Why the hurricane blew off roofs and stops so easily & nbsp. Rafters and roofs that can withstand strong winds Why hurricane tears off roofs
Living on the seaside is a dream for many people. However, in regions such as in mountainous areas, strong winds often blow near a lake or river. And this factor cannot be ignored when building a house roof.
Aerodynamic parameters
The slope of the slope is the most important value when calculating roof loads. Lateral wind pressure on steep slopes may cause rollover.
The wind puts less pressure on flatter structures with a slight incline. This roof shape is suitable for areas with strong winds.
But the air flow tends to lift, tear off too flat roof.
When the stream collides with an obstacle - and the structure crowning the building - a swirl occurs: without going into details, we can say that two shear 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 impact - for example, using a lined parapet.
A competent project should be drawn up taking into account the geographical location of the building, the characteristics of the climate and the terrain. Wind resistance is also affected by windage. roofing material and the quality of fastening the elements of the rafter system and the lathing.
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, struts, diagonal ties - depending on the type of construction in rafter system some or all of them can be used.
There are certain parameters for fastening the timber laid along the perimeter of the building. It is fixed to the wall in various ways, and, moreover, at a certain distance from the edge. All fastenings - both the rafters to the Mauerlat, and the Mauerlat itself to the wall - must be performed carefully.
Additional fastening of the lower ends of the rafter legs to load-bearing walls buildings with metal pins will increase the resistance to wind load.
All should be additionally securely fastened with wire strands - if strong winds prevail in the area, and one after another - if moderate wind pressure is expected.
Different sections of the roof experience different wind loads - the rigidity must withstand this pressure.
Also, the wind is involved in the distribution of snow on the roof - and it distributes it unevenly, due to which more is swept over some areas, and the snow pressure increases. Therefore, throughout roof 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 quality wood.
Hipped roof
This type is optimal for a house with a square base.
However, the future homeowner should remember that in this case it will not be possible to equip the attic.
Two trapezoidal slopes and two triangular - this is what it looks like, usually crowning a rectangular house and having great wind resistance.
This option involves the use of diagonal supports - slanting rafters going from 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 "glides" over the surface almost unhindered.
Dutch type of half hip
It is characterized by trapezoidal pediments and hips cut from the bottom.
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.
To equip such a roof, you do not need a lot of materials, and its installation will also be simple.
If the slope is placed in the direction of the prevailing winds, it will be reliable: that is, on the leeward side there should be the part that is below. The same rule applies here: the greater the slope, the greater the wind load.
Roof covering against hurricane wind
Sheet materials have many advantages, but at the same time they have great wind capacity.
Soft bituminous shingles
This coating is ideal for the top structure of a building with the most complex configuration.
The model range includes specially designed species with a special shape - with enhanced resistance to wind loads. 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 winds - up to 220 km / h.
The optimal value of the roof slope when using natural tiles is considered to be 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 torn off, in the event of a fall, this very weight will become a serious threat.
You can increase the reliability by fixing not only the lower and upper rows, but also the tile tiles completely on the entire slope - using brackets.
In essence, the same thing happens when we bring a piece of paper closer to our palm with our lips. If we blow over it, we will see it as it rises.
This is due to the so-called the Bernoulli principlenamed after a Swiss physicist Daniela Bernoulland 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 air flow from above moves faster than from below. This causes a pressure drop, which leads to an effect called lifting force.
Something similar happens in the case of the roof: when air moves at high speed from the top of the roof, the pressure from above becomes less than inside the house. This is a simple effect where force causes the structure to move upward.
But it may happen that the pressure difference is not enough for the roof to go up. If air enters the house through the vents, the pressure is equalized and therefore the roof of the house collapses or falls down.
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Has become a very windy city. In the middle of the 20th century, storms, squalls and tornadoes were never heard of, but for the last 30 years hurricanes have become almost an ordinary phenomenon. One involuntarily wonders: will Moscow have to be rebuilt after each storm? Correspondents of "MK" found out how the capital withstood the test of strength.
