.
When the flow collides with an obstacle - and the structure crowning the building - a vortex occurs: without going into details, we can say that two tangential forces and one lifting force act on the roof. The value of each of these forces depends on the angle of inclination of the slope. A flat roof can be partially protected from exposure - for example, using a laid parapet.
A competent project must be drawn up taking into account geographical location buildings, climate and terrain. Wind resistance is also affected by windage roofing material and the quality of fastening the elements of the rafter system and sheathing.
When constructing the frame, it is not allowed to use any substrates or other parts that can deform over time.
To prevent the roof from being torn off or overturned by a gust of hurricane wind, it must have maximum stability. This is achieved thanks to elements such as braces, struts, diagonal braces - depending on the type of structure in rafter system some or all of them may be used.
Exist certain parameters fastening timber laid around the perimeter of the building. It is fixed to the wall different ways, and at a certain distance from the edge. All fastenings - both the rafters to the Mauerlat and the Mauerlat itself to the wall - must be done carefully.
Additional fastening of the lower ends of the rafter legs to load-bearing walls buildings using metal pins will increase resistance to wind loads.
Everything must be additionally securely fastened with wire twists - if strong winds prevail in the area, and after one - if moderate wind pressure is expected.
Different sections of the roof experience different wind loads– the rigidity must resist this pressure.
The wind also distributes snow on the roof - and it distributes it unevenly, due to which more snow is blown onto some areas, and the snow pressure increases. Therefore, throughout roofing structure there should be no weak points.
Another important point: not only connections must be strong - it is necessary that rafter legs were made of high quality wood.
Hip roof
This type is optimal for a house with a square base.
However, the future homeowner must remember that in this case it will not be possible to equip the attic.
Two trapezoidal slopes and two triangular ones - this is what the crown usually looks like rectangular house and has great wind resistance.
This option involves the use of diagonal supports - slanted rafters, running from the two ends of the ridge to the four corners of the house. Such load-bearing frame practically not subject to deformation.
The absence of gables significantly reduces resistance to the wind, which “slides” almost unhindered over the surface.
Dutch half hip type
They are characterized by trapezoidal pediments and hip slopes cut off from the bottom.
It does not have such a sharp protrusion as top structure buildings: truncated end slopes increase the ability of the half-hip to withstand loads.
To arrange such a roof you will not need a lot of materials, and its installation will also be simple.
If you position the slope in the direction of the prevailing winds, it will be reliable: that is, on the leeward side there should be the part that is lower. The same rule applies here: the greater the slope, the greater the wind load.
Roof covering against hurricane winds
Sheet materials have many advantages, but at the same time they have a high windage capacity.
Soft bitumen shingles
This coating is optimal for the upper structure of a building with the most complex configuration.
IN model range There are specially designed types that have a special shape - with increased resistance to wind loads. The shingles are not only glued, but also nailed with special nails - such fastening to the base is as reliable as possible and can withstand even hurricane wind– up to 220 km/h.
The optimal value of the roof slope when using natural tiles considered 30-60 degrees.
The main arguments in favor of or are its weight and small sizes. The wind finds it difficult to cope with the weight natural coating, however, if the tiles are torn off, in the event of a fall, this very weight will become a serious threat.
You can increase reliability by securing not only the bottom and top rows, but also the tiles completely along the entire slope - using staples.