Fire-Resistance Mechanism and Residual Bearing Capacity of Prestressed Concrete Beams after Fire Exposure

Abstract

The fire resistance and residual bearing capacity of prestressed concrete (PC) beams after fire exposure are very important to the safety of engineering applications. This study performed experimental investigations and theoretical calculations of the fire resistance of PC T-beams subjected to a standard fire. Effects of fire exposure time, steel strand location, and prestress level on failure mode, ductility, residual bending capacity, and residual stiffness of PC T-beams were investigated. The bending working mechanism of PC T-beams after exposure to the standard fire was determined. With increased fire exposure time, the ductility and bending stiffness decreased significantly and the failure mode changed. However, because of catenary action, extra vertical force between the end support of specimens and steel strands increased the ultimate bending capacity of fire-damaged PC T-beams. Multilayer steel strands with high prestress could delay initial crack occurrence and increase residual bending capacity effectively. However, they have little influence on residual stiffness.