Response of prestressed concrete beams under combined effects of fire and structural loading

This paper presents results from experimental and numerical studies on the behavior of prestressed concrete (PC) beams under the combined effect of fire and structural loading. Four PC beams were tested under simultaneous application of fire and structural loading. Test variables included fire exposure, load level, concrete strength, and restraint conditions. Data generated from fire tests is used to validate a numerical model developed for evaluating the fire response of PC beams under any specified fire, loading, and restraint conditions. The model accounts for critical factors governing fire response of PC beams including fire-induced restraint forces, cracking and crushing of concrete, spalling, and geometry of beam. Specifically, the model can account for varying fire-induced restraint forces that change with fire exposure duration. Results from validation show that the model can capture the fire response of PC beams with reasonable accuracy in both thermal and structural domains. Data generated from fire tests and numerical studies show that restraint forces developed from constraining thermal expansion of beams produce marginal increases in fire resistance of PC beams.