Research On Fire Resistance Of Composite Slabs With Re-entrant Type Decking

Recently,composite slabs with profiled decking has been widely used in civil construction,especially in cases of high-rise builidngs.The importance of fire safety of buildings could never be emphasized more enough,of which fire resistance of structure is a crucial factor.Nevertheless,all the design standards and codes for fire resistance both in China and abroad don't provide relevant rules,particularly in matter of slabs with reentrant type of decking,as current regulations more focus on open type composite slabs.Thus,this thesis put more emphasis on the fire resistance of composite slabs with reentrant profiled sheet(Mainly Encondek),by means of fire-resistance tests,finite element modeling and parametric analysis.As a result,fire-resistant design methods and suggestions were brought up to complement current standards.Detailed content of the paper is as following:(1)Fire-resistance tests of four composite slab specimens with various thickness were conducted.All the slabs survived more than 90 minutes of standard one-side fire condition,all of which obvious distortion can be observed.The temperature on the side exposed in ambient environment rises slowly.Thin slabs reach ‘I'(Insulation)criteria first while the fire-resistant time of thick slabs were determined by deformation limits.(2)CoMPared to open-through decking composite slabs,the temperature of upper flange of re-entrant ones climbs slower,less than 600? after 90 minutes.This thermal feature leads to remaining strength and stiffness of profiled sheeting and improves the fire resistance of the slabs as a whole,which is also validated through FEM analysis by examine the temperature,equivalent strain and stresss development of the numerical model.(3)The accuracy and validation of the finite element modeling were confirmed by coMParison to test results.Thus parametric analysis including loading factor,strength of concrete and steel,thickness of sheeting and slab,fire-resistance of the sheeting were conducted.Unlike composite slabs with open-through decking,parameters of steel(including thick ness,strength and etc.)contribute to the fire resistance of slabs.(4)Design method for fire resistance of composite slabs with re-entrant decking were brough up.A simplified calculation formula was given,proving that this type of slabs have better insulation performance.Design method for fire-resistant time of slabs based on deformation criteria was given,as well as one for slabs with fire-resistant steel sheeting.