Безопасность техногенных и природных систем (Dec 2018)
ON THE ULTRASONIC METHOD OF INVESTIGATION OF REINFORCED CONCRETE STRUCTURES AFTER A FIRE
Abstract
The article is devoted to the ultrasonic method of investigation of reinforced concrete structures after a fire. The method is based on the property of an ultrasonic wave to change the speed of passage, depending on the degree of damage to thereinforced concrete structure as a result of a fire. The method is widely used in the practice of fire and technical expertise to establish a fire in the room. The aim of the work is to derive a formula relating the transmission coefficient of an ultrasonic wave to the temperature of the concrete heating. The resulting formula should transmit the temperature of the fire impact to the reinforced concrete structure in the event of a fire as accurately as possible. In the Microsoft Excel software system, graphswere constructed to study the linear and polynomial dependence of the ultrasonic wave transmission coefficient and the temperature of concrete heating. The equations obtained as a result of the study were tabulated and compared for the purpose of determining the equation with a minimum measurement error.As a result of the study, an equation was obtained that establishes the relationship between the transmission coefficient of the ultrasonic wave and the temperature of the concrete heating. Verification of the equation obtained showed that themaximum error in the results is 20 ° C at a concrete heating temperature of 400 ° C, which is very insignificant. On the basis of the obtained equation, an algorithm was constructed for calculating the temperature of heating concrete and itsmain strength characteristics at a known rate of passage of an ultrasonic wave. Creating a program based on the algorithm described in this article will improve the ultrasonic flaw detector and expand its functions. The improved ultrasonic flaw detector will be useful both to the staff of forensic institutions of the federal firefighting service "Test Fire Laboratory", indetermining the fire site, and to organizations carrying out an assessment of the residual loadbearing capacity of reinforced concrete structures after a fire.
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