Statistical Analysis of Fire Accidents of Large Spans and Large Space Buildings

All along, the prevention of fire building collapse and the safety protection of on-site personnel is a complex problem faced by fire fighters. As one of the secondary damages in building fires, the collapse accidents generally have the characteristics of difficult prediction, strong suddenness, and large destructiveness. Once they occur, they will pose a great threat to the life and property of the people and the life safety of the on-site fire-fighting and rescue personnel. In recent years, frequent fires of large-span and large-scale space buildings represented by factories, warehousing, large-scale commercial complexes, and wholesale trade markets have resulted in massive accidental casualties caused by building collapse accidents. Such as: November 3, 2003, Hunan Hengyang Hampshire collapsed building fire accident which caused 20 fire officers and soldiers sacrifice, 15 people were injured; January 2, 2015, Harbin North Fang Nanxun three warehouse fire ceramics market collapse led to 5 Firefighters sacrificed and l4 injured.

1 collapse accident statistics and analysis

1 . 1 accident statistics

In view of the timeliness of online news reports and literature, the survey collected and compiled 33 cases of large-span large-scale space building fire accidents between 1990 and 2016. Although not all of them were included, they reflected to some extent the recent domestic For the general situation of large-span and large-space building fire accidents, see Table 1. ( Note: Due to space limitations, only some typical cases were taken from the original 33 cases ) . Statistics found that the fire collapsed after the accident rate in 2000 to be significantly higher than 2000 years ago. First , economic development has been rapid since the beginning of the 21st century. Large-span and large-scale space buildings represented by corporate factories, warehouses, and shopping malls have been widely used in social production and life, and the extensive fire-fighting development and application model has caused severe fire fighting. Fire accidents occur frequently; Second, the network information is developed, and the accident information is easy to spread and collect.

The investigation found that the fire collapse accidents occurred in the company's factory buildings or warehouses, and there were basically hidden fire hazards in the accident buildings. For example, the fire district was privately transformed, there were no firefighting facilities or the fire facilities were not qualified, the company’s fire management was chaotic, fire awareness was weak, and fire protection was Inadequate supervision of the department. As far as the cause of the fire is concerned, most fires are electrical fires, such as circuit short-circuits and electrical failures.

1 . 2 accident analysis

In order to more fully account for and analyze the accidents of large-span and large-scale space building fires, the 33 cases investigated were respectively elaborated on the functions, materials and structures, collapse forms, and casualties of the buildings.

1 . 2 . 1 Use function of collapsed buildings

The collected cases are classified according to the functional classification of the buildings used, as shown in Table 2 . It can be seen that the probability of a collapse accident occurring in building fires such as factories, workshops and warehouses is much higher than that of other buildings that use functions. The reasons for this are that reinforced concrete or steel frame structures are often used in factories, workshops, and warehouses, and a large amount of raw materials, semi-finished products, or finished products are often stored inside. Most of them are flammable or combustible materials. The fire load is large. In the event of fire, the fire will occur. Rapidly spread and developed into a fierce combustion stage, the resulting high temperatures rapidly deteriorate the performance of building materials and can easily lead to collapse accidents. For example, in 2008, Shenzhen Baoan manhole Jin Shun Plastic Factory "12 · 25" fire, a large number of high-temperature plastic raw materials and products of combustion resulting in overall collapse of reinforced concrete frame factory; 2015 Pudong Arowana logistics and distribution warehousing center "March 18 "Fire Causes Steel Structure and Color Plates

Warehouse deformation collapsed. The survey also found that some large-span, large-space buildings have changed the nature of the buildings without fire approval, increasing the fire load virtually. Such as: In 2004 1O February 5, LG Electronics Co., Ltd. of Guangdong Huizhou City, fire, fire steel plant of the third layer and the first floor outdoor canopy temporary warehouse fire were not handle the audit, inspection procedures, it is illegal structures. The third-tier building warehouse increased the fire load, and the steel structure warehouse collapsed 1 hour after the fire, which brought great difficulties to the fire. A canopy built illegally on both sides of the building occupies the passage of the fire truck, which seriously hinders the fire fighting. The PU foam board used as heat insulation below the canopy is fired and led from the outside to the interior, causing a rapid spread of fire.

