Сalculation of fire resistance of fire protected reinforced concrete structures.

Abstract

A finite-element model was developed for thermal engineering calculation of a fire-resistant multi-cavity reinforced concrete floor in the ANSYS software complex. With the help of the devel oped model, a thermal engineering calculation of a fire-resistant reinforced concrete multi-hollow floor slab was carried out, the essence of which was to solve the problem of non-stationary thermal conductivity and was reduced to determining the temperature of the concrete of the reinforced concrete floor at any point of the cross section at a given time (including at the place of installation of the fittings).A comparison of the results of numerical modeling with the results of an experimental study of fire resistance was carried out. An approach is proposed that allows taking into account all types of heat exchange by specifying cavities as a solid body with an equivalent coefficient of thermal conductivity. The model makes it possible to study stationary and non-stationary heating of both unprotected and fire-protected reinforced concrete structures. At the same time, with the help of the developed model, it is possible to take into account various factors affecting fire-resistant reinforced concrete structures: fire temperature regimes, thermophysical characteristics of reinforced concrete structures, coatings for fire protection of reinforced concrete structures. The adequacy of the developed model was tested, as a result of which it was established that the calculated values of temperatures satisfactorily correlate with experimental data. The largest area of deviation in temperature measurement is observed at the 100 th minute of calculation and is about 3 ºС, which is 9 %. The workability of the developed model for evaluating the fire resistance of fire-resistant reinforced concrete structures and its adequacy to real processes that occur during heating of fire-resistant reinforced concrete structures with the application of a load under the conditions of fire exposure under the standard fire temperature regime have been proven.