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Earthquake prevention and disaster reduction

2018-11-08  |   Editor : houguangbing  

China is one of the countries which suffered the most from earthquake disaster, the serious reasons are following:

(1)Most of the world's earthquakes occur in the oceans, but the main cause of disasters to mankind is the earthquakes that occurred on the mainland. China's land area accounts for only 1/14 of the world. But the mainland earthquake accounts for 1/3 ~ 1/4 of the global continent earthquake, it has the largest number of earthquakes on the continent.

(2)Compared to the United States and Japan, because of economic strength and other factors, the quality of the building in our country is poor, low antiseismic level. Casualties were mainly caused by the collapse of the building. High quality buildings can effectively reduce casualties.

(3)Poor hazard awareness, heavy ideological dependence. It is important to enhance citizens’ awareness of earthquake prevention and disaster reduction, and improve citizens' ability of self and mutual medical aid in earthquake disasters. Japan is also home to the most powerful earthquakes, the biggest difference between China and Japan is the weak consciousness of Chinese citizens.

Earthquake disaster in China is so serious, the task of earthquake prevention and disaster reduction is arduous. China’s earthquake prevention and disaster reduction must take the road of mainly prevention and comprehensive disaster reduction. Prevention should include improving the ability to withstand earthquakes, carry out monitoring and forecasting work scientifically.

Anti-seismic fortification of buildings

(1)Main work and foreign experience

All earthquake disasters are basically caused by insufficient seismic fortification standards, improper design, poor construction, poor operation and maintenance of buildings, and lack of awareness of disaster prevention. Therefore, it is very important to do well in seismic fortification of buildings. Mainly do the following four jobs.

One is to do well the foundation work of seismic fortification.

The second is to improve the supervision of seismic fortification of construction projects. The related competent departments in charge of construction projects, especially major ones, strictly check the site selection, design and construction, taking seismic fortification as an important part of project quality management. For example, seismic safety assessment is carried out for a series of major projects such as the Three Gorges Project, Daya bay nuclear power plant, West-to-East Gas Transmission Project, Qinghai-Tibet Railway and other projects that may cause serious secondary disasters.

Third, key areas under surveillance for the earthquake actively carry out reinforcement work for buildings with weak seismic capacity, so that the seismic capacity is significantly improved.

Fourth, strengthening the guidance of building houses for farmers and the seismic fortification of public facilities in villages and towns.

Earthquake-resistant structure is the most direct and effective way to reduce earthquake losses. From the global survey of major earthquake disasters can be found, more than 95 percent of casualties were caused by damage or collapse of buildings, therefore, it is very important to improve the shock resistance of buildings.

The experience of foreign countries is use for reference to our earthquake prevention work. Japan is also a quake-prone country, due to strong awareness of earthquake prevention and disaster reduction, the seismic performance of Japanese buildings is generally high. Yet as time passed, seismic performance of buildings will decline, therefore, the Japanese also pay great attention to regular〝physical examination〞for the building.

The Japan aseismic structure association is based on the relevant provisions of the « Building reference method », formulated « Standards for the maintenance and management of earthquake-resistant buildings », it is requested that the professional technical personnel registered in the association conduct "physical examination" for the aseismic building. There are four types of physical examination, that is, inspection upon completion, regular inspection, emergency inspection and detailed inspection. In particular, regular inspection is worth mentioning: Technicians in addition to check the anti-seismic layer every year, a comprehensive inspection of the building is carried out after fifth years, tenth years and every 10 years after the completion of the building, the inspections contents include the performance of anti-seismic materials, the presence or absence of objects in the periphery of anti-seismic layers that hinder the horizontal movement of buildings, and the presence or absence of damage to equipment and pipelines.

Public facilities are widely used, , which may lead to heavy casualties if something goes wrong, so Japan pays special attention to regular inspection of public facilities, establish a "regular investigation report system for special buildings". Theatres, cinemas, supermarkets, hospitals, schools, gymnasiums, art galleries and hotels of a certain scale are all special buildings. According to« Building reference method », special buildings need to be inspected regularly by senior architects or professionals recognized by the ministry of land and communications, main contents of inspection include: Whether the foundation of the building land is sinking or not: Whether the structural strength of foundation, column, beam, wall, exterior wall, roof is aging or not: Arrangement, maintenance and management of facilities and places of refuge, etc.

