USE OF RESIDUAL LIFE OF REINFORCED CONCRETE FLOOR AFTER FIRE
Array
Keywords:
residual γ% - resource, reinforced concrete, fire, bearing capacity, impact of fire, strength of structures.Abstract
The article discusses the rational use of steel-reinforced concrete structures that have experienced exposure to high temperatures after a fire. The existing practice of restoring metal structures after a fire is based, as a rule, either on their replacement, or on comprehensive reinforcement. In this case, a detailed analysis of the technical condition of individual parts of the building as a whole, but only of individual elements with an assessment of the degree of damage and the possibility of further use, is not performed. The study allows you to evaluate structures from the point of view of the prospects for their use not by separate elements, but by the entire volume of a specific entire section of the building (floor, walls, frame, etc.). The reinforced concrete monolithic attic floor of the administrative building of 1938, which was exposed to high temperatures from a fire, is considered as the initial construct. The temperature of the fire reached 700 ° C. The total area of fire exposure was 1680 m2. As a result, some of the load-bearing metal I-beams received significant deflections reaching 14 cm at a span of 96 m, and some of the beams bent only within 1-3 cm. An analysis of the strength parameters of the beams after the fire showed that their yield strength decreased only by 5-7 % To assess the possibility of further reliable use of the entire floor (the reinforced concrete floor between the metal beams was not damaged), we calculated γ% - a resource according to the theory of reliability with the task of the variational series of defects of the bearing beams and their possible service life. Based on the calculation, it was possible to establish that with a 75% gamma resource, the floor can be reliably operated for 25 years, while replacing a damaged floor is impractical. It was recommended to replace only 4 of the 54 beams, which significantly reduced the total cost of restoring the floor. Using the gamma resource parameter significantly increases the determination of the reliability and durability of the considered parts of the building when analyzing various adverse effects on these parts.
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