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고강도강재를 적용한 비대칭 하이브리드 합성보의 휨거동 실험
전수찬,한규홍,이철호,김진원,Jun, Su Chan,Han, Kyu Hong,Lee, Cheol Ho,Kim, Jin Won 한국강구조학회 2017 韓國鋼構造學會 論文集 Vol.29 No.3
본 연구에서는 고강도강재를 적용한 비대칭 하이브리드 합성보의 휨성능을 실물대 실험을 통하여 평가하였다. 합성보의 웨브와 상부플랜지에는 일반강재(SM400, SM490)를 적용하고 하부플랜지는 상부플랜지에 비해 상대적으로 크게 제작하여 비대칭 단면으로 적용한 후 일반강재(SM520) 및 고강도강재(SM570, HSA800)를 각각 적용하였다. 본 연구의 주요 목적은 비대칭 하이브리드 합성보의 휨성능 평가 및 설계지침의 개발이다. 실험결과 하부플랜지에 일반강재를 적용한 실험체의 경우 $Dp/Dt{\leq}0.15$를 만족시킬 시 우수한 휨강도와 연성능력을 발현하는 것을 확인하였다. 반면 하부플랜지에 고강도강재가 적용된 실험체의 경우 휨내력의 증가로 인한 슬래브의 수평전단력 증가가 예상치 못한 슬래브 종방향 전단파괴를 발생시켜 소성강도에 도달하지 못하였다. 따라서 고강도강재를 적용한 비대칭 하이브리드 합성보의 경우 설계단계에서 슬래브 수평전단강도 확보가 필수적이다. Full-scale flexural testing of asymmetric H-shape hybrid composite beams was conducted in this study. In fabricating hybrid H-shape sections, high strength steels were utilized for the bottom flange while ordinary strength steels were used for the top flange and web. With adding a fully composite floor slab, a total of 8 hybrid composite beam specimens were tested. The primary objective was to develop the asymmetric hybrid H-shape composite beams with maximized flexural efficiency and investigate their flexural behavior. Not all the hybrid composite specimens tested in this study exhibited the plastic moment and reasonable deformability. In the specimens with high-strength bottom flange, the longitudinal shear crack of the slab along the beam axis often preceded the development of beam plastic moment, although the slab was designed as fully composite. The mechanical reason for this unexpected behavior is discussed. It is emphasized that the longitudinal shear strength of composite slab should be checked in designing hybrid composite beams utilizing high strength steels like in this study.
Experimental Evaluation of Negative Flexural Capacity of Composite Slabs Embedded with Truss Girders
전수찬,이철호,Bae Chang-Jun,Chung Gi-Taek 한국강구조학회 2024 International Journal of Steel Structures Vol.24 No.3
In this study, a novel composite slab integrating truss girders was introduced. Flexural tests were conducted on a total of eight composite slab specimens to evaluate their negative fl exural capacities. Based on the test results, the negative fl exural behavior of the composite slabs was analyzed, including the development of catenary action, and the eff ects of truss girders and diagonally bent integrity reinforcements. All specimens showed satisfactory performance in terms of their fl exural strength and stiff ness and exhibited high ductility capacities. The test specimens did not show any noticeable degradation in fl exural strength, and the tests were terminated due to the displacement stroke limitation of the actuator. Strain measurements clearly indicated an eff ective transition of the negative moment-resisting mechanism from fl exural to catenary action at large deformations, causing the entire section to be subjected to tensile forces. The development of catenary action was the main reason for the high ductility observed in the specimens. The truss girders, although not spanning the entire width of the supporting beams, eff ectively enhanced the negative fl exural strength of the composite slabs as their ends partially extended through the critical failure section. The eff ects of the truss girder were particularly notable in specimens supported by H-section beams, where the negative fl exural strengths increased by about 10 –20%. Furthermore, diagonally bent integrity reinforcements, primarily introduced for ease of construction, were also found to eff ectively increase the negative fl exural strength of the composite slabs by developing tensile forces when diagonal cracks developed in concrete sections.
전수찬(Jun, Su-Chan),이철호(Lee, Cheol-Ho),배창준(Bae, Chang-Jun),김성용(Kim, Sung-Yong) 대한건축학회 2020 大韓建築學會論文集 : 構造系 Vol.36 No.3
In this paper, the ASCE 7 equivalent static approach for seismic design of non-structural elements is critically evaluated based on the measured floor acceleration data, theory of structural dynamics, and linear/nonlinear dynamic analysis of three-dimensional building models. The analysis of this study on the up-to-date database of the instrumented buildings in California clearly reveals that the measured database does not well corroborate the magnitude and the profile of the floor acceleration as proposed by ASCE 7. The basic flaws in the equivalent static approach are illustrated using elementary structural dynamics. Based on the linear and nonlinear dynamic analyses of three-dimensional case study buildings, it is shown that the magnitude and distribution of the PFA (peak floor acceleration) can significantly be affected by the supporting structural characteristics such as fundamental period, higher modes, structural nonlinearity, and torsional irregularity. In general, the equivalent static approach yields more conservative acceleration demand as building period becomes longer, and the PFA distribution in long-period buildings tend to become constant along the building height due to the higher mode effect. Structural nonlinearity was generally shown to reduce floor acceleration because of its period-lengthening effect. Torsional floor amplification as high as 250% was observed in the building model of significant torsional irregularity, indicating the need for inclusion of the torsional amplification to the equivalent static approach when building torsion is severe. All these results lead to the conclusion that, if permitted, dynamic methods which can account for supporting structural characteristics, should be preferred for rational seismic design of non-structural elements.