Wu Yongqing Wang Li structure, so the component expansion generates additional stress.
The test results showed that at about 0*C700*C (steel temperature), the thermal expansion of the component increased with the increase in temperature but during the 800C900C period When the component has shortened the phenomenon temperature of more than 900c on the basis of the original extension, it begins to swell, and \”phase transformation\” appears.
at high temperature, the mechanical performance of steel changes.
] At 250C, the strength and elastic modulus of the steel structure did not change much. When exceeding 250C, the \”plastic flow\” steel temperature began to occur more than 300c, the strength and elastic modulus decreased significantly, and the yield stress of about 20C steel was in the yield stress in 20C. It can be reached in about 15 minutes.
Stress changes caused by loads and temperatures. Compared with the reinforced concrete structure and masonry structure, the bullet structure is light, the construction cycle is short, the earthquake resistance performance is good, easy The advantages of industrialized production, low labor intensity, and high recycled utilization rate.
The steel structure has become more extensive with the development of national economy and science and technology. Quickness has also brought some new fire resistance requirements, and the relevant fire protection design specifications are not fine enough in terms of structural fire prevention and component refractory resistance, and lack of fire prevention requirements for the overall structure.
Therefore, it is necessary to be necessary Based on the requirements of architectural fire prevention performance, on the basis of specifications, the fire prevention requirements are comprehensively proposed, the existing conditions are made full use, the overall fire resistance performance of the building is improved, and the fire resistance requirements and structural fire protection measures of the building are consistent. , The requirements for the fire resistance performance of steel structure must not only be checked strictly based on architectural fire prevention design specifications, but also on the basis of specifications, according to their mechanical performance characteristics, specific problems and specific analysis in order to adapt to the current fire development trend of steel structure buildings.
1. The main factors that the steel structure should consider changing structural performance changes in the high temperature of the fire is non -combustible material, but as a structural material, its refractory resistance is not perfect, and it is easy to change in the high temperature state of the fire. , Resulting in structural destruction.
The main factors are when the temperature rises, the steel component should expand.
Because the steel structure is generally a constrained ultra -stable wing edge side, the edge of the edge of the wing edge is stable and stable. , Plastic hinge phenomenon.
Multiple, high -level framework due to the local fire effect of high temperature or underpillar, which causes the beam to extend, bend the deformation, and stabilize the wing edge side. Reduced the column and deformed, causing overall structured damage.
sexual strain, plastic strain, and creep, which has a huge impact on the bearing capacity and integrity of the structure. Vitality passes through radiation and flows to the flowing component, and as a well -guided solid component, the heat conduction inside the steel is very fast, because This structure is easily spread and easily spreads, causing the structure of the structure to be expanded.
The basic function of the structure is to withstand loads. In the fire, as the temperature of the steel structure increases, the carrying capacity will decline, and it will fall to the fall to the fall, and it will fall to the fall to the fall, which will fall to the fall, and it will fall to the lower to the fall, which will fall to the fall, which will fall to the lower to the fall. When the combination effect of the load and the temperature is equal, the structure reaches the limit of the fire load.
The performance of the steel structure needs to fully consider the role of load and structural constraints in order to fully meet the performance during the fire design. Safety requirements, make the structure meet the \”structural fire resistance\” time requirements under the condition of determining the load.
2. The destruction characteristic roof load structure of several major steel structure forms in the fire state. The load -bearing structure connected through the bolt or welding of the pole is better. However, at high temperature, the pole or contact deforms, especially the plastic deformation or swelling, can cause large changes in the structure or even destroy it. [[[[[[[[[ 123]
The application of large space public buildings and industrial plant warehouses is widely used. This structure is composed of steel door frames and connecting it through cables and bars. The profile is connected by the bolt and then connected to the foundation. It is a hinge component, which is an unstable structure. Only the connection supported by the barrier, the cable -holding support, and the connection beam can form a stable structure.
