Experiment and analysis on mechanical performance of prestressed concrete simply-supported slab after elevated temperature

To research the load-bearing capacity, deflection and effective prestress in steel wire of prestressed concrete (PC) slabs after elevated temperature, experiments on mechanical performance of thirteen unbonded and one bonded PC simply-supported slab after elevated temperature were completed. The section of the slab was divided into strips along its depth according to the distribution of temperature field, and the strain-stress relationship of concrete and steel after elevated temperature were introduced, and then the moment-curve of the PC slab was obtained based on equilibrium equations of force and moment on slab section, therefore, the deflection of slab could be obtained by curve integral of section. The experimental results show that: the prestress losses in stress wire in the PC slab after elevated temperature increases with the rise of the effective prestress at ambient temperature and the heating time. The rate of load-bearing capacity degradation of the PC slab increases with the rise of heating time and load level and the decrease of concrete cover. The rate of load-bearing capacity degradation of bonded PC slab after elevated temperature is larger than that of the unbonded PC slab in the same condition. The residual stress and ultimate stress in unbonded stress wire in the PC slab were obtained by fitting curve of experimental data, and the calculation method for normal section load-bearing capacity of the PC slab was established.