Japanese experts point out, there is no once for all ways to keep buildings anti- seismic behavior, parties concerned need to stick to "regular physical examination" for a long time, pay attention to maintenance management, take timely measures after finding problems. Only in this way, we count on earthquake proof construction can withstand the test of a major earthquake.

Some Iranian earthquake experts believe that, shockproof ability of the building is not only related to macroscopic factors such as the structure and foundation of the building, but also related to micro design factors, such as window glass protection、furnishings of bookshelf and cabinet and design of droplight, etc. , all kinds of factors must be considered in order to minimize the earthquake disaster.

Furthermore, for office buildings, schoolhouses and other places where people are concentrated, Iranian authorities have also formulated some security measures, for example, hanging objects such as decorative furnishings and lamps shall be inspected, fixed and repaired regularly; Do not place heavy or sharp objects on such as file cabinets, etc.; Internal communication systems such as loudspeakers must be effective, facilitate evacuation as soon as possible in the event of a hazard; Firefighting apparatus such as fire extinguishers must be effective, convenient for use in earthquake fire; Maps showing the locations of all buildings and escape routes should be provided.

(2)Building seismic fortification

The seismic performance of buildings in China is not high, " tofukasu" projects caused by cutting corners during construction.The transformation of the original building structure in the decoration of the house is the factor of the collapse of the building,which will increase the casualties and losses of people in earthquake disasters. Perhaps the major earthquakes in recent years sound the alarm for building and decorating houses in China. We should reflect on how many caused by natural disasters and man-made in China's earthquake losses respectively.

The earthquake is the most serious disaster causing casualties and property damage. Therefore, it is very important to strengthen earthquake prevention and disaster reduction and take the following measures. Earthquakes are difficult to predict, and zoning standards are also difficult to unify, but anti-seismic standards can be improved, from planning, design and construction to building quality acceptance. The supervision of a series of links can be upgraded and management can be put in place to reduce the loss of life and property caused by disasters.

The seismic fortification of buildings is a measure to prevent earthquake disasters during the construction of projects.

1)The relationship between building structure and seismic resistance

Steel structure seismic level★★★★★

The steel structure is the main structural material of steel. The steel is characterized by high strength and light weight. Meanwhile, due to the uniformity and obdurability of steel materials, large deformation is possible, which can bear the dynamic load well and have great anti-seismic capability. The cost of steel building is relatively high, and the current application is not very common.

Shear wall structure seismic level★★★★

Shear wall refers to a wall added to a frame structure to resist horizontal shear forces. The horizontal shear force to be resisted by high-rise buildings is mainly caused by earthquake, therefore, shear wall is also called aseismic wall. Shear wall structure is widely used in high-rise buildings (residential buildings with 10 floors and above or buildings with a height of over 24m).

Seismic level of frame structure★★★

A framework consisting of a load-bearing beam column reinforced by reinforced concrete, then use hollow bricks or precast aerated concrete, ceramsite and other lightweight boards as partitions for assembly. Wall is mainly to play the role of enclosure and isolation, as the wall does not bear weight, so it can be made of various light materials.

Masonry structure seismic class★★

"Brick" in brick concrete structure refers to a building material of uniform size, also includes other sizes of special-shaped clay bricks, hollow bricks and so on. 〝Mixing〞refers to the mix of reinforced concrete prepared in a certain proportion by rebar, cement, sand and water, including floor slab, lintel, staircase, balcony. These accessories are combined with brick load-bearing walls, so called masonry structures. The seismic performance of masonry buildings is relatively weak compared with the above three.

Home decoration should also be quakeproof, in the renovation to pay special attention, some places are firmly not to change, or else it will be very dangerous to damage the whole seismic design of the house.

In decorating, it is extremely dangerous to smash down load-bearing wall. A load-bearing wall is a wall supporting the weight of the upper floor, the wall is black on the engineering drawing. If it is knocked off, the whole structure will be destroyed: Making holes in the load-bearing walls can also damage a building's seismic resistance. If you see steel in the wall when you smash it, it's a shear wall, it's not allowed to change. Moreover, you can't change the size of doors and Windows on any wall in your room, expand the original size of doors and Windows or build another door, will also cause local cracks in buildings, which will seriously affect the anti-seismic capability, thus shorten the life of the building.

The wall between room and balcony, has one door one window generally, the wall below the window is called "Additional weight wall", which absolutely immobile. Tear down this wall, will make the bearing capacity of the balcony decline, causing the balcony to fall.