Table 11990--2016 typical domestic part of the large span space building fire collapse

Table 2 Statistics by functional classification

It is worth noting that although the probability of fire collapse accidents in commercial and residential buildings is relatively low, once a local collapse occurs, it can easily cause a chain reaction in the building structure and lead to an overall sudden collapse. As a result of the sudden and unpredictable collapse, the trapped people often Major casualties of rescue workers, such as the " 11 · 3 " fire accident at Hengzhou Mansion in Hengyang City, Hunan Province in 2003 , and the " 1 · 2 " fire accident at Harbin Warehouse in 2015 .

1 . 2 . 2 Materials and Structures of Collapsed Buildings

Collected cases are classified according to the building materials and structural forms, as shown in Table 3 . Table 3 shows that most of the large-span large space buildings with fire collapse accidents are mainly reinforced concrete structures and steel structures, followed by composite structures and brick-concrete structures. Among them, the brick-concrete structure is a mixed-structure system composed of brick wall bearing, reinforced concrete beam-column plates, and other components. It is more common in early-old buildings. It is rare nowadays, such as the case of Xianglu mosquito-repellent incense plant in Fujian Province and Shaoxing City in Zhejiang Province. Sanyang flocking plant. In the collapse of the composite structure, the first collapse of the steel structure is predominant, because the fire-resistance of the brick-concrete structure and the reinforced concrete structure is better than that of the steel structure. For example, October 5, 2004 Guangdong LG Electronics (Huizhou) Co., Ltd. plant fire, the plant is a three-storey building, a two-story reinforced concrete structure, steel structure three makeshift warehouse, under fire grill The steel structure warehouse first collapsed. Again, April 7, 2010-Plastic Co., Ltd. Shandong Liaocheng new pretreatment plant fire, the top of the first steel structure collapsed, killing the periphery of two concrete ring beam and solid walls collapsed one after another.

Table 3 Statistics by Structure

In addition, most of the collapsed steel structures in the collected cases were not fireproofed at the beginning, resulting in a reduction in the structural fire resistance limit. If Mengniu Dairy ( Maanshan ) Co., Ltd. caught fire in the all-steel North Cold Storage Building, the original design clearly required that all steel structures including cold storage should be fire-retardantly painted and required to meet the secondary fire rating, while the steel structure of the actual cold storage was not used. Any fire prevention treatment causes the steel structure to collapse rapidly in an extremely short period of time after the fire broke out, causing casualties to the firefighters.

1 . 2 . 3 collapse of the building

According to statistics, there are mainly the following types of building collapse in fire accidents:

(1) The whole collapsed. The fire-and-burning time exceeds the fire-resistant limit of the building structure, and the deterioration of the performance of the building materials causes the bearing capacity to decline, resulting in the collapse of the entire building. Such as: January 1, 2013, when Kiko Co., Ltd. in Hangzhou Friends of the fire, the internal storage of plastic products, alcohol, cardboard boxes, foam and other combustible large number of flammable materials, fire load is very large, steel, at room temperature The whole collapsed under the effect.

(2) Roofs, ceilings or ceilings collapse. The roof, ceiling or ceiling structure is damaged due to the high temperature of the flame. Such as: August 2, 2005, Mengniu (Maanshan) Co., Ltd. North cold fire, steel roof collapsed, killing three soldiers died; November 16, 2014, Shandong Shouguang Longyuan food companies fire, herringbone The collapse of roofs and cranes caused a total of 18 deaths .

