Experimental Research And Theoretical Analysis On Fire-resistance Behaviors Of Precast Concrete Composite Slabs

In recent years, the composite slabs have been widely applied in engineering fie ld, and its mechanica l properties at the nor mal te mperature ha ve been suffic ient ly studied. But t he research of its fire res istance behaviors was very limited yet, especia lly the suggest ions of its fire safety design and post fire restoration were lack of the operabilit y. In this paper, the experime nta l research and theoretical ana lys is of eight full- sized precast concrete composite s labs are carried out to stud y the fire reis istance perfor ma nce. In addit io n, the author conduct finite ele ment ana lys is and numer ica l simulat ion to study the inter na l temperature fie ld and mecha nical properties of the composite slabs under fire. At last, the fire safety design met hod and the suggestion of the post fire restoration are put forward.First ly, t he developme nt history and the present s ituat io n of mecha nical properties at norma l temperature of composite slabs are introduced. And the risk of fire accident and the importance of mechanica l properties of composite s la bs under fire at high te mperature are described. Then t he aut hor expounds the present research status of fire res istance and fire safet y design met hods of concrete structures at ho me and abroad.Eight full- sized precast concrete composite specime ns are tested to study the fire resistance performa nce. The influences of steel types, mortar cover and s imply supported type or cont inuo us type on fire end urance of the composite specime ns were analyzed. The deformat ion characterist ic and dama ge for m of me mbers are invest igated through the experiment. The therma l and mecha nical parameters,such as temperature, defor mat ion and fire res istance, are measured. The influence of var ious factors on the fire resistance and fire endurance of composite slabs are analyzed.Based on the ther ma l perfor mance mode l of concrete and steel, the te mperature fie ld analys is mode l of composite slabs is establis hed by finite ele me nt analys is software ABAQ US. The model is var ified by t he test results. The typ ical temperature fie ld and its distr ibut io n of the co mposite slabs are ana lyzed to study the influence factors, such as heating cur ves, the time of heat ing, the he ight of the section and the thickness of fire protection layer on the temperature distr ibut io n of slabs, which provides a reliab le temprature fie ld data for the mecha nica l property ana lys is of the composite slabs under fire.The ther ma l expans ion coeffie nt, strengt h, elast ic modulus and stress- strain relat ions hip model o f concrete and steel(both prestessed tendons and non-prestressed tendons) are determined. The aut hor conduct finite e leme nt ana lys is to study the fire resistance and fire end urance of t he composite s labs under constant load- rise in temprature by us ing t he finite ele ment ana lys is so ftware ABAQ US. The corretness of the FEA mode l is var ified by the experime nta l resut ls of t his paper and other releva nt experimenta l data. O n the basis of t his, the ma in factors affect ing the fire resistance of composite slabs are analyzed and compared.Fina lly, in order to meet the needs of fire safety design and post fire restoration of composite s labs, different fire end urance class requireme nts of co mposite slabs are put forward, according to the ana lysis results and influence laws of fire endurance factors Based on t he degree of damage caused by the fire, the s maller fire damage compos ite slabs can st ill be used after t he fire by re inforcement a nd repa ir. By tak ing into account the fire temperature, the defor mat ion of t he members, the distr ib ut ion and develop ment of t he cracks, the safet y assessme nt and re inforceme nt design met hod are presented, which can provide effective recomme ndat ions for the treatme nt of the composite slabs after fire.