Análise do comportamento estrutural de vigas de concreto armado submetidas às altas temperaturas utilizando a metodologia do planejamento fatorial.

Abstract

Fire situations in reinforced concrete structures’ building are common because the widespread use of structural material. However, the analysis and measurement of the damage caused by these claims still need more details and the relationship between the variables that influence the structural capacity should be examined together. Therefore, this work presents the analysis of the structural behavior of reinforced concrete beams subjected to high temperatures with parameters of coatings and water-cement ratio analyzed together with the temperature levels through the statistical experimental design 2³ in central composite rotational design (CCRD). The factorial design was used from the selection of variables, the definition of the levels and the post-processing data. Thus defined the materials and their proportions, were made 48 beams reduced with different coatings and water-cement factors. After the curing process and drying, the beams were subjected to different levels of temperature and analyzed the variation in the capacity of the beams subjected to simple bending through its curve of load x deflection. An analogous procedure was performed for 29 specimens were tested to simple compression. With samples of the specimens and the beams also were conducted thermogravimetry tests, scanning electron microscopy and diffraction of x-rays intended to detect the effect on the cement hydration products and relate them with the loss of resistant capacity. At the end, comparing statistical and microstructural results, it was found the predominant influence of the variable factors water / cement and that there is intersection between w/a ratio and temperature at which concrete gains strength and has its accelerated hydration process in the formation of portlandite and tobermorite detected. The findings open the way for discussion of the protection of structures under fire situation by controlling water-cement ratio.Fire situations in reinforced concrete structures’ building are common because the widespread use of structural material. However, the analysis and measurement of the damage caused by these claims still need more details and the relationship between the variables that influence the structural capacity should be examined together. Therefore, this work presents the analysis of the structural behavior of reinforced concrete beams subjected to high temperatures with parameters of coatings and water-cement ratio analyzed together with the temperature levels through the statistical experimental design 2³ in central composite rotational design (CCRD). The factorial design was used from the selection of variables, the definition of the levels and the post-processing data. Thus defined the materials and their proportions, were made 48 beams reduced with different coatings and water-cement factors. After the curing process and drying, the beams were subjected to different levels of temperature and analyzed the variation in the capacity of the beams subjected to simple bending through its curve of load x deflection. An analogous procedure was performed for 29 specimens were tested to simple compression. With samples of the specimens and the beams also were conducted thermogravimetry tests, scanning electron microscopy and diffraction of x-rays intended to detect the effect on the cement hydration products and relate them with the loss of resistant capacity. At the end, comparing statistical and microstructural results, it was found the predominant influence of the variable factors water / cement and that there is intersection between w/a ratio and temperature at which concrete gains strength and has its accelerated hydration process in the formation of portlandite and tobermorite detected. The findings open the way for discussion of the protection of structures under fire situation by controlling water-cement ratio.