【 Weak current college 】 building fire safety requirements of steel Member---Power By 【 China power house network 】

September 11, 2001, is located in the United States New York City Center of World Trade Center attacks by terrorists, has suffered two airliner crash, just over 20 minutes, the skyscraper will come tumbling down, causing thousands of casualties. World Trade Center is the symbol of the economic prosperity of the United States, why such a huge building, the building is so weak, the experts, but one is in the affirmative, that is, and the building's steel structure has a lot to do. First of all steel components subjected to violent impact, resulting in fire protection layer of loose, followed by a large number of leaks of aviation fuel in internal combustion caused heavy construction building temperature has risen dramatically, in high-temperature, no protective layer of steel components quickly lose strength and load bearing capacity, eventually put on World Trade Center at naught the tragedies of the moment.

In recent years, with the increasing rate of economic development, in order to shorten the building of the construction period and reduce the cost of construction, steel structure is widely applied to civil and industrial buildings, parts of the old town in the economic development zone, building and reconstruction process, to steel structure as the main component of architectural buildings ratio is constantly on the rise, the architectural design fire protection standard (hereinafter buildings》), the senior civil building design fire protection standard (hereinafter referred to as the "regulations") provides various types of building fire resistance ratings and fire resistance by major component, but also on the fire risk smaller steel structure made of a different degree of relaxation.

«Ò» ¡ ¢ temperature on properties of steel products
Steel is often used in building materials, in ordinary steel structure with a light weight, high strength, particularly tensile, shear capacity and excellent characteristics, thus becoming the main steel structure of the building structure. Steel is a material that does not burn, but a good conductor of heat, heat conduction is extremely easy. Steel in temperatures above 300 ° c, yield and ultimate strength sharply declined, reaching 600 ℃ intensity almost equal to zero. Scientific experiments and instance that unprotected steel structure in fire situations, simply 0.25 hours, its temperature goes up to 540 ° c above, the widget itself, lead to distortion of buildings collapsed destroying, deformation of steel structure also cannot be repaired.

Therefore the building with steel structure if not for fire protection, fire resistance, will have a direct impact on the entire building fire resistance time to internal personnel evacuation and fire fighters fight at risk.
Second, the steel structure of fire protection
The fire protection of steel structures typically have the following ways:
1. fire retardant coatings for steel structures
Fire retardant coatings for steel structures is Shi tuyu on buildings and structures of a steel structure surface, can form refractory and insulating protective layer, to improve the fire resistance of steel structure of the coating, divided into thick, thin, thin, and so on. Thick paint grainy, coating thickness is usually more than 8 mm, construction method for spraying, high temperature is dependent on the thickness of the coating itself and the low thermal conductivity of the insulating steel components. Thin and ultra-thin coatings thinner, have a decorative effect, construction method can be sprayed when it can brush, hot coating swelling thickening protection steel components.

Layer 2, outsourcing
Using in-situ concrete for outsourcing layer, you can cast steel structure, or spraying method (Jet technology). Cast concrete outsourcing layer typically available wire mesh or reinforced to enhance, to limit the shrinkage cracks and guarantee the intensity of the shell. Also at the construction site will surface coated foam steel structure to form a protective layer of mortar. Mortar can be lime, cement or plaster mortar can also be mixed with perlite or asbestos.

Outsourcing layer can also be used Pearlite, asbestos or asbestos-cement, plaster and made of light concrete, precast slab using adhesives and nail or bolt fixed on the steel structure.
3. water filling (jacket)

In hollow steel components in sufficient water is protected from fire, the most effective methods of making steel structure in fire at low temperature. Water circulation inside the structure components, heating of water can be recycled by cooling or by tube into the cool water to replace the heating of water. This method in a foreign country is widely used in steel pole protection.

4. shielding
The steel structure surrounded by refractory composition of wall or ceiling, or will of steel Member concealed in two pieces of wall voids between, as long as the increase slightly increased refractories do not even reach the purpose of the fire, so this is the most economic method of fire.

