According to its thickness, fire retardant coatings for steel structure can be divided into three categories: thick coating fire retardant coatings for steel structure in Province, thin coating fire retardant coatings for steel structure and ultra thin fire retardant coatings for steel structure.The thickness of thick steel structure fire retardant coating is 8-50mm, the thickness of thin steel structure fire retardant coating is 3-7mm, and the thickness of ultra-thin steel structure fire retardant coating is not more than 3mm. According to the national regulations, the fire-proof coating for thin steel structure shall reach 2.5 hours, the fire-proof coating for thick steel structure shall reach more than 3.0 hours, and the fire-proof coating for ultra-thin steel structure shall reach the fire-proof limit of structure. The operation time should be less than 2 hours.The thick steel structure fire retardant coating is not good for decoration, and the thin steel structure fire retardant coating has a certain decorative effect. Its decorative performance is better than that of the thick steel structure fire retardant coating, which is not as good as that of the ultra-thin steel structure fire retardant coating and ultra-thin steel building fire retardant coating.

Fire protection principle of thick steel structure fire retardant coating

Thick steel structure fire retardant coating is also called non expansion fire retardant coating. Its main component is inorganic thermal insulation material. The surface is granular, with small density, and the coating does not expand under heat. Because of its good thermal insulation, it is also called t thermal insulation fire retardant coating.The fire protection mechanism is to use the inherent good insulation coating to prevent the steel from being hot, to form a dense glaze under high temperature, which can effectively isolate oxygen and reflect heat, delay the temperature rise of Guiyang steel structure, and play a role in fire protection.

Fire protection principle of fire retardant coating for thin steel structure

Thin and ultra thin fire retardant coatings for steel structure, also known as intumescent fire retardant coatings, are mainly composed of base material, dehydrating agent, carburizing agent and foaming agent.When the temperature rises to a certain extent, dehydrating agents and polyhydroxy compounds promote the dehydration and carbonization. Under the action of a large amount of gas released by the decomposition of foaming agent, the coating expands.The expansion ratio can be more than ten times or even dozens of times, forming a dense foam carbonized insulation layer, thereby preventing heat from transmitting to the steel structure and playing the role of fire prevention.

Connection design method of steel structure members: practical design method, accurate calculation design method, commonly used simplified design method and equal strength connection design method.

The actual design method is based on the equal strength condition of the net cross-section area of the flange connection.In addition to the shear force acting at the connection location, both ends of the network connection shall be measured by the shear force of each member whose net span is 1 / 2 of the net section area of the web or the sum of bending moments.of course.Accurate design and calculation method, the section bending moment of the flange and web part of the connecting member is propagated through the network according to the proportion of the moment of inertia and the shear force.The common simplified design method is the splicing design of flange bearing all bending moment and web bearing all shear force.

Based on the equal strength design method, the net cross-section area of the joint flange or web splicing with equal strength conditions.The design principle of seismic joint is not only to reduce stress concentration and facilitate processing and installation, but also to meet the principle of “strong joint and weak component”, so as to avoid the damage of the whole structure caused by weak connection.The purpose of the equal strength connection design method is to make the member bearing capacity equal to or higher than the member.Therefore, the equal strength connection design method is often used in the splicing design of structures, which has good continuity and ductility according to seismic design or elastic-plastic design.