Papers by Keyword: Mechanical Properties at High Temperature

Abstract: A fire occurred in the steel framed building could be yielded an unexpected disasters including loss of human lives and damages of properties. Therefore, to evade the tragedies from the building, fire resistance performance of structural elements is required and specified into each nation’s building regulation. Especially, the structural beam plays a key role to transfer the load applied on the floor to column. In this study, to estimate the fire resistance performance of structural beam made of SM 400, analysis using not only mechanical, thermal properties at high temperature of the SM 400 but theories of heat transfer and thermal stress were conducted. The result of this study showed that as the lengths of beam are increased, the structural stability become getting worse. Therefore, it is not recommended to use the same thickness of fire protective materials derived from prototype’s length, 4100 mm to longer beam.

Abstract: Fire resistance of structural elements such as columns and beams has been evaluated by the fire test. However, needs of fire design based on analysis using a heat transfer theory and a stress analysis are increasing because the design can reduce not only the period of the fire test but the cost of it. The reliability of the analysis would be totally dependent on the mechanical, thermal databases of their structural steels. This paper evaluates the fire resistance of ordinary grade structural steels manufactured from Korea by examining the mechanical and thermal properties of SS 400, SM 400, and SM 490 at high temperature and comparing them with those defined in Eurocode 3. The results showed that the ordinary structural steel had almost the same characteristics as those in Eurocode 3.

Abstract: Material strength is one of the most important factors in designing a building. For this reason, many structural steel manufacturers have been trying to develop it. In Korea, SM 570 is one high structural steel that has many merits such as longer span and reduction of construction cost for steel works. However, the fire resistance performance of H-section made of SM 570 has not been evaluated. Especially, in high-rise steel building that can be built with various joint systems like hinged to hinge, hinge to fixed, and fixed to fixed. However, the performance of fire resistant is limited. In this paper, to evaluate the fire resistance of H-section made of SM 570, the advanced fire design was conducted using regressive equation of the mechanical and thermal properties at high temperature, compared with those made of an ordinary structural steel, SS 400. The facts show that hinge to hinge had the lowest load bearing capacity at high temperature. Therefore, to keep the same fire resistance with other types boundary conditions, the more passive fire materials are required.

Abstract: As the strength of structural steels is increasing, the performance of fire resistance should be evaluated clearly and suggested. While their application has been expanded, the evaluation of the fire resistance is inclined to adopt that derived from ordinary strength steels. In order to compare the fire resistance performance of high strength structural steels at high temperature, databases such as mechanical and thermal properties at elevated temperature were compared with those of Eurocode 3. After comparison, it is recommended that the passive protective material is more needed than those for the ordinary strength structural steels to meet the fire resistance requirement.

Abstract: Building construction has been developed with an increase of steel application at main members, but the weakness should be resolved with a proper fire resistance. The fire engineering method is regarded as an alternative way to evaluate the fire resistance with mechanical and thermal properties at high temperature. In this paper, the fire resistance of H-section built with ordinary grade structural steels such as SS 400 and SM 490 those are representative structural steels at the construction market were analyzed by the difference of boundary conditions. The study showed that the H-section made of SM 490 represented little difference in reduction ratio of an allowable stress at one hour standard fire curve. And the hinge to hinge boundary condition from both H-sections was the lowest. As the grade of structural steel rises, the difference in an allowable stress at high temperature according to grade of structural steels is inclined to increase.

Abstract: Fire resistance of H-section by types of boundary condition such as hinge to hinge, hinge to fixed, and fixed to fixed at high temperature can be different. However, the study of evaluation is very limited. In this study, to estimate the fire resistance of H-section made of ordinary structural steel, SS 400, a fire engineering method was used with applying materials properties at high temperature and a heat analysis, a stress analysis. The results showed that hinge to hinge boundary condition was the lowest at an allowable stress at high temperature. Therefore, the application of the hinge to hinge is more conservative boundary condition in H-section connection in high temperature.

Abstract: The effects of coatings on the creep and oxidation behavior of Ti-50Al alloy were investigated at 1173K in air at a constant loading of 30MPa. The coating was formed by a two-step Cr/Al diffusion treatment and consisted of an outermost TiAl2 layer, an outer Al-rich γ layer, an intermediate γ, Laves and β mixture layer, and a Cr diffusion zone. Creep tests were also carried out with sole Cr or Al coated TiAl and also of uncoated TiAl. The oxide scales formed on the uncoated TiAl and the sole Cr coated specimens were a mixture of TiO2 and Al2O3, which displayed several exfoliations. Both the two-step Cr/Al coated TiAl and the sole Al coated specimens formed a protective Al2O3 layer and little oxide exfoliation was observed here. Significant cracks were observed in the sole Al coated TiAl, while no cracks were observed in the sole Cr coated TiAl; the two-step Cr/Al coated TiAl showed a number of cracks in the coatings. Low creep rates in the two-step Cr/Al coated TiAl could be due to the Laves phase with a hexagonal C14 structure in the intermediate, γ, β and Laves phase mixture, and the high creep rates of the sole Cr coated TiAl may originate in the major β phase component with a B2 structure in the γ, β, and Laves phase mixture.