Numerical approach for structural analysis of steel-concrete composite columns exposed to elevated temperature = 고온에 노출된 강재-콘크리트 합성기둥의 거동에 대한 수치해석

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This paper introduces a numerical analysis method to evaluate the residual fire-resistance of steel-concrete composite structures. The proposed analysis method consists of two procedures, a transient heat transfer analysis and a non-linear structural analysis. To precisely simulate the structural response with temperature, the material properties of concrete and steel according to the two representative temperature conditions, “under-fire” and “after-cooling”, have been taken into account. Furthermore, non-mechanical strains of concrete and steel such as thermal strain, transient strain, and creep strain, which change with temperature variation induced by fire, are implemented into the formulation. Upon validation of the introduced numerical method through a correlation study between experimental data and numerical results, the importance of the exact consideration of the non-mechanical strains as well as material properties of concrete and steel corresponding to the changing temperature has been emphasized. Moreover, through a comparison of the numerical results with the design code EN1992-1-2, it has been concluded that the design code should consider the influence of temperature decrease after experiencing high temperature to ensure the safety of fire-damaged structural members. In addition to fire-resistance evaluation, a numerical model for the analysis of bond-slip occurring in concrete filled steel tube (CFT) columns is introduced. Unlike the classical bond-link or bond-zone element using double nodes, the introduced model considers the bond-slip effect without taking double nodes by incorporation of the equivalent steel stiffness. Moreover, while solving the system equation to evaluate the slip behavior, the mechanical properties for steel and bond-slip have been changed and updated through an iteration procedure and the validity of the introduced numerical model is verified by comparing the experimental data with the analytical results for CFT columns subjected to axial force and bending moment. Finally, a simple design equation to predict the resisting capacity of circular CFT columns is introduced, and the accompanying design procedure entails two phases: construction of the linearized P-M interaction diagram for a circular CFT column section and its adjustment according to the slenderness ratio. To construct the linearized P-M interaction diagram of circular CFT columns without a rigorous nonlinear analysis, simple equations are proposed in this paper. The ultimate resisting capacities calculated by the proposed design equation are compared with those constructed from rigorous nonlinear analyses and from the AISC design guideline and the Eurocode with the objective of establishing the relative efficiencies of the proposed equation. Finally, the numerical model of a CFT column subjected to high temperature is suggested considering with the concept of gap conductance and modified bond-slip relation. Comparisons with experimental results verified that the suggested model well describes the change of composite behavior at the interface between steel and concrete under the elevated temperature.
Kwak, Hyo-Gyoungresearcher곽효경researcher
한국과학기술원 :건설및환경공학과,
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학위논문(박사) - 한국과학기술원 : 건설및환경공학과, 2018.2,[vi, 109 p. :]


steel-concrete composite column▼afire resistant capacity of concrete▼aafter-cooling analysis▼aresidual resistance▼adesign code▼abond-slip▼aCFT column▼abond stress▼aultimate load▼aP-M interaction diagram; 강재-콘크리트 합성 기둥▼a콘크리트 내화성능▼aafter-cooling analysis▼a잔류저항력▼a구조설계기준▼a부착-슬립 효과▼aCFT 기둥▼a부착응력▼aP-M 상관도

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