The Experimental Research And Theoretical Analysis Of Fire-Resistance Behaviors Of Unbonded Prestressed Concrete Flat Beams

In recent years, the prestressed concrete technology has been developed and widely applied in engineering field, but its using safety which arouse people's recognition increasingly, especially its fire-resistance behaviors have not been perfected. In this paper, based on unbonded prestressed concrete flat beams being as research objects, the properties under fire and behaviors after fire of unbonded prestressed concrete structures have been studied in the tests, and its fire-resistance behaviors are analyzed and discussed with the method of theoretical analysis and numerical calculation together. The main contents include:(1)The capabilities of new grade â…¢ steel bars after fire are studied by experiment. The laws and the calculation expressions of its behaviors after enduring different fire temperatures are obtained, and the calculation formula of the tensile stress-strain curves of new grade â…¢ steel bars after fire are established in the paper.(2)On the basis of traditional heating-conduct theoretical, the nonlinear transit temperature distribution of reinforced and concrete structures are analyzed and calculated. An analytical solution to solve its temperature distribution of one dimension is proposed, and the formula is educed and calculated. Also, its temperature distribution of two dimensions is analyzed through finite element method and the computing program is completed.(3)The experiments of 26 unbonded prestressed concrete flat beams under fire are accomplished in the large structures electrical heating furnace that is manufactured independently. The deformation characteristic and damage form of members and stress varieties of prestressed wires are investigated through the tests. The influences for its fire-resistance behaviors of different factors, which are constant loads, thickness of concrete covers and integrative reinforcement ratio, are researched and discussed.(4)The tests of unbonded prestressed concrete flat beams under loads after fire have been carried out. The macroscopical phenomena, damage features and deformation rules of the members after fire are studied, and...