What kind of wind blows the roofs off the houses. Why did the hurricane blow away the roofs and stops so easily
In essence, the same thing happens when we bring a sheet of paper lying in our palm closer to our lips. If we blow on it, we will see it rise.
This is related to the so-called Bernoulli principle, named after the Swiss physicist Daniela Burnull and who first discovered it in 1738. When a liquid or liquid or gas moves at high speed, the pressure drops.
Airplane wings, for example, are designed so that the airflow from above them moves faster than from below. This causes a pressure drop which results in an effect called lift force.
Something similar happens in the case of the roof: when at high speed the air moves from above the roof, the pressure from 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. If air enters the house through the holes, 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 for the last 30 years hurricanes have become almost an ordinary phenomenon. You involuntarily ask yourself: is Moscow really going to have to be rebuilt after every storm? As far as the capital passed the test of strength, correspondents of "MK" found out.
Roofs. Wind in the city destroyed the roofs of 243 residential buildings. In some videos on the Web, you can see how the storm ruffles the iron roof of the house, like a thin sheet of paper. Even part of the roof of the Senate Palace in the Kremlin was demolished.
Roofs are covered according to building codes and regulations, but without taking into account the aging of its elements, - told MK Chief Engineer one of the major construction firms in Moscow. - The sheet iron of the roof is fastened with nails to the wooden crate. Over time, under the influence of snow load, the sun, the wooden crate dries out, the nails are no longer tightly held in the structure. And if you do not make repairs in due time, then the roof is blown away like this by gusts of wind. The second reason is the unscrupulous work of contractors.
As the expert assured, a competently assembled roof will not be blown away by gusts of at least 22, at least 30 m / s.
Everything is purely individual, - Alexander, an employee of one of the metropolitan firms for installing fences, explained to MK. - The fact is that the installation of fences in Moscow is due to many difficulties. This applies to the ground in which communications can be hidden. Therefore, it is impossible to dig deep, it is impossible to strengthen the pillar properly. Sometimes concreting is contraindicated. However, you need to understand that if this is an iron sheet, it means that 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 as a result of the elements. It is impossible to foresee.
Stops. One of the most terrible tragedies of the Moscow hurricane was the death of a man under a bus stop on Kirovogradskaya Street. In Mosgortrans, MK was told 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 had not been strengthened in any way and violated all conceivable methods of installation.
The 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 stand of the pavilion, 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, poured with concrete and covered with earth so that the racks are at asphalt level. A pavilion is put up, and already at the places where the plates are fastened, they are welded to the base by welding, decoratively poured with asphalt from above. But this pavilion was simply drowned in asphalt - there was no trace of a rigid attachment to the ground.
The expert explained that a well-installed pavilion, which is held in the ground by a kind of concrete anchor, will only carry away a tornado. It is very difficult to calculate what gust of wind a hastily dug-in stop will withstand. It can only be known practically.
You can’t attach anything to asphalt at all - it really doesn’t hold anything. But many companies simply save on installation. It's easier to just dig it into the asphalt, rather than dig a hole, boil, concrete... Normal installation will cost about 10-30 thousand, depending on the pavilion.
However, according to Mosgortrans, they have about 9,000 stops in Moscow on their balance sheet. And each, according to them, undergoes regular sanitary maintenance.
Compensation. The hurricane, which lifted rather heavy structures into the air, also damaged the facades of residential buildings. Some were left without windows. Will people be able to get compensation for damaged property?
The Department of Housing and Public Utilities told us that the payment of compensation is outside their area of responsibility, and recommended that we contact the mayor's office or the prefecture.
The prefecture of the Central Administrative District replied that there was no special order from the mayor's office on the issue of compensation, however, if it arrives, the authorities will certainly organize the issuance of money.
Andrey VAGANOV, General Director of the Happy People advisory centers, told MK that in this case it is necessary to understand what exactly was affected - personal or collective property. If, for example, your ceiling is leaking because the roof of the house has been torn off, then management companies should deal with this. If the glass in the apartment is broken, then this is already personal property. If the apartment is bought, then everything that happens within its perimeter is your property, and you are responsible for it. That is, it 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 of a natural disaster, write a statement and be sure to get a certificate from the relevant authorities that it was a hurricane. Such certificates are usually issued either by the Ministry of Emergency Situations or the Meteorological Service.
