IMPROVEMENT OF THE ZONE METHOD OF CHECKING THE FIRE RESISTANCE OF A HOLLOW-CORE SLAB

Abstract

The work analyzes the existing methods used to determine the fire resistance of hollow-core reinforced concrete slabs. There were carried out numerical experiments using thermal mathematical models of hollow-core reinforced concrete slabs under conditions of fire with duration of 30 minutes, 45 minutes, 60 minutes, and 90 minutes. The functioning of these models is based on the non-stationary differential equation of thermal conductivity with numerical approximation using the finite element method. Based on the results of the numerical experiments, the load-bearing capacity of the sectional reinforced concrete slab was determined with duration of fire exposure of 30 minutes, 45 minutes, 60 minutes, and 90 minutes, according to the proposed simplified zone method and the zone method recommended by the standards. Thus, during the research there was developed a simplified method for checking the fire resistance of hollow-core reinforced concrete slabs. The proposed method is based on determining the damaged layer of concrete in the centers of the half-section zones of hollow-core reinforced concrete slabs, as well as taking into account the thermal influence of a fire on the strength characteristics of steel reinforcement bars. According to the results of a comparative analysis of the existing and proposed method, it was established that the error does not exceed 6% with a fire exposure lasting 90 minutes, which demonstrates high efficiency in using the proposed method and the possibility of its application for calculating the fire resistance of hollow-core reinforced concrete slabs.