Roofs. The wind in the city destroyed the roofs of 243 residential buildings. Some videos on the web show 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 reckoning on the aging of its elements, - said "MK" chief engineer of one of the largest construction firms in Moscow. - The sheet metal of the roof is fastened with nails to the wooden battens. Over time, under the influence of snow load, sun wooden lathing it dries up, the nails are no longer tight enough in the structure. And if you do not make repairs in due time, then the roof is blown away like that by gusts of wind. The second reason is the unfair work of contractors.
As the expert assured, a competently assembled roof in gusts at least 22, even 30 m / s will not blow off.
Everything is purely individual, - explained to "MK" Alexander, an employee of one of the capital firms for the installation of fences. - 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 deeply, it is not possible to strengthen the pillar properly. Sometimes concreting is contraindicated. However, you need to understand that if it is an iron sheet, then 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 caused by the elements. It is impossible to foresee this.
Stops. One of the worst tragedies of the Moscow hurricane was the death of a man under a bus stop on Kirovogradskaya Street. In Mosgortrans "MK" said that the stop was installed "in strict accordance with the existing norms for the placement of such structures." However, the company that manufactures bus pavilions explained that the stop on Kirovogradskaya was not reinforced in any way and violated all conceivable installation methods.
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 plate of 3–5 mm metal is made for each pavilion stand, 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 posts are at the level of asphalt. A pavilion is erected, and already at the points of attachment, the plates are welded to the base by welding, from above it is decoratively filled with asphalt. But this pavilion was simply drowned in the asphalt - there was not even a trace of rigid attachment with 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 what gust of wind a hurried stop will withstand. You can only find out 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, and not dig a hole, cook, concrete ... Normal installation will cost about 10-30 thousand, depending on the pavilion.
However, as they said in Mosgortrans, they have about 9 thousand 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. Someone was left without windows. Will people be able to get compensation for damaged property?
In the Department of Housing and Utilities, we were told that compensation payments are outside their area of \u200b\u200bresponsibility, and they advised us to contact the mayor's office or the prefecture.
The prefecture of the Central Administrative District replied that there is no special order from the mayor's office on the payment of compensation yet, however, if it is received, the authorities will certainly organize the issuance of money.
Andrey VAGANOV, General Director of the Happy People consultative centers, told MK that in this case it is necessary to understand what specifically suffered - personal property or collective property. If, for example, your ceiling is leaking because the roof of your house has been blown off, then management companies should do this. If the glass in the apartment is broken, then this is already 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, it is a question of apartment insurance. If the apartment is insured and a hurricane is an insured event, then you need to shoot all the consequences of a natural disaster, write a statement and be sure to take a certificate from the relevant authorities that it was a hurricane. Such certificates are usually issued or Ministry of Emergencies , or the Weather Service.
The main volume of applications to insurance companies is associated with the risk of causing damage to property. This was announced by the President of the All-Russian Union of Insurers (ARIA) Igor Yurgens. In most insurance programs - both property (comprehensive, home or apartment insurance) and personal (life, health, accident) - the risk of hurricane damage is included in the standard coverage. In Moscow, the penetration rate of home insurance is the highest in terms of Of Russia - it is about 50%. “Citizens who have insured their homes under this insurance program are entitled to benefits in the event of damage to their homes as a result of a hurricane. Such damage can be, for example, broken glass in the windows or the bay of an apartment as a result of damage to the roof, ”explained the President of the ARIA.
Digit of the day
1 million rubles will receive the families of those killed in the hurricane on May 29. The order on material assistance was signed by the mayor of Moscow 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 each. And those who received medical assistance 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 be assigned additional monthly compensation payments of 13 thousand rubles a month. The costs of burying the dead in the city or identifying and transporting them for burial outside the capital will also be covered by the city budget.
