What are the details of National Technical Regulation QCVN 02:2022/BXD on natural physical and climatic data for construction? What are the data on Vietnam's climate characteristics used in the construction sector?
What are the details of National Technical Regulation QCVN 02:2022/BXD on natural physical and climatic data for construction of Vietnam?
Pursuant to National Technical Regulation QCVN 02:2022/BXD issued together with Circular 02/2022/TT-BXD on natural physical and climatic data for construction as follows:
Accordingly, National Technical Regulation QCVN 02:2022/BXD on natural physical and climatic data for construction of Vietnam applies to the formulation, appraisal and approval of construction activities, including construction planning, construction investment projects, construction design, construction of works, supervision of the construction of works, management of construction investment projects in Vietnam.
- In some separate cases, it is permissible to use wind, earthquake and other natural physical and climatic data for construction provided by competent state agencies such as:
+ Institute of Hydrology and Meteorology Science and Climate Change or the General Department of Meteorology and Hydrology - Ministry of Natural Resources and Environment, Institute of Geophysics - Vietnam Academy of Science and Technology ... for some specific works when there is evidence; it is required to clearly specify the scientific basis of the applicable data and send it to the Ministry of Construction.
What are the data on Vietnam's climate characteristics used in the construction sector?
Pursuant to Section 2, National Technical Regulation QCVN 02:2022/BXD promulgated together with Circular 02/2022/TT-BXD stipulating data on Vietnam's climate characteristics used in the construction sector as follows:
(1) Regarding the climatic season
Vietnam belongs to the tropical humid climate zone, monsoon. The territory of Vietnam is divided into 2 regions which are North and South with different climates:
- The North (from 16 degrees north latitude, level with Hai Van Pass, back to the north): There are cold winters. The cold month plains have an average temperature between 10 ºC and 15 ºC.
- South (from 16 degrees north latitude, level with Hai Van Pass, back south): No cold winters. The plains are hot all year round and divided into 2 distinct seasons: the rainy season and the dry season. The rainy season is from May to October, the dry season is from November to April 4.
(2) Regarding sunshine, air temperature, solar radiation
- Sunny: Throughout the territory, periods of sunshine are long. Average hours of sunshine in a year: The North is less than 2 000 h, the South is greater than 2 000 h.
- Air temperature: The North has a common average annual temperature below 24 ºC; the South has a common average annual temperature between 24 ºC and 28 ºC.
- Solar radiation: Abundant amount of radiation. The average annual total radiation in the North is greater than 586 kJ/cm2; in the South less than 586 kJ/c m2.
(3) Regarding air humidity and weather seasons
Throughout the territory, the relative humidity of the air all year round is high: from 76 % to 88 %. In some places, during certain periods of time, there may be large changes in air humidity due to the influence of some special weather phenomena.
- Drizzly, cold, and humid period: In the North, in the period of winter monsoon (Northeast monsoon) there is often wet drizzle, and the relative humidity of the air is high, sometimes saturated. However, there are times when there is a northeast monsoon accompanied by dry weather with low humidity that occurs over a few days to weeks.
- Humid weather: In the eastern region of the North and the Central coast, in the late winter, and early spring (from February to April) there is often humid weather, the air has a temperature of 20 ºC to 25 ºC and very large relative humidity, over 95 %, at times saturated.
- Hot and dry weather: In the low-lying areas east of the Annamite Mountains and the valleys of the Northwest, in summer, there are hot dry winds blowing in the west, northwest, and southwest directions with an active time from 10 days to 30 days a year.
The weather becomes hot and dry, the temperature is above 35 ºC and the relative humidity is below 55%.
(4) Regarding rain and snow
Throughout the territory, the annual rainfall and duration of precipitation are relatively large, averaging from 1 100 mm to 4 800 mm and from 100 days to 223 days. Rain is unevenly distributed and concentrated in the rainy months. Many rains of great intensity, many continuous and prolonged rains, causing floods.
There is no snow throughout the territory except for a couple of times a year and in a few high northern mountains.
(5) Regarding climatic constructional zoning
The territory of Vietnam is divided into 7 climatic constructional zones:
- Northwest Region (Zone I);
- Midlands - mountainous regions of North and North East (Zone II);
- Northern Plains (Zone III);
- North Central Region (Zone IV);
- South Central Region (Zone V);
- Central Highlands (Zone VI);
- Southern Region (Zone VII).
Note: This is a miniature version of the 1:1,000,000 scale map prepared and provided by the Institute of Hydrology and Meteorology Science and Climate Change - Ministry of Natural Resources and Environment.
What are the characteristics of climatic constructional zones in Vietnam?
