The Numerical Analysis Of Temperature Field And Mechanical Properties For Prestressed Concrete Slab At High Temperature (in Fire)

It is a long term and arduous task to prevent and control fire. As reinforced prestressed concrete structure is a new kind of modern structural styles in structure engineering , its investigation in temperature field has become more and more significant . It is not only difficult to situate the fire field in the laboratory but also in a considerable risk as well as human and financial resources consuming. This thesis aims to demonstrate finite element numerical simulation study about temperature-stress field of reinforced prestressed concrete slabs under permanent loads when it is in high-temperature conditions .The primary tasks are as follows:(1)The laws of parameters about reinforcing steel and concrete along with temperature at home and abroad are summarized .The finite equations of section temperature field under fire are derived on the basis of the heat conduction fundamental equations in detail .The theoretical foundations of the temperature field software are laid firmly.(2)Based on the last data, the values of convection heat transfer coefficient, radiation emissivity coefficient, thermal conductivity and specific heat of concrete are determinate by a trial and error procedure. After deriving suitable parameters,the temperature field of reinforced prestressed concrete slabs has been analyzed : in addition to that,the ultimate be bearing capacity has been calculated. By simulating the scene of a fire temperature according the ISO standard temperature elevation curve. Temperature change analysis of prestressed concrete simple slab subjected to fire is carried out by using of ANSYS software. Different temperature curves that are apart from the fire surface have been presented in this thesis. Then error analysis has been done by comparing the finite element simulation value with the experimental observed value. The rationality of the finite element simulation value has been analyzed.(3)When the fire,besides its ability to sustain normal use loads,each component of building is also required to sustain extra temperature stress. As a result of border restrictions,the whole reinforced prestressed concrete structures will be deformed by the temperature stress in addition to that, a great internal force will be produced. In this thesis,temperature stress and differential deflection equation of the thin slab interior will be derived from numerical calculation; the finite element software has been used to simulated temperature stress and the deformation and strain of thin slab interior by the non-linear theory. Then besides, the nonlinear analyses were also done on the deflections of the prestressed concrete bonded simply supported slab respectively in ISO standard temperature rise conditions, and the results show that the prestressed concrete bonded simply supported slab has a good fire resistance under the normal design load level.