(3) The wall collapsed. Walls are subject to collapse due to high temperature expansion or external forces. July 28, 2004, Shaoxing City, Zhejiang Province three sheep flocking plant fire, because flocking afternoon asked the north wall suddenly collapsed, killing one soldier buried pressure sacrifice.

(4) Beams and girders collapsed. The beam or girder collapsed due to the innate design of the building structure or the loss of load-bearing construction materials at high temperatures. Such as: July 7, 2008, Fengxian District of Shanghai Co., Ltd. Lei Sheng Dekui plastic car asked the fire, a 6O Gang-meter long girders collapsed, killing three soldiers on the spot sacrifice.

(5) The floor collapsed. Long overtime and excess load-bearing capacity caused the floor to collapse. Such as: January 2, 2015, north of Harbin Fangnan Xun Pottery market on fire Warehouse 3 floor slab collapsed, causing five firefighters buried pressure sacrifice.

1 . 2 . 4 casualties

Due to the large amount of flammable combustibles in large-span, large-space buildings, especially in factory buildings or workshops, the mobility of personnel is large and fire safety awareness is weak. When a fire occurs, a large amount of toxic and harmful fumes are generated, people are evacuated and escape difficulties, and building collapse can easily cause clusters. Casualty accident. Since the collapsed objects are mostly large and heavy components such as walls, roofs, and crossbars, the probability of death is very high once on-site personnel are buried or confined. Among the statistical cases, the probability of having a casualty was as high as 70% , and the probability of death and injury was 66 . 7 % . Of these, a total of 18 cases of casualties firefighters patients (54.5%), there are firefighters sacrifice cases 16 cases, the probability of casualties in the towel sacrifice was 89%. From this, it can be seen that the collapse of the fire building is a major threat to the life safety of the on-site personnel and firefighters.

2 Discussion

Unlike ordinary buildings, large-span and large-space buildings have a very high probability of collapse accidents in fire due to features such as their own construction materials, structures, and use functions, which can easily cause significant loss of life and property. For a long time, how to predict building collapse in a timely and effective manner and avoid or reduce the resulting disasters is an important problem that plagues all sectors of society. Experts and scholars at home and abroad are carrying out relevant research. The existing research results are mostly concentrated in the case study of building collapse in fires, the causes of collapse, the signs before collapse, and the countermeasures; in addition, there are also researches starting from the perspective of protection, such as development. Throw-type ball reconnaissance instruments, reconnaissance robots and other equipment to replace firemen into internal investigation

Investigate and develop various types of fire extinguishing and smoke evacuation robots to attack and extinguish fires and exhaust heat; develop protective positions for fire fighting positions to prevent collapses and wounds. In addition, it is also recommended to fully consider building fire protection design in building design to improve the fire resistance of structural materials, especially the fire protection design of major load-bearing components or structures. In short, it is necessary to sum up the general laws of such building fire collapse on the basis of adequate statistics and analysis of relevant cases, and to lay a theoretical foundation for further research on the fire protection design and fire disposal techniques and tactics of such buildings.

3 conclusions

Through statistics and analysis of typical cases of large-span and large-space building fire accidents in China in recent years, from the use function, material structure, collapse of the building

Analysis of the level and form, casualties, etc., reached the following conclusions:

(1) The probability of a large-span, large-space building, such as a factory building, a workshop, a warehouse, etc., in the event of a fire collapse is much higher than that of other buildings that use functions;

(2) Large-span and large-space buildings with fire collapse accidents are mostly reinforced concrete structures and steel structures;

(3) Collapsed forms mostly manifest as overall collapse or partial collapse;

(4) The casualty rate of personnel including firefighters caused by collapse accidents is very high. The probability of casualties in this investigation collapse accident is as high as 70 % , among which the probability of casualties of firefighters is over 50 %:

(5) Buildings with collapsed accidents generally have non-standard fire control design or management, and use in violation of regulations.

This article was edited by China Rescue Equipment Network.