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10Рисунок 6 - Устройство железобетонной перемычки
Кирпичные здания являются наименее сейсмостойкими, и как правило подвергаются большей опасности повреждений при сейсмической активности. Именно поэтому к ним предъявляются дополнительные меры по понижению этажности и значительному усилению.
Заключение:
Проанализировав различные технологии возведения зданий и сооружений в Республике Хакасия можно сделать вывод, что благодаря применению дополнительных конструктивных решений и усилению уже построенных объектов недвижимости можно обеспечить безопасность и надежность застройки в существующих условиях сейсмической активности.
СПИСОК ЛИТЕРАТУРЫ:
1. СНиП 11-7-81*. Строительство в сейсмических районах. Госстрой России, М.: 2002.
2. Закон Республики Хакасия от 28 июня 2006 г. N 29-ЗРХ "Об утверждении республиканской целевой программы "Сейсмобезопасность территории Республики Хакасия" на 2006 - 2010 годы" (с изменениями от 25 декабря 2007 г.)
3. Оценка влияния грунтовых условий на сейсмическую опасность. Методическое руководство по сейсмическому микрорайонированию (под ред. О.В. Павлова). М.: Наука, 1988. 244 с.
4. Смирнов В.И., Доклад по четвертому вопросу повестки дня «Инновационные системы сей-смозащиты зданий и сооружений в Российской Федерации и за рубежом» 2009.
5. Строительство в сейсмических районах [электронный ресурс] -http ://rusbuildrealty.ru/books/arhitektura/124.html
6. Дятков С.В., Михеев А.П. Архитектура промышленных зданий. - 4-е изд., перераб. и доп. Учебник. - М.: Издательство Ассоциации строительных вузов, 2008. - 560с.
УДК 711:605.031.3
THE PROBLEMS OF AIRING CITIES LOCATED IN THE MOUNTAIN BASIN
Shukurov I.
professor, doctor of technical sciences, RAASN Advisor Moscow State University of Civil Engineering (MGSU)
Abstract
This article reveals the problems of airing cities located in the mountain basin. The mountain-hollow space is characterized by considerable complexity due to the variety of relief orography with the prevailing calm condition. The problem can be simplified by considering some thermally active surfaces and shapes that are repeated throughout the entire mountain-hollow space. Describes the theoretical data defining the speed depending on the scheme of air along the slope of mountain-relief hollows. It is also calculated wind diagram of the structure of formula slopes and determining the velocity of the air flow along the slope, and the technique of field observations. Practical recommendations to enhance ventilation and normalization of the atmosphere in the city.
Keywords: the problems of airing cities, the mountain basin.
Historically, many cities in the world are located in river valleys or connected with mountains. To them it is possible to carry the following cities and to allocate for them characteristic landscape positions:
• Valleys - Paris, Baghdad, Cairo, Kiev, Moscow, Lower. Novgorod, Yaroslavl, Mesopotamia etc;
• Foothills(npHropHbie) - Istanbul, Shanghai, Tokyo, Mumbai, Rio de Janeiro, Havana, San Francisco, Vladivostok, Sochi, Sevastopol and others;
• Foothills(npegropHbie) - Samarkand, Tashkent, Ashgabat, Alma-Ata, Vladikavkaz, Grozny, Milan, Munich and others;
• Mountain hollow- - Yerevan, Kabul, Tehran, Damascus, Geneva, Sanaa, Bishkek, Dushanbe and others.
Here, we touch on the problems of airing cities located in the mountain basin.
The location of cities at the depth of the mountain basins to 150 m or more and the increase in the intensity of urban infrastructure and economy lead to stagnation of air and an increase in the level of gas contamination, dustiness of the building exceeding the maximum permissible values.
The negative factor in the location of these cities is the decrease in the intensity of natural air exchange, with the help of which the removal of pollutants outside urban areas is carried out.
Consequently, at low wind speeds, it is vital to intensify the ventilation of cities.
Therefore, the solution to the problem of increasing the efficiency of airing should be sought in the way of increasing natural air exchange in the very space of the city.
The microclimate of cities located in mountain-hollow conditions has distinctive features. In the absence or in a small amount of precipitation (particularly rain) or adverse weather conditions there is an additional contamination of the atmosphere. Consequently, managing aerodynamic processes, ensuring ventilation and normalizing the atmosphere of cities by increasing the intensity of natural air exchange is an important task, as well as the main condition in the life of citizens.
Consider the city of Kabul, which is located in typical mountain-hollows relief.
Afghanistan is a country in Central Asia, has no access to the sea. The country is bordered by six countries: Iran in the west, Uzbekistan, Tajikistan, Turkmenistan and the People's Republic of China to the north and Pakistan to the east and south. Its capital is Kabul.
