DETERMINATION OF THE ZONE OF THERMAL INFLUENCE OF FIRE BY RESULTS INSPECTION OF FLOOR STRUCTURES

Abstract

The results of the study of the technical condition of 14 round-hollow slabs according to the series II-03-02 within the basement of two entrances of a residential building after a fire, lasting about 8 hours. More than 40 years passed from the commissioning of the building to the fire, and all this time the basement slabs were in a non-aggressive environment, but with high relative humidity, which had a positive effect on increasing the concrete strength of typical slabs. Inspection of slabs in adjacent rooms for a long time of operation did not reveal significant defects from their humidification and insufficient thermal insulation properties of the floor above the basement.
 In the inspection area, some floor slabs above the basement were found to be defective due to high temperatures, which reduced their rigidity.
 The information obtained from the survey is necessary to perform verification calculations to determine the load-bearing capacity and stiffness of the floor slabs and compare them with the data from the survey results. The data of test calculations are also needed to substantiate the need for reinforcement work on the slabs, to ensure their further normal operation on the operating loads on the ground floor.
 To analyze the impact on the deflections of slabs of constant and payloads, some of their actions are considered and verified calculations of the deflections of the floor slabs for the four adopted separate stable modes of normal operation.
 A histogram of the change in the actual deflections of the floor slabs above the basement is constructed, according to the analysis of which the area with the largest deflections is clearly traced, which indicates the location of the highest temperatures in this place. That is, the level of vertical deformations of floor slabs can determine the relative temperature distribution within them. Deflections of slabs due to high temperatures should be considered as damage that interferes with normal operation and significantly reduces the durability of slabs.
 Considered after the fire condition of the slabs showed that in the absence of impact on them payloads, the obtained additional temperature deflections are greater than the calculated, which are obtained by verification calculations for the action of full operating loads.
 Also offered different options for strengthening both the slabs themselves and the seams between them, for their joint work on different combinations of loads.