The Analysis Of Impact On Simply Supported Steel Beam’s Fire Resistance Performance Under Fire In Different Coating Thickness

Steel structure is engineering structure which is formed using structuralelements such as different steel sections and steel plates through welding, rivetingor bolt fastening. Owning to its superiority, it stands out and plays an irreplaceablerole among the numerous building structure types. Its advantages are mainlyreflected in its material uniformity, high reliability, good plasticity and toughness,higher bearing capacity under the same dead weight, easy installation and shortconstruction period, etc. However, due to the physical properties of steel, steelstructure’s ultimate bearing capacity will reduce and it will transform greatly. Soonit will reach its extreme state and tend to damage. At present, domestic andoverseas scholars have done a great deal of research in the problems of fireprevention of steel structure, which includes a lot of fire tests and numericalsimulations of steel structure. More effective measure about fire prevention of steelstructure are desired to seek out through these efforts. So that steel structure will bebetter applied to high-rise and wide-spanning buildings which are suitable to thedevelopment of modern society.This paper uses infinite element method and adopts three different fireproofcoating to imitate the impact that different coating thickness on the simply steelbeam’s fire resistance under fire. The main contents are as follows:(1) According to the research object of this paper(a simply supported steelbeam whose span is eight meters) and based on the standard fire temperature risecurve in the room of ISO-834, firstly, coat the steel beam with an ultrathin layer offireproof coating (the coating thickness should not exceed3mm) and then graduallyincrease the coating thickness to analyze the stress and maximum deflection of thesteel beam and average temperature changes of beam section by making use of theANSYS analysis software. The research result shows that fire resistance period ofthe steel beam is growing slowly, but the growth is not linear and also the growthrate is reducing. Fire resistance period of the steel beam will not increase with the increase of the coating thickness, particularly the coating thickness is between2.5mm and3mm. The limit fire resistance period of fireproof coating for theultrathin coating type can reach nearly2hours.(2) Using ANSYS analysis software, keep the simply supported steel beam(thespan is8m) and standard fire temperature rise curve (standard fire temperature risecurve in the room of ISO-834) unchanged, change the fireproof coating from theultrathin coating type to thin coating type (coating thickness exceeds3mm and lessthan or equals to8mm), coat it on the surface of the simply supported steel beamand then analyze the changes of fir resistance of steel beam in the same way. Theresearch result shows that the fire resistance period of steel beam grows in anon-linear fashion, but firstly increases with the increase of coating thickness andthe growth rate stays gentle when the coating thickness is about7mm. Bycomparison, its total fire resistance period remains unchanged. The limit fireresistance period of fireproof coating for the thin coating type is about2.4hours.(3) Using ANSYS analysis software, keep the simply supported steel beam(thespan is8m) and standard fire temperature rise curve(standard fire temperature risecurve in the room of ISO-834) unchanged, change the fireproof coating from thincoating type to thick coating type (coating thickness exceeds8mm and less than orequals to45mm), coat it on the steel beam and then analyze the changes in the sameway. The research result shows that when coating thickness of the thick fireproofcoating is added up to33mm from9mm, the fire resistance period of steel beamgrows in a linear fashion with the increase of coating thickness. But it remainsalmost the same when the coating thickness is between33mm and45mm. So theconclusion can also be drawn that the fire resistance period of steel beam does notgrow unlimitedly with the continuous increase of thick fireproof coating.(4) It is discovered that certain equivalent substitute relations exist in ultrathincoating type whose coating thickness is between1.5mm and3mm, thin coating typewhose coating thickness is between4mm and6mm and thick coating type whosecoating thickness is between13mm and17mm. Each of the coating which belongsto the three types can be replaced by the other two types under relevant coatingthickness.