The city of Kabul stands on the river Kabul. Located at an altitude of 1800 meters above sea level. Here, the summer months are exceptionally hot, the winters are cool and rainy. Landscape conditions of the city are complicated by the seismic activity of the region. At the same time, it is located at the bottom of the hollow part of the middle mountainous terrain.
Accounting for the wind regime of residential development in the conditions of the mountain-pithed relief is very actual for Kabul task. Against the backdrop of the positive political processes taking place recently in the Islamic Republic of Afghanistan, the issue is not only the restoration of houses destroyed during the war,
but also the creation of a modern look of the country's capital - Kabul. However, Kabul is located in an area with a hot climate combined with low air mobility, as the city is surrounded on all sides by mountains. The mountains occupy about three quarters of its territory.
The maximum daytime temperature of outdoor air in the summer often reaches + 45-50 ° C. When measured near the earth's surface, heated by the sun, the temperature exceeds 80 ° C. In high-altitude regions in the winter months, the air temperature drops to -30 ° C and lower. The most favorable in terms of temperature conditions are mid-mountain regions, where the average air temperature in summer does not exceed + 25-26 ° C.
The high altitude of 1200-1400 m above sea level determines a noticeable change in the temperature-humidity and radiation regimes in comparison with the foothill areas.
The main components of the microclimate of the city include: air speed, temperature, solar radiation and humidity. Speed, air temperature in the city depends on the speed and temperature of the air on the surface, as well as on the thermal factor, which accelerates the heating or cooling of the airflow.
The maximum value of wind speed is observed in the daytime, with convection, inversion - at night. Relative humidity of air in space, can be less or more than on the surface.
For the reliable protection of the atmosphere from pollution, it is necessary to carry out a set of preventive measures that take into account the climatic conditions on the basis of which the calculation of the city's ventilation.
Thus, a change in these factors in order to improve the natural airing of the city, and thereby reduce the concentration of harmful impurities, although possible, but on a very limited scale.
The composition of the atmosphere also affects the properties of air streams entering the atmosphere of the city.
Studies of the microclimate of Kabul were carried out with the help of statistical analysis of long-term observations in the measurement of wind speed, gradient observations at the "bottom-surface".
With the help of an anemometer, the speed of air movement was measured, the direction of the wind at the highest point and near the Kabul River. The author established that the wind flow along the river has a predominantly western direction - 38%, the northern direction at the surface -33%, the northeast direction - 1622%, with a wind speed of V<2 m / s, the atmosphere of the city is polluted.
Dust content reaches 1.5-50 mg / m3.
Convective air exchange scheme
The thermal regime of the city's atmosphere affects the intensity of contamination by harmful impurities. When heat is transferred by convection, unevenly heated volumes of gases move in space.
Convective air exchange on slopes arises if the vertical temperature gradient is positive and larger than the dry adiabatic temperature gradient. In this scheme, the air exchange on the slopes is carried out by air streams rising along their slopes.
Due to the release of heat from the active surface, solar energy, convective heat exchange is created in the atmosphere. Solar energy is enhanced by the time of day, depending on the location of the building in space
and its parameters. Heated air masses rise to the surface along the slopes of the mountain slopes, capturing harmful substances from the developed space. This
creates a convective ventilation scheme (Figure 1).
Figure 1
mrmmmvm
Convective scheme for ventilating the slope in the floodplain of the river and the city.
The reason for the formation of air currents is the difference in the heating of air on the slopes and at the same height in the free atmosphere. In this case, due to uneven heating of air, a horizontal pressure gradient arises, and in the free atmosphere of the slope the pressure will be greater than on its slopes. Consequently, the warm layers of air adjacent to the heated slopes rise along them, and the upper, less heated layers of air, like the heavier ones, descend downwards, which in turn warm up and, becoming less dense, also rise, and in their place cold layers of air return, etc.
The flow velocities in the convective scheme increase in the direction from the bottom upwards and on the northern side of the slope as more heated are obtained higher than on the southern slope. With a valley depth of up to 100 m-120 m, the flow velocity at the upper edge reaches 1.5 m / s [4].
The average wind speed of the mountain-valley circulation rises from 0 at the slope surface to a maximum at altitude.
Vmax = 0,322 e
1 jgPa2
VB
where Ki, is a coefficient that takes into account the slowing of the air flow due to the influence of the ledges (Ki, = 0.11 at a height of the steps of 10-12 m and slope angles of the slope of 20 ° -30 °); g - acceleration of gravity, m / s2; H- Depth, m;
h - depth of the location of the point from the surface in which the speed of the air flow is determined, m;
tk u tn- respectively, the temperature of the air streams at a point located at a depth h and on the surface of the slope, °C;
/?- slope angle, degree.
where 81 = tk — tn —temperature perturbation; a - turbulent diffusivity coefficient; ft — coefficient of temperature expansion; V - air flow velocity along the slope B = y0y - the difference between the adiabatic and the actual vertical gradient.
