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• 매입형 합성기둥에 사용된 앵글 단부강판접합부의 거동 및 성능평가 (Behavior and Performance Evaluation of Bolted End-Plate Splice of Angles Used in Encased Composite Columns)

– 저자 : 엄태성, 양종민, 김대경, 이승환

In this study, a bolted end plate splice method of steel angles for concrete-encased composite columns is proposed. For the splice, thick end plates are welded at the end of spliced angles, and are snug-tightened face-to-face with one or three high-strength bolts. Since the geometrical centers of angle and bolt sections do not coincide, the prying force caused by deformation of the end plate needs to be addressed in the splice design. Thus, a minimum thickness of the end plate is proposed based on the yield line theory, and the connection strength addressing the prying force is suggested. The performance of the bolted end plate splice of angles are investigated through direct tension tests of angle splices and flexural tests of encased composite columns with angle splices. The tests show that the bolted end plate splice of angle is susceptible to slip and rupture in the threaded portion of the bolts, due to the deformation of the connection and the prying action. The proposed minimum end plate thickness and connection strengths correlate reasonably with the test results.

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• 앵글과 철근을 조립한 PSRC 합성기둥의 휨실험

– 저자 : 황현종, 엄태성, 박홍근, 이창남, 김형섭

건물의 대형화 및 초고층화로 인하여 효율적인 구조방식으로 강-철근콘크리트 합성구조(SRC 구조)의 적용이 확대되고 있다 SRC 기풍의 휩강도 효율을 높이고 강재가 콘크리트 행보강에 기여하도록 하기 위해서는 강재를 최대한 단면 코너에 배치하는 것이 효과적이다，김형근 등은 단연성능을 향상시키고 거푸집 공사와 배근공사를 생략할 수 있도록， 앵글을 단연의 4개 코너에 배치하고 y형 강판으로 앵글 사이를 용접하여 기풍을 구속하는 yLRC 합성기풍을 제안하였다 압축실험 결과 앵글과 y형 강판에 의한 콘크리트 구속효과로 최대하중 변형률이 증가하였으나 최대강도 이후 앵글의 좌굴에 의한 급격한 강도감소를 보였으며， 김보랍등에 의하면 강재가 외부에 노출되어 내화띠복이 추가되어야하는한계가있었다. Campione와 Montuori 등은 철근콘크리트 기퉁을 앵글로 보강하여 중심축 및 편심 압축 가력을 수행하였다 기존 철근콘크리트 기둥을 보강하기 위하여 기퉁 외부 네 코너에 앵글을 설치한 후 강판을 용접하여 앵글을 일체화 시켰다 그 결과 기퉁 코너에 배치된 앵글에 의한 추가적인 구속 효과로 인하여 기풍의 강도 및 연성능력이 증가하는 것으로 나타났다 그러나 앵글이 기퉁 외부에 설치되므로 내화피복이 추가로 필요하고， 앵글 좌굴을 방지하기 위해 앵글에 띠강판을 츰총하게 용접을 해야 한다 이러한 한계를 극복하고 앵글을 주요 구조부재로 사용하기 위하여， 본 연구에서는 앵글을 콘크리트 기둥 내부에 배치하는 새로운 합성기풍을개발하였다

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• 고강도 앵글을 적용한 선조립 합성기둥의 압축 실험

– 저자 : 황현종, 엄태성, 박홍근, 이창남, 김형섭

본 연구에서는 고강도 앵글을 사용한 선조립 합성기둥(PSRC 합성기둥)을 연구하였다. 2/3 축소모델의 PSRC 실험체 및 단면 중앙부에 H형강을 매입한 일반 SRC 실험체를 제작하여 중심압축실험을 수행하였다. 강재비와 횡철근 간격을 실험 변수로 고려하였다. 실험결과 단면 코너부 앵글에 의한 콘크리트 구속효과로 인하여 PSRC 합성기둥 실험체는 일반 SRC 합성기둥과 비교하여 하중 재하능력 및 변형능력이 우수한 것으로 나타났다. 또한 KBC 2009 설계기준에 의한 공칭압축강도보다 높은 하중저항능력을 나타냈다. 기존의 횡보강 콘크리트 재료모델을 적용하여 단면해석을 수행한 결과, 초기강성, 최대강도, 최대강도 이후의 강도 및 강성 저하 등에서 실험 및 해석결과가 비교적 잘 일치하는 것으로 나타났다.