In subsection 2.5 Section 2, National Technical Regulation QCVN 02:2022/BXD promulgated together with Circular 02/2022/TT-BXD, characteristics of climatic constructional zones in Vietnam are specified as follows:
- Zone I - Northwest Region: Separated by the Hoang Lien Son Mountains with the boundary line located on the eastern slope along the isovalent line of the heat balance index CCN1,I = -350 cal/min (referred to as the isovalent line CCN1,I). This mountain range is also the boundary dividing the influence of "dry cold" weather and "humid weather" of the spring period between the 2 mountainous regions of Tonkin. Due to the different influences of these 2 phenomena, it has led to differences in the level of heat and cold over a long period of the first half of the year. These are factors that have a certain impact on architectural solutions. However, due to the high average elevation, the basic climatic feature of this region is still a region with cold winters with a predominant anti-cold solution. This is a region where all 3 climate belts simultaneously exist according to altitude. The climate of the Northwest mountains is limited to the south by the mountains of western Hoa Binh province, which, due to the direct impact of the extreme air after crossing the Tonkin Plain over much of Hoa Binh province, has brought into here the basic characteristics of the climate of the eastern region and the Northern plains with the existence of the "humid pot" season and low temperatures in winter.
- Zone II - Midlands - mountainous regions of North and North East: This is the region east of Hoang Lien Son, separated by the isovalent line CCN1,I = -350 cal/min combined with the isovalent line CCNVII = 600 cal/min. This is the region with the coldest winters compared to the whole country, despite the fact that there are still very low temperatures in the high mountains of the Northwest, but at the same altitude the temperature in this region is significantly higher. On the same high belt, anti-cold measures in the Northeast are most important. As a mountainous area, the climate strongly differentiates according to terrain elevation, in the region there exist all 3 climate belts.
- Zone III - Northern Plains: This is a region with worse winter cold levels than the Northeast but higher than the Northwest and North Central regions. It is bounded by the isovalent lines CCN1,I = -350 cal/min and ∆CCNfive = 1,000 cal/min to the north and west. It is separated from the North Central by the influence of hot dry weather due to the influence of hot dry westerly winds (Lao wind), delimited by the equivalent humid heat index CSAIV-VII greater than 2 and CSAVII greater than 2, the number of "hot dry" days all year less than 10. This is a region with hot and humid summers but almost no influence of hot dry westerly winds. Throughout the region, the climate is quite homogeneous, strongly influenced by typhoons and other features of the sea.
- Zone IV - North Central Region: Bounded to the south by the regional boundary, characterized by a gradual decrease in winter cold levels, strongly influenced by hot dry weather during the spring-summer period. This is a region with significant differences in rainy and humid seasons compared to the Northern Plains, CSAIV-VII is less than 2 and CSAVII is less than 2. The terrain is heterogeneous, there exists both the influence of terrain elevation, mainly the low mountain climate belt and a small part of the middle mountain climate belt. Most of this part is located in the eastern part of the Annamite Mountains, catching the northeast monsoon and sea breeze, but there are also some valley and low mountain areas hidden behind higher massifs in the east, so there are some characteristics of the western climate such as the westernmost area of Thanh Hoa, Nghe An, Quang Tri, Thua Thien Hue. The North Central region is the region most affected by hot dry westerly winds from April to September every year, causing extreme dry and hot weather conditions. During the period of hot dry westerly wind activity, the lowest humidity can be down to 30% and the highest temperature can reach 43 ºC. On the contrary, in the last months of the year (from October to December), due to the influence of the northeast monsoon and turbulence at sea, This area often experiences heavy rain.
- Zone V - South Central Region: Separated from the Southern Plain mainly due to the impact of hot and dry weather, on the basis of moisture indicators (CSA > 2) and the number of days with hot and dry weather (NKN > 10). The climate in this region is not really homogeneous, there is a division according to altitude. The majority of mountain areas belong to the low mountain climate belt, a small part belongs to the middle mountain belt, and all of them are located on the eastern face. The western boundary is mainly based on CCN1.0= 0 cal/min and the southern part is the demarcation line on the influence of hot dry westerly winds (the number of hot dry days caused by Lao winds is greater than 10 days). As the area demarcates the difference of the rainy season, the humidity level is due to different consequences of the Southwest monsoon. This boundary line is located between the 2 provinces of Ninh Thuan and Binh Thuan, almost completely separating Binh Thuan into the Southern climate zone.
- Zone VI - Central Highlands: Separated by isovalent lines ∆CCNfive = 700 cal/min, CCN1,I = 0. The air is tropical in winter but still has relatively cold winters over many areas (CCNI < 0 cal/min, CCN1,I < 0 cal/min) due to the influence of terrain elevation. In the Central Highlands, there is no significant difference in the level of cold in winter, but the difference between the cold season and the hot season is very small, i.e. there is only one heat season every year. As a mountainous region, the Central Highlands also exists all 3 climate belts with wide plateaus with a fairly homogeneous climate according to the characteristics of the corresponding high belts. Due to the western slope, the Central Highlands does not have the influence of "Lao winds" that cause hot and dry weather.
- Zone VII - Southern Region: Separated from the above 2 regions by the southern boundary line of the Central Highlands and South Central coastal climatic zones. This is a region with a fairly homogeneous climate, bearing typical features of a tropical monsoon climate. Heat protection is the most important object in preventive solutions for construction works.
Particularly for the sea areas, graft the islands into climates that have been divided on land with similar climatic conditions.
Islands located north of latitude 20.83oN graft into the Northeast climate zone.
The islands between upper latitude and latitude 16.83°N join the Northern Plain or North Central climatic zone.
The islands south of latitude 16.83°N join the Southern Plain climate zone.
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