Three steel risks

  Hainan Steel tells you: one hidden - steel buckling instability into two categories: the overall buckling and local buckling. Most of the overall instability caused by local buckling when pressure areas or parts Bending slenderness ratio exceeds the allowable value, it will lose stability. It is affected by a number of objective factors, such as load changes, the initial defect of steel, bearing different situations and so on. Support is often overlooked by designers or construction, which is one of the reasons the overall instability. Lifting due in hanging position is different, a truss or truss rod member may become the force number, causing instability; scaffolding overturning, collapse or deformation mostly because of the link, lack of support caused.
Many important structural change in load that may occur, such as bridges, trusses, hydraulic gate, missile launchers and other multi-use statically indeterminate structure, because it has no unnecessary lever, a lever can be prevented due to instability caused by the overall instability . Another example is the steel beams due to the combination of high and thin web and thin or wide flange can also cause local instability.
In retrospect, we should be wary of is that with the emergence of steel, the instability associated with the occurrence of the accident, so regardless of design or construction, to ensure the structural stability should be engraved in mind.
The second risk - if corrosion is acute instability if corrosion is chronic. Ordinary steel corrosion resistance is poor, especially in the larger humidity, aggressive media environment, will quickly rust corrode, weaken the carrying capacity of the member. For example BOF shop steel roof, the average corrosion rate of 0.10-0.16mm. According to statistics, the annual output of steel per year worldwide 30% to 40% per year due to corrosion and failure, a net loss of about 10%. In our country a reinforced concrete roof truss , wooden frame, steel and wood roof trusses and steel roof trusses and other accident statistics found that steel roof collapse accident occurred accounted for 38.62%, while the lack of maintenance due to corrosion and a large proportion of the reasons.
For just past the exposed steel spray (brush) two anti-rust paint, proved impossible due to the construction of the paint is completely isolated from the air, when in use lack of regular maintenance measures, so this practice effect is not significant. Galvanized, spray aluminum and other negative practices, its cost and effect is not ideal.
In recent years, the metallurgical industry to adopt an appropriate amount of phosphorus in the smelting of copper, chromium and nickel, the formation of corrosion-resistant steel, rust can form a dense layer on the surface, play a role in isolation coverage, after all, a positive approach.
The three risks - poor fire temperature steel, lifting many of its properties with temperature changes, when the temperature reaches 430-540 ℃ between the steel yield point, tensile strength and elastic modulus of the F sharp drop , loss of carrying capacity. Refractory for steel structures necessary maintenance is an important lesson in situ study of vertical steel slump, a "flat cake" effect. This incident shocked the world, which is the direct cause of the fire. Of course, rule out the occurrence of such events, but also involves all aspects in this case. Spray paint or fire sprinkler systems are powerless.
Hainan Steel Summary: fire resistance of a building depends on the fire resistance of building components is good or bad, when the fire broke out in its carrying capacity should be able to continue a certain time, so that people can be safe evacuation, rescue supplies and extinguish the fire. Currently maximize the use of fire-resistant steel steel high-strength steel, such as steel 15MnV is based on 16Mn steel added on the right amount of vanadium (0.04% -0.12%), high-temperature hardness of the steel can be improved. On the other hand it should be efficient anti-corrosion coatings, especially fire anti-corrosion coating unity.