3. building the widget's fire protection
1. non-bearing exterior walls
Non-bearing exterior walls of the building envelope components, the main role is to protect against wind, rain, snow, heat, noise, etc., in order to achieve the thermal insulation, thermal insulation, sound insulation and fire effects. Industrial architecture and simple building use sandwich color steel plate and other lightweight materials for this widget. Because non-load bearing and is not controlled by shear, such as external force, the force of gravity for itself, the relative force of columns, beams, etc. in the high temperature for a long time to preserve its integrity, prevent the spread of the fire directly. A CPI and senior Treasury more because of internal fuel, fire risk considerably, with explosion hazard, and therefore its non-bearing exterior walls have strong ability of fire, should not be using sandwich color steel plate, other industrial architecture and simple building can take no protective layer of the filling color steel plate. It should be noted that internal color steel plate sandwich fillings should be non-burning material, otherwise the fire, will result in material flow combustion, generate a lot of toxic fumes. In addition, some country fair, using simple greenhouse structures, retaining elements, in the event of a fire can easily interact, burning even camp. The author recommends that fire rectification and own transformation process, increase the sandwich color steel plate, retaining elements, otherwise, the building's fire greenhouse should be spaced to factory, warehouse space tight control for standard.

2, load-bearing pillars, beams, floor
Load-bearing pillars, beams and slabs under construction of vertical load and horizontal load is the main building's stress component, single and multiple layers of industrial buildings and high-rise buildings to reduce cost reductionShort duration or to reduce weight, use this form. And steel components subjected to high temperature will happen after the strength and yield point decline caused building collapse in a short period of time, thus a serious threat to the building of internal staff and the Suppression of the firefighters ' lives, like the World Trade Center collapse of tragic moment like a curtain, so this type of steel components should be the focus of fire protection. Three-level architecture of refractory grade of this widget in particular steel components of the connection point shall strictly for fire protection. 2 fire resistance rating of Ding "factory warehouse due to fewer internal fuel, fire danger is relatively small, post and beam can be unprotected layers of metallic components, but use a, b, c of part of liquids or gases, high-impact, fire protection measures should be taken. For markets, galleries and other large buildings, it is recommended to take concrete or steel column with clay brick package method for protection. Currently the city appeared more merchandise retail housing, landlord for a large indoor space, decoration process are often combined with increased received attic area, some attic area, personnel, and attic ceiling has more electrical lines, such as the use of wood components, it is easy to result in fire, causing casualties and property damage, fire-retardant treatments are recommended after the fire resistance of steel structures, in accordance with the corresponding construction floor and supporting the standard single-layer of the column.

3, roof load bearing members
The roof is located at the top of the House, a barrier and rain and cold maintenance withstand heat, mainly by the roof (insulation) and roof load bearing members, load bearing members mainly under all load on the roof, weight and other loads imposed on the roof, and to support its walls or columns, on the whole, the smaller the load, the higher the position. To storey larger buildings to collapse due to high temperature. Buildings》 was on the roof-bearing structure gives the corresponding fire resistance, but also made the maximum relaxation, secondary fire resistance rating building roof load bearing members except a, b, c liquid or combustible gas flame burns to the site, may not take fire protection. The author believes that buildings》 Regulation placed too wide for firefighters in the process of entering the Interior lives are roof fall from harm occurred from time to time, recommendations on indoor fuel more buildings for fire protection roof load bearing members. The doctrine of "skyscraper requires a relatively high, as long as the steel roof should be fire protection, even the other's ceiling, plastic plates, insulation materials are presented by not burning material requirements, just not on the roof will be 1 hour fire resistance to relax to 0.5 hours, but still need fire protection. For the high-rise building podium, the doctrine of similar widget "is not clear, according to the podium fire partitions and other related requirements, I think that you can reference the buildings》 related regulations. Here I must mention about the firewall, when ordinary building roof for fire resistance 0.5 hours of non-combustion, senior industrial building roof for fire resistance of not less than 1 hour of non-combustion, the firewall may block until the bottom of the roof, grass-roots level is not high out of the roof, but if the roof is not fire protection of steel roof truss, the firewall should be higher than its roof is not lower than 40 cm.

4, staircases
Staircase is building up layer between the evacuation facilities for reinforced concrete structures. 2001 buildings》, the resistance of the law on song and dance Entertainment Entertainment show site to the relevant provisions are adjusted, resulting in many places additional indoor and outdoor staircases, because of renovation, much to the summary of the main steel stairs for the form. Outdoor staircases steel structure because it is located in the outdoor, not vulnerable to the heat of the fire, there is no need for protection, but on the exit of each level, and building the platform to be fire when the effects of heat, must have a fire resistance (1 hour), should be fire-retardant treatments (such as steel structure), ensure that landings allow sufficient time for internal personnel from this evacuation or fire personnel here to fight the fire site. As for the interior staircase for steel structure, with its more vulnerable to fire, should a fire resistance requirements for fire protection processing, supporting staircase steel columns use clay bricks or concrete parcels of protection.