Удосконалений метод випробувань залізобетонних колон на вогнестійкість

Abstract

UK: Приведены основные сведения о разработанном методе расчетной интерпретации температурных показателей, полученных в результате испытаний железобетонных колонн на огнестойкость без приложения механической нагрузки. Исследована эффективность метода решения прочностной задачи при определении предела огнестойкости железобетонной колонны по результатам огневых испытаний.

EN: The problem. Testing the concrete columns on fire is carried out in accordance with the applicable standards of Ukraine. According to these standards the column should be subjected to the firing action under the condition of the column load power factors that fully meet the load in the column under the design model of the building. These factors are created by the corresponding nodes of the testing facilities that combine fire oven with the support-loading device. Fire oven has fireproof enclosures, configuration that ensures evenly heating of the construction elements. It is also equipped with fuel- nozzle system on liquid fuel that ensures standard temperature mode of fire. Mechanical load is created by hydraulic press that ensures compressive strength up to 500 t. The implementation of these conditions causes certain technical difficulties such as mismatch of conditions of fixing and loading the column in the construction, mismatch of out-sample for testing and the real column etc. That is why the standard for fire resistance test of columns does not prohibit testing without applying mechanical stress; meanwhile the aforementioned standard does not give any grounded methodology for determining the fire resistance of reinforced concrete columns based on such testing. Moreover, fire test of the columns have limitations on the length of the subjected columns, ways of their fixing, type and size of mechanical loading on the column. Analysis of recent achievements and publications. Analysis of publications on computational methods for designing concrete columns by their fire safety shows that the appointed methods allow to take into account all of the listed features. Therefore the objective of the study is formulated. Statement of the problem and its solution. The purpose of the study is to substantiate the method of solution strength problem to assess the fire resistance of reinforced concrete columns with rectangular cross section calculated on the basis of the interpretation of the results of fire tests. The method of determination of actual fire resistance of reinforced concrete columns is given in the article. The stated method is based on the calculation interpretation of fire tests without applying mechanical stress. To achieve this goal it is necessary to solve the problem of restoration of temperature fields in the cross section of the column by results of point temperature measurement in the inner layers. The methodology of the problem solution is described in the article. Under the terms of the implementation of the developed methods it is necessary to interpolate the results of measurements of temperature in the control points section of reinforced concrete columns. For testing procedures of fire assessment methods by interpreting the results of fire tests appointed testing of two reinforced concrete columns 500 Ч 500 Ч 3 000 from heavy concrete was conducted on granite filler in the fire oven. Conclusions. As a result of the research the following conclusions can be made. 1. Fire testing of reinforced concrete columns was conducted. On the basis of this testing the stability of interpolation methods was investigated. Therefore the most effective method of interpolation was selected. The method is based on approximation of field isotherms. 2. The sequence of procedures of strength calculation method on the basis of temperature measurement in the inner layers of the reinforced concrete column during fire testing was grounded. 27 Вісник ПДАБА 3. The limit of fire resistance of reinforced concrete columns was determined on the basis of interpretation of the data obtained during the fire tests using the proposed method of calculating strength.