In this study, prefabricated composite columns using high-strength angles (PSRC composite column) was studied. Concentric axial loading tests were performed for 2/3 scale PSRC specimens and an conventional SRC specimen with H-steel at the center of the cross-section. The test parameters were the steel ratio of angles and the spacing of lateral re-bars. The test results showed that by placing the angles at the corners of the cross-section for confinement with provided for the core concrete, the PSRC column specimens exhibited greater load-carrying capacity and deformation capacity than those of the conventional SRC column. The axial load-carrying capacity of the PSRC columns was greater
than the prediction by KBC 2009. Using existing stress-strain relationship of confined concrete, the axial load-deformation relationship of the specimens were predicted. The numerical predictions correlated well with the test results in terms of initial stiffness, load-carrying capacity, and post-peak strength- and stiffness- degradations

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• 앵글과 철근을 조립한 PSRC 합성기둥의 휨 실험

– 저자 : 엄태성, 황현종, 박홍근, 이창남, 김형섭

PSRC column is a concrete encased steel angle column. In the PSRC column, the steel angles placed at the corner of the cross-section resists bending moment and compression load. The lateral re-bars welded to steel angles resist the column shear and the bond between the steel angle and concrete. In the present study, current design procedures in KBC 2009 were applied to the flexure-compression, shear, and bond design of the PSRC composite column. To verify the validity of the design method and failure mode, simply supported 2/3 scaled PSRC and correlated SRC beams were tested under two point loading. The test parameters were the steel angle ratio and lateral bar spacing. The test results showed that the bending, shear, and bond strengths predicted by KBC 2009 correlated well with the test results. The flexural strength of the PSRC specimens was much greater than that of the SRC specimen with the same steel ratio because the steel angles were placed at the corner of the column section. However, when the bond resistance between the steel angle and concrete was not sufficient, brittle failures such as bond failure of the angle, spalling of cover concrete, and the tensile fracture of lateral re-bar occurred before the development of the yield strength of PSRC composite section. Further, if the weldability and toughness of the steel angle were insufficient, the specimen was failed
by the fracture of the steel angle at the weld joint between the angle and lateral bars.

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• TSC 합성보 – PSRC 합성기둥 접합부에 대한 주기하중 실험 (Cyclic Loading Test for TSC Beam – PSRC Column Connections)

– 저자 : 황현종, 엄태성, 박홍근, 이창남, 김형섭

In the present study, details of the TSC beam-to-PSRC column connection for low and middle seismic zones were developed. For ease construction, the top and bottom flanges of the steel section of the TSC beam were discontinuous at the joint face on purpose, while the web passes through the joint. Thus, tensile resistance of the top and bottom flanges is not considered in the calculation of nominal strength of the connection. Cyclic loading tests on two interior connections and an exterior connection were performed to verify the seismic performance. The test parameter for two interior connections was the depth of the TSC beams: 600 and 700 mm including the slab depth. The test results showed that the nominal strength of the connections predicted by KBC 2009 correlated well with the test results. The connection specimens exhibited relatively good deformation and energy dissipation capacities, greater than the requirements for the ordinary and intermediate moment frames. Ultimately, the connection specimens were failed at the story drift ratios of 3.0 to 4.0 % due to local buckling and tensile fracture of the web of the TSC beam passing through the joint. By modifying the existing provisions of ASCE, the joint shear strength of the TSC beam-PSRC column connection was evaluated.

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• PSRC 합성기둥의 반복가력 실험 (Cyclic Loading Tests for Prefabricated Composite Columns Using Steel Angle and Reinforcing Bar)

– 저자 : 황현종, 엄태성, 박홍근, 이창남, 김형섭

PSRC composite column is a concrete encased steel angle column. In the PSRC composite column, the steel angles placed at the corner of the cross-section resists bending moment and compression load. In the present study, using the performance criteria in KBC 2009, cyclic lateral loading test was performed for PSRC columns to verify the seismic performance. The test parameters were the column type, the use of continuous hoop, and the use of studs for steel angle. 2/3 scale specimens of a conventional composite column and three PSRC columns were tested. The test results showed that the load-carrying capacity predicted by KBC 2009 correlated well with the test results. The specimens also exhibited good deformation and energy dissipation capacities. After concrete cover spalling under cyclic loading, the load-carrying capacity were decreased by buckling of longitudinal bars and steel angles. When continuous hoop was used, the deformability of the PSRC column was improved, preventing early buckling of the steel angles.