2) Do well in three links of seismic fortification

① Seismic fortification requirements are determined: Formulate block plan、carry out earthquake regionalization、evaluate the safety of earthquake:

② Aseismic design: Design in accordance with seismic fortification requirements and seismic design specifications.

③Aseismic construction:Construction shall be carried out in accordance with the seismic design.

That is to say, establish measures to prevent earthquake disasters in engineering construction, involves the project planning site selection, engineering design and construction, until the whole process of completion acceptance.

Doing well in seismic zoning map

Seismic zoning map is based on seismic intensity or ground motion parameters, land scope is divided into maps with different seismic risk degree or seismic fortification grade. This map is the basis or requirements for seismic fortification of construction projects, it is also an indispensable basic data for national economic construction and land use planning. With the continuous progress of science and technology, zoning map of different periods has different connotations.

Application scope of seismic intensity zoning map or ground motion parameter zoning map: ①Basic data of national economic construction and land use planning: ②Seismic fortification requirements for industrial and civil construction: ③ Formulating the basis for mitigation and prevention of earthquake disasters.

The requirement of zoning map is the minimum standard of seismic fortification for industrial and civil construction, areas with better economic conditions, fortification standard can be appropriately raised to make the house stronger and stronger.

Building house according to the seismic fortification requirements

①Seismic fortification require that construction projects formulated or audited by the seismic department must reach the criteria and technical indicators for resisting earthquake damage.

Seismic fortification requires comprehensive consideration of factors for earthquake environment, importance of the construction project, allowable level of risk, national economic bearing capacity and Security objectives to be achieved.

Aseismic capacity of a house depends on the following three main links.

①Whether houses meet the seismic fortification requirements

②Whether houses have been designed according to the national mandatory standards:

③Whether houses strictly guaranty construction quality according to the standards requirements.

Seismic design code

Aseismic design code is the principles and specific technical requirements for construction projects meeting the requirements of seismic fortification, it is a mandatory technical specification that must be followed in aseismic design. All industries both have aseismic design code, such as railway, transportation, civil aviation, water conservancy, etc.

3)Which places are the dangerous living conditions of towns

①Housing situated under tall buildings or other overhangs:

②Housing under hazardous materials such as high-voltage lines and transformers: During the earthquake, electrical equipment, such as short circuit, easily caught fire, which often endangers housing and personal safety:

③Near dangerous goods producing areas or warehouses.

4)Problems should be pay attention to the rural areas and mountainous areas.

①Vigorously popularize knowledge of building aseismic

②When building a house, choose a safe place first, treat foundation and foundation base. Avoid building houses in areas where landslides, rolling Stones are common and possible: treat foundation and foundation base, make it firm to prevent differential settlement of the house.

③Structural selection of buildings is particularly important. Wenchuan earthquake and other earthquake damage showed that, aseismic capability of soil structure is the weakest, of civil structure and brick- wood structure is also relatively weak. Brick-concrete structure should be pushed in rural residential buildings.

④Reasonable setting and quality of bearing bodies (walls, columns and components) of building structures are the key to the strong and weak aseismic capability of structures. For brick-concrete structure, the brick number, block number, mortar mark, block masonry method and tied steel bar of the load-bearing wall must have sufficient quality assurance. Wall thickness should be at least 240mm. Constructional column is also one of the load-bearing components of the brick concrete structure, and it is the second line of defense for the housing structure, when the load-bearing wall is destroyed, the constructional column can support the superstructure and resist earthquake damage.

⑤Load bearing wall opening hole and window hole should be moderate. Farmers often open the sunny side windows oversize for light, resulting in pier between two windows and wall between windows and doors very narrow, this is not conducive to building aseismic.

⑥Thickness of the non-load bearing partition wall of the house shall be above 180mm, unfavorable use 120 mm. Otherwise, non - load-bearing partition wall collapse easily cause casualties when the earthquake occurred.

⑦Prefabricated slabs should not be used for floorslab and roof panels, cast-in-place reinforced concrete floor slab should be used as far as possible, the latter can greatly improve the overall performance of the structure.

⑧Reduce weight of the structure as much as possible, avoid top-heavy construction, this is conducive to improve the seismic capacity of the structure.

⑨Facade and layout of the house and layout of the rooms should be as regular, uniform, symmetrical and consistent as possible, don't make big mutations. Examples of sudden changes in roof shape and rooms are common in earthquakes, such damage and loss can be avoided in construction.

⑩Money spent on excessive decorate of buildings is used to strengthen the structure's anti-seismic measures.

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