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• 콘크리트 충전 팔각 강관합성기둥의 압축강도평가(Evaluation of Compression Strengths of Octagonal Concrete-Filled Tube Columns)

• 저자: 임종진, 엄태성

• Abstract: In this study, the axial compression behavior of concrete-filled octagonal tube columns (OCFT columns) was experimentally investigated. Eight OCFT column specimens designed as the slender and noncompact sections using thin-walled tubes were prepared for the compression test. The wall thickness, fabrication detail, and section shape of the thin-walled tubes were considered as the test parameters. The test results showed that the buckling mode of the tubes and the compressive strength of the columns were affected by the test parameters. By using the thick tube wall and section geometry close to a circle, the local buckling of the tube wall was delayed and thus the column strengths were increased. The theoretical strengths of the OCFT columns computed in accordance with the provisions for filled composite columns specified in KBC 2016 and AISC 360-16 were compared with the test strengths.

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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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• 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.