Post disaster assessment and technology of reinfor

2022-08-13
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Pay attention to the post disaster assessment and technology of reinforced concrete structure fire

once the fire accident is found, it is necessary to enter the site as early as possible to explore the new development of plastic granulator technology, in which general plastic accounts for 350000 tons of Exhibition Road or its surroundings. After the fire is extinguished, the original data should be collected when the site is not damaged

(1) fire time, cause and fire extinguishing method. The fire time and duration of the building shall be recorded in detail. After the fire, there was a development stage from small to large, and then the fire weakened after extinguishing the fire or running out of air and fuel. In the fourth quarter of 2013, the plastic machinery market in the United States had a good trend until it was extinguished. Try to find out the location of the fire source and the cause of the fire, which is of great significance to avoid fire in the future. Different disaster victims have different fire-fighting methods, and the means of fire-fighting should be explained

(2) the process of fire spread and the scope of fire. Starting from the fire source, the scope of over fire is gradually expanded through the combustion of combustibles. Fires often spread to other locations and floors through doors and windows, staircases, aisles, patios, etc. Whether the fire can spread is closely related to the ventilation conditions. Due to the different burning time of each part of the building, the degree of damage also varies greatly

(3) statistics of combustible materials. Especially for industrial and mining enterprises, the varieties, quantities and storage methods of combustibles are different, which should be identified and recorded separately. It is also necessary to explain the combustion status of combustibles after the fire, such as how much is burned and how much remains

(4) degree of structural damage. Reinforced concrete structure is affected by different temperature and time, and there are many kinds of damage conditions. In each fire area, the damage degree of the structure should be investigated separately, such as whether the structure body is intact and the damage degree of the appearance, including the peeling of the protective layer, the exposure of reinforcement, the development of cracks and the deformation of components

(5) evidence collection of on-site materials. Generally, there are all kinds of metal and non-metallic materials at the fire site, such as copper, iron, aluminum, glass, etc., which will undergo different physical and chemical changes when subjected to temperature. Metal drops will be produced at 600 ~ 700 ℃ for aluminum and aluminum alloy, 900 ~ 1000 ℃ for brass, and 1100 ~ 1200 ℃ for cast iron; The glass softens at 700 ℃ and melts at 850 ℃. Obtaining these typical samples in different fire areas plays a great role in the identification of fire

(6) concrete sampling. Concrete is the main material of the structure, and its damage degree has the greatest relationship with the repair of buildings. When the concrete is used to track the problem rectification at high temperature, physical changes and chemical reactions will occur. When the temperature is below 300 ℃, the concrete will not change. With the increase of temperature, cement hydrates (mainly calcium silicate and calcium hydroxide crystals) will change significantly. Clear photos can be taken by scanning electron microscope, combined with X-ray diffraction analysis, which can effectively identify the damage state of concrete under fire

2 technical analysis data of fire

based on the data collected from the field survey, carry out comprehensive analysis and make technical judgments and assessments. These technical analysis data mainly include:

(1) structure fire temperature. It can be comprehensively analyzed according to the following conditions:

the change of concrete surface color is related to temperature: the color below 300 ℃ remains unchanged, 300 ~ 600 ℃ turns pink to red, 600 ~ 950 ℃ turns gray white to light yellow, and greater than 950 ℃ turns gray yellow; Evidence collection of on-site materials (see above);  component appearance: there is no significant change below 300 ℃, the surface cracks at 300 ~ 600 ℃, the quartz aggregate bursts, the concrete at 600 ~ 900 ℃ peels off and shells, separates after tapping, part of the reinforcement is exposed, the surface is loose, the surface above 900 ℃ is powdery, and melts at 1200 ℃; Scanning electron microscope and X-ray diffraction analysis; Carbonation depth detection: normal carbonation of concrete usually occurs on the surface, and carbonation caused by fire can occur inside. The carbonization depth can be used to detect the surface temperature under fire

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