Analytical investigation of vehicle fires in precast concrete parking structures

Abstract

In this paper, the authors examine the effect of vehicle fire loads (temperature and heat flux histories) in precast concrete parking structures. Using a computational fluid dynamics program, analyses were conducted, using such variables as structure geometry and fire characteristics. Heat flux histories were used as input to finite element analyses to determine temperature rise in the prestressing strand of double-tee floor members. Estimates of reduction of steel strength were derived using the increased prestressing steel temperatures. Nine fire scenarios were considered; within them, vehicle fires were found to cause only minor reductions (maximum of 15%) in the strength of the prestressing steel of double-tee floor members. The authors concluded that the geometry of a precast concrete parking structure can have a significant effect on the movement of combustion gasses in the structure. They also concluded that multivehicle fires cause greater increases in prestressing steel temperatures (and thus greater reductions in steel strength) than do single-vehicle fires, and that large multivehicle fires lead only to minor reductions in prestressing steel strength.