Stressing state analysis of unbonded prestressed concrete simply supported slabs in fire

This paper reveals the essential stressing state characteristics of unbonded prestressed concrete (UPC) simply supported slabs in fire by exploring the experimental data based on structural stressing state theory. First, the experimental deflections are transformed into the generalized work of force values to represent the structural characteristic parameter. Then, the Mann-Kendall criterion detects the mutation points where the characteristic parameter curve shows a trend change with the rising temperature. Next, the mutation characteristics are verified by studying the stressing state modes and coordinative working behavior of simply supported slabs under characteristic temperatures. Consequently, the elastoplastic branch points and failure starting point of the simply supported slabs in fire are revealed, complying with the natural law from quantitative change to qualitative change. 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 simply supported slabs in fire.