Study On Fire Resistance And Bearing Capacity Of Prestressed Concrete Composite Slabs At High Temperature

Building fires are one of the most frequent and most serious major disasters.With the extensive application of prestressed concrete composite plate,people have pay more attention to the study of their fire resistance.Prestressed concrete composite plate is a practical assembly of the whole floor,with the advantages of prefabricated floor and cast-in-place integral floor,namely,the excellent overall stiffness,high seismic performance,simple construction and shorter duration and so on.The prestressed concrete composite plate has been applied to a lot of projects,creating a good social benefits.Therefore,it is important to study the fire resistance of prestressed concrete composite plate.The main work of this paper is as follows:(1)The transient thermal analysis of two prestressed concrete composite plate has been carried out by using ANSYS software.The temperature field of the cross-section of the composite plate has been obtained under different heating time.The heat-structure coupling analysis of the two kinds of composite plate has been carried out.The stress cloud,the strain cloud and the vertical displacement of the two kinds of composite plate have been obtained.The results show that the anti-fire performance of the steel at the bottom of the laminated layer is better than that of the standard composite plate.(2)Based on the principle of equivalent strength of member section,the cross section of reinforced concrete bending member under high temperature is equivalent to the section of reinforced concrete bending member under normal temperature,and the calculation method of two-step model of concrete bending member under high temperature is put forward.The results show that the calculated values of the formulas are in good agreement with the results of ANSYS software analysis.(3)Under the calculation method of the two-step model and taking into account the tension film effect of the plate,the ultimate load of the prestressed concrete composite plate at high temperature is calculated according to the plate balance method and the energy method of the two-way plate.The results show that under the high temperature the calculation results of the energy method are conservative with the calculation method of the plate balance method and have some security redundancy.(4)The energy method is used to design the prestressed concrete composite plate.The methods of determining the ultimate bearing capacity of different plate-type composite plates at different temperatures are put forward and the method of determining the type of prestressed concrete composite plate which should be used in civil buildings under different fire-resistant grades is given.