The main volume of appeals to insurance companies is associated with the risk of damage to property. This was announced by the President of the All-Russian Union of Insurers (VSS) Igor Yurgens. In most insurance programs - both property (casco, house or apartment insurance) and personal (life, health, accident) - the risk of damage from a hurricane is included in the standard coverage. In Moscow, the penetration rate of home insurance is the highest in Russia - it is about 50%. “Citizens who have insured their homes under this insurance program are eligible for payments in case of damage to their homes as a result of a hurricane. Such damage can be, for example, broken glass in the windows or flooding of the apartment as a result of damage to the roof,” the President of the ARIA explained.
Digit of the day
1 million rubles will be given to the families of those killed by the hurricane on May 29. The order on material assistance was 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 500,000 rubles each. And those who received medical care on an outpatient basis - 100 thousand rubles. In addition, children living in Moscow who have lost one of their parents as a result of the hurricane will receive monthly additional compensation payments of 13,000 rubles a month. Expenses for the burial of the dead within the city or for their identification and transportation for burial outside the capital will also be paid from the city budget.
Living on the coast is a dream for many people. However, in such regions, as in mountainous areas, near a lake or river, strong winds. And this factor cannot be ignored when building a house roof.
Aerodynamic parameters
The angle of inclination of the slope is the most important value in calculating the loads on the roof. Lateral wind pressure on steep slopes can cause tipping.
The wind exerts less pressure on flatter structures with a slight slope. This roof shape is suitable for areas with strong winds.
But the air flow tends to lift and tear off a too sloping roof.
When the flow collides with an obstacle - and the structure crowning the building - a swirl 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 sloping roof can be partially protected from exposure - for example, with the help of a laid out parapet.
A competent project should be drawn up taking into account the geographical location of the building, the climate and the terrain. Wind resistance is also affected by windage. roofing material and the quality of fixing the elements of the truss system and the crate.
When erecting 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. It is achieved thanks to such elements as braces, braces, diagonal ties - depending on the type of construction in rafter system some or all of them may be used.
There are certain parameters for fastening a beam laid along the perimeter of the building. It is fixed to the wall different ways, and, moreover, at a certain distance from the edge. All fastenings - both 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 bearing walls building with metal pins will increase the resistance to wind load.
All should be additionally securely screwed 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 stiffness must withstand this pressure.
Also, the wind is engaged in the distribution of snow on the roof - and it distributes it unevenly, due to which more is swept into one area, and the snow pressure increases. Therefore, there should be no weak points in the entire roof structure.
One more important point: not only connections should be strong - it is necessary that the rafter legs are made of high-quality wood.
hipped roof
This view is best suited for a square at the base of the house.
but future owner housing should remember that in this case it will not be possible to equip the attic.
Two trapezoidal slopes and two triangular ones - this is how it usually crowns a rectangular house and has great wind resistance.
This option involves the use of diagonal supports - rafters, heading from the two ends of the ridge to the four corners of the house. Such a supporting frame is practically not subject to deformation.
The absence of gables significantly reduces the resistance to wind, which "slides" almost unhindered on the surface.
Dutch half hip type
It is characterized by trapezoidal pediments and slopes-hips cut from below.
It does not have such a sharp protrusion as the upper structure of the building: truncated end slopes increase the ability of the half-hip to withstand loads.
For the arrangement of such a roof, a lot of materials will not be required, and its installation will also be simple.
If you place the slope in the direction of the prevailing winds, it will be reliable: that is, on the leeward side should be the part that is lower. The same rule applies here: the greater the slope, the greater the wind load.
Roofing against hurricane winds
Sheet materials have many advantages, but at the same time - a large windage.
Soft bituminous tile
This coating is optimally suited for the upper structure of the building with the most complex configuration.
IN model range there are specially designed types that have a special shape - with enhanced resistance to wind loads. The shingles are not only glued, but also nailed with special nails - such an attachment to the base is as reliable as possible, and even withstands hurricane wind– up to 220 km/h.
The optimal value of the roof slope when using natural tiles is 30-60 degrees.
The main arguments in favor of or are its weight and small size. It is difficult for the wind to cope with the weight of the natural covering, but if the tiles are nevertheless 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 lower and upper rows, but also the tile tiles completely on the entire slope - with the help of brackets.