Do steel structure and steel space frame have to do fire protection?

Whether steel structure and steel space frame are painted with fire-retardant coating should be determined according to the fire risk category. The "Code for Fire Protection Design of Buildings" explicitly stipulates that Category D and E are not necessary to be painted, but Category C and above must be. Steel as a building material has some unavoidable defects in fire protection. Its mechanical properties, such as yield point, tensile strength and elastic modulus will drop sharply due to the increase in temperature. Therefore, it is very necessary to make steel space frame and steel structures for fire protection. Steel structures and stainless steel space frame usually lose load-bearing capacity at a temperature of 450 to 650°C, and then they occur great deformation that would result in the bend of columns and beams. This excessive deformation will make the steel unusable. Generally, the fire protection limit of unprotected steel structure is about 15 minutes. The length of this time is also related to the speed at which the component absorbs heat. To make steel structure materials overcome the shortcomings of fire protection in practical applications, it is necessary to carry out fire protection treatment. The purpose is to increase the fire protection to the limit specified in the design code. There are various methods to prevent the deformation and collapse of the steel structure in the fire. The key is to adopt different methods according to different situations, such as using heat insulation and fireproof materials to prevent frame from direct burning, reducing the speed of heat transfer to delay the time of temperature rise and strength weakening. But no matter what method is adopted, the principle is the same.