Structural Stressing State Characteristics for Unbonded Prestressed Concrete Continuous Slabs Under Different Fire Conditions

This paper reveals the general working law of unbonded prestressed concrete (UPC) continuous slabs under different fire conditions by applying the structural stressing state theory. Firstly, the experimental deflection data are transformed into generalized work of force (GWF) values to represent the structural stressing state and the corresponding characteristic parameters. Then, the Mann–Kendall criterion is adopted to detect the mutation points where the characteristic parameter curves show a trend change with increasing temperature. Accordingly, it is verified that the evolutions of stressing state modes also present the corresponding mutation characteristics. The stressing state mutations reveal the linear‐elastic branch (LEB) points, elastoplastic branch (EPB) points, and failure starting (FS) points of the continuous slab's working process, complying with the natural law from quantitative change to qualitative change of a system. Finally, the formula is fitted to calculate the failure loads with a verification, and the existing failure loads were redefined to provide a new and valuable reference for analyzing the working behavior of UPC continuous slabs in fire.