Inversion scheme of air exchange As a result of uneven heating of the southern and northern slopes, an inversion-convective scheme for moving the air flow is created. At the same time, on one slope the air goes down, and on the other slope it rises.
In this scheme there can be two cases of air exchange, although they are based on the same physical phenomenon.
The first relates to air exchange on slopes located on the plain or in the valleys, which represent a closed contour (Figure 2In such places, with inversions, the cooled air flows down to the deepest part of all the slopes, as a result of which layers of cool air polluted with dust or gases form on the bottom. In this case, the depth varies in large limits and even can be equal to the depth of the cavity. Velocity streams slope does not exceed 1-1.5 m / sec, and under the level inversii- 0.1 m /
Fig. 2. Inversion scheme of air exchange in the valley of the river Barada
The flow velocities on the slopes of the slope above the inversion layer can roughly be determined by the formula [2].
u =K
Ighsrn p T" Tk
m/c,
Where K- an experimental coefficient that takes into account the decrease in the forces of gravity due to adiabatic heating of the air, the presence of steps and
friction of the flowing airflow about layers of still air (K= 0,35 at slope angles of the slope 25-30°);
h - depth of the location of the point from the surface in which the speed of the air flow is determined, m; Tk, Tn- average absolute air temperature at the surface at a point located at a depth h, 0K.
This case of the inversion scheme of air exchange is most unfavorable, since in this case dust and harmful
impurities accumulate on the slopes and contamination of the general atmosphere, and their removal begins only after filling the trap with cool air to the surface level.
The second case involves air exchange on the slopes located on the slopes of the reliefs (Figure 3). With inversions, such slopes are ventilated by a descending cooled airflow that flows down to the valley
adjacent to the slope, removing from it all harmful impurities.
At the same time, general air pollution or stagnant zones do not arise on slopes. Stream velocities on the slopes of the slope increase from top to bottom and at high values of the vertical gradient of air temperatures, steep angles of slopes and their large extent can reach 4-5 m / s and more than ensure intensive ventilation of the entire slope and individual locations.
Fig. 3. Inversion scheme of air exchange in sloping relief
In this case, the flow velocities on the slopes of the Straight-through circuit airing (Figure 4) is
sides of the slope can also be roughly determined by the characterized by the coincidence of the air velocity vec-above formula. tor at a high mark and in the city itself.
A straight-through ventilation scheme arises at the slope angles of the leeward slope below 15".
Figure 4 - Straight Flow Diagram
Recirculation air exchange scheme
Recirculation scheme air exchange in the valley occurs at wind speeds of more than 0.8-1 m / s and the slope angles of the leeward side ft > 15° or ft < 15° , as a result, a considerable part of them (50% or more) creates conditions for circulation of flows of the reverse direction. Here, the prevailing wind speed exceeds 0.81 m / s and is characterized by the presence of a zone of reverse air currents (Fig. 5).
The air flow moving above the city is constantly expanding, reaching the opposite slope of the mountain, washing its ledges, moving upward, carrying with it harmful impurities near the river of the city, coming in the direction of the wind. In the deep parts of the city after a calm process of ventilation is observed for a very long time. With increasing wind speed and surface dimensions, the ventilation efficiency under this scheme increases.
Figure 5 - Recirculation airing scheme
The airflow in the valleys acquires such a structure when the outer boundary of the boundary layer reaches their windward slope, i.e. in valleys with the ratio of
geometric sizes
Inversion-convective air exchange scheme
If the air of one of the slopes is in the state of radiative cooling and the other is insolated, then conditions arise when the vertical gradient of air temperatures on one of the sides can have a negative value, and
the other is positive and differs in magnitude from the dry adiabatic temperature gradient. In such cases, on the slopes along one side, the air flows down, while in others it moves upward and the air exchange circuit in them is called the inversion-convective (Figure 6). Such conditions in valleys arise during periods of sunset or sunrise and the duration of their action is insignificant. This scheme is inherent in all the shortcomings of the convective and inverting schemes of air exchange on the slopes.
Fig. 6. Inversion-convective air exchange scheme
The velocities of air currents on slopes of slopes do not exceed 1 -1.5 m / s and are minimal in its deep part.
With an inversion-convective scheme, the mass of fixed air at the bottom of the depression is not formed or its height will be negligible.
This scheme, after sunset, goes into the inversion mode, and after sunrise, into the convective air exchange scheme.