If the door format The connection component of the steel frame reaches the bearing limit under the combination of the load and the high temperature, and the door frame is prone to an accident similar to the \”Domino\” bone card. The fire resistance time of the building is determined by the overall role of these components.
, it belongs to the super -quiet structure, which is easy to generate a large temperature stress under the fire.
High temperature beams and columns are easy to be easily because The changes in stress produce axial strain, creep, and metal roofs on the upper and lower metal roofs are mainly light steel skin.
Construction is simple and widely used.
Due to the characteristics of its structural characteristics, a small fire was removed. Outside, after being high -temperature, the non -protective layer of iron is easy to cause plastic changes due to excessive temperature, which leads to the overall collapse, the fire spreads, and affects the saving and may bring greater economic losses and casualties.
] The steel truss is mainly used as a large span space structure beam.
It has the characteristics of light weight, compact structure, but due to the characteristics of its components, due to high temperature, it is easy to cause temperature stress and cause structural destruction. [123 ]
Destroying characteristics are different as the frame beams and simple branch beams.
3. The main fire protection measures to improve the safety of steel structure fire resistance performance water cooling method.
[ 123] This method has special requirements for structural design and water supply facilities. At present, it is rarely applied.
Single shielding method.
Mainly The fire surface of the steel component sets the fire blocking barrier to separate the component from the flame.
Pour the concrete (generally made into solid protection) or masonry fire resistance bricks.
fully closed the steel component, However, the space occupied is large.
uses refractory light -resistant plate as a fire outsourcing layer (usually a hollow package method).
Use lightweight plates and keels to cover the steel components, mainly used It is more suitable for residential and office buildings.
Apply fireproof coatings (belonging to the construction method).
Construction is simple, light weight, long refractory time, and is not subject to component shape restrictions, economy and economy and economics and economics and economics and economics and economics and economics and economy and economics and economy and economics. Good practicality.
Comprehensive Protection Law.
Comprehensive use of the above measures according to economic and aesthetics. Based on the optimized design, the building automatic fire extinguishing equipment and above protection measures are reasonably set up.
4. The main factors and preventive measures that affect the safety of steel structure fire resistance cannot strictly use the nature of the construction of the steel structure building. The type determines the building fire prevention requirements, so that the requirements are not strict, so that the overall fire resistance performance of the building does not meet the requirements, especially in buildings with complicated functions and uncertain uses, such problems are more prone to occur.
123] Therefore, you should understand the fire resistance level and importance of architecture as well as as much as possible, familiar with the drawings, and properly predict the direction and characteristics of the use, and correctly determine the fire performance requirements.
Improper protection measures, causing inconvenience of construction, so There are protective loopholes, not paying attention to the protection of structural order, or insufficient consideration of cross -construction, the protection of the naked structure part in time.
Therefore, the accuracy and comprehensive technology should be improved in construction management Sex, strengthen the supervision of construction site.
There is no comprehensive demonstration of structural safety performance, and protective measures are taken to ignore the structural performance requirements for the building.
should fully pay attention to the familiarity of structural mechanics characteristics and fire prevention use性能安全要求，采取更为全面和准确的防护措施.
对钢结构防火保护措施不够重视或者不够清楚，造成疏漏.
如对防火涂料的涂刷特点、 The thickness is unfamiliar, causing the protective measures to meet the requirements, which affects the safety of the overall fire resistance of the building.
The construction site supervision is not tightly supervised. The problem of cutting cornering and protective measures.
The adverse effects of the overall destruction of high -temperature flue gas to the steel structure are not good enough.
The characteristics of the building space and the fire load parameters of fire loads. Insufficient analysis of characteristics, affecting the requirements of the entire building fire resistance performance Indeed.
For steel structure buildings with large space, clear use, and small fire loads, proper and key protection, both economy and performance safety requirements, can appropriately relax the fire prevention requirements .
In short, the characteristics of the steel structure determine that its fire resistance safety requirements are more complicated than the concrete structure. The effective extension of the required is very necessary for the safety performance of effective improvement of steel structure buildings.