Mathematical model of calculation of air exchange in the city
To assess the effectiveness of the above methods of normalizing the atmosphere of the city, it is necessary to study the aerodynamic processes in these climatic conditions. Given the complexity of the task, the most appropriate method of investigation in this case should be considered modeling the distribution of airflow in the city. For cities with a rectangular or close to it layout form, the calculation method is simpler. For cities of complex configuration with poorly ventilated stagnant zones, more reliable data can be obtained by modeling. The data obtained can serve as a basis for calculating the necessary effectiveness of a complex of measures and means for normalizing the airing of the city.
Для прогнозирования расчетным методом или моделированием необходимы следующие сведения:
1) Physical and mechanical properties of urban air;
2) Spatial planning organization of the city;
3) Characteristic profiles of the city;
4) Rose of Wind;
5) Wind direction and repeatability,
6) Humidity, air temperature and active surface, etc. [3].
The application of the modeling method not only builds a model that takes into account the necessary features of the process of distribution of air masses in space, but also imitates simulation. To do this, you must specify the initial and boundary conditions. The solution of this problem will allow calculating the number of stagnant zones and speed values for each city height.
To construct the model, we used the program ANSYS AIM. To improve the performance of natural ventilation, the slope of the river was subject to low-temperature heating. As a heat source, chrome wires. Electric heating was carried out with a voltage of 3545 V. Along the slope, the formation of a heat flux was considered, as a result of which the air exchange increased.
As a result of computer simulation, data were obtained that can serve as a basis for calculating the necessary efficiency of a complex of measures and means for normalizing the composition of air in a city. It will also be possible to determine the number of stagnant zones and the magnitude of the wind flow rates in each territory.
Full-scale research
When processing the data obtained during field studies in Kabul, it was established that in the lower territories there would be a decrease in the wind speed, hence an increase in the volume of stagnant zones, which hinders the process of natural air exchange (Figure 7).
36 AS 60 72 глубина h jpbopa. и
Figure 7 - Velocity of air flow at various depths of the city
The above studies show that the speed of the air flow near the river and its space depends on the value of wind speed at a high point. Therefore, in assessing the intensity of natural ventilation, an analysis of the wind rose should be carried out, which reflects the frequency of repetition of wind currents of different directions. The efficiency of airing is connected with taking into account the prevailing winds in the city.
In 2016, in Kabul, field observations were carried out-measurements of air speed at sites with different altitude marks and at different slope distances. Measurements of air temperature on the surface of areas and in points, the speed of air flow and the relative humidity of air.
It is known that in the immediate vicinity of the slope, the air flow around it is retarded, and strong vortices may appear in it. In hydro-aerodynamics this layer is called the boundary layer. Experimental study of the boundary layer [7] showed that on the very surface of the streamlined body the flow does not move and, as it were, "sticks" to the surface.
In connection with the foregoing, it becomes necessary to determine the dependence of the angle of incidence and the profile of the slope, the velocity and the height of the propagation of a moving jet of air flow, so as to ensure the continuity of the flow from the initial slope to the river.
To solve this problem, we will consider the moving stream in the boundary layer to be laminar, since it is assumed that the slope and the territory near the river are completely washed with a stream of air (without detachment of the jet and formation of large eddies). Such a flow is formed for small values of the Reynolds number (Re < 4,5-105) [9], defined by formula:
where t> - flow velocity for flow around a slope, m / s; l - the height of the laminar flow in the projection on the axis y; v - kinematic viscosity of air, m2 / s (under normal conditions v = 1,45 105).
Flow with number Re occurs within the boundary layer, i.e. within the height of the working zone (1.5 -3 m above the ledges of the slope and the territory near the river).
Thus, the acquisition offers the opportunity to offer practical recommendations for enhancing air exchange and normalizing the atmosphere in the city.
REFERENCES:
1. Krogius V.R. Urban planning on the slopes. Moscow: Stroyizdat, 1988.
2. Retter E.V. Modeling in the study of the microclimate of buildings and their complexes. In: Climatic zoning for the design of dwellings. Moscow: 1969.
3. Shukurov I.S. The problems of the heat and wind regime in Iraq's home. In the book. сб .: "Construction - formation of the environment of life", Moscow, 2008
4. Shukurov IS Use of slopes, slopes and complex relief in landscape design "Akbulak" p. Jam / I.S. Shukurov // Problems of Architecture and Construction. № 3, Samarkand, 2017 p.10-13
5. Shukurov I.S. Ahmed Elamin MA Influence of the Blue and White Nile on the ecologicalecology of the coastal urbanized territories of Khartoum. I.S. Shukurov // ASG. No. 3 2016 pp. 15-19
6. Shukurov I.S. Vertical planning of territories. Fundamentals of computer-aided design. ASV. M .: 2012.- p. 223
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9. Shukurov, I.S. Investigation of the formation of convective airflows in multi-storey residential buildings / I.S. Shukurov // Real Estate: Economics and Management. - М.:, 2015. - № 4 - С. 27-
