• Structural Engineering and Mechanics
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• 제85권5호
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• pp.693-707
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• 2023

In order to deeply reveal the working mechanism of ultra-high performance concrete (UHPC) filled steel tubular columns (UHPCFSTs) under cyclic loading, a three-dimension (3D) macro-mesoscale finite element (FE) model was established considering the randomness of steel fibers and the damage of UHPC. Model correctness and reliability were verified based on the experimental results. Next, the whole failure process of UHPC reinforced with steel fibers, passive confinement effect and internal force distribution laws were comprehensively analyzed and discussed. Finally, a simplified and practical method was proposed for predicting the ultimate bending strengths of UHPCFSTs. It was found that the non-uniform confinement effect of steel tube occurred when the drift ratio exceeded 0.5%, while the confining stress increased then decreased afterwards. There was preferable synergy between the steel tube and UHPC until failure. Compared with experimental results, the ultimate bending strengths of UHPCFSTs were undervalued by the current code provisions such as AISC360-10, EC4 and GB50936 with computed mean values (MVs) of 0.855, 0.880 and 0.836, respectively. The proposed practical method was highly accurate, as evidenced by a mean value of 1.058.

• 한국가구학회지
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• 제27권3호
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• pp.165-174
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• 2016

To modularize the joints of Hanok, the bending strengths of butterfly joints between pre-cut and manual member were compared. Structural size joints were manufactured and the length, width and thickness of each tenon were produced with different sizes. The ultimate load of pre-cut members was 2 times higher than that of manual members. Degree of anchorage for the joints on pre-cut member was also superior to that of manual member. By the F-test results, a great influence between ultimate load and sizes of tenon was found. In result of multiple regression analysis, the length and thickness of tenon were showed proportion relationships with the ultimate load, but the width of tenon was showed inverse proportion with the ultimate load. The results of this study can be used to identify the relationships among the major influence factors. Futhermore, it might be used as basic data for modularization the joints of Hanok.

• International Journal of Concrete Structures and Materials
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• 제8권2호
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• pp.99-116
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• 2014

The American Concrete Institute (ACI) 318-11 permits the use of the moment magnifier method for computing the design ultimate strength of slender reinforced concrete columns that are part of braced frames. This computed strength is influenced by the column effective length factor K, the equivalent uniform bending moment diagram factor $C_m$ and the effective flexural stiffness EI among other factors. For this study, 2,960 simple braced frames subjected to short-term loads were simulated to investigate the effect of using different methods of calculating the effective length factor K when computing the strength of columns in these frames. The theoretically computed column ultimate strengths were compared to the ultimate strengths of the same columns computed from the ACI moment magnifier method using different combinations of equations for K and EI. This study shows that for computing the column ultimate strength, the current practice of using the Jackson-Moreland Alignment Chart is the most accurate method for determining the effective length factor. The study also shows that for computing the column ultimate strength, the accuracy of the moment magnifier method can be further improved by replacing the current ACI equation for EI with a nonlinear equation for EI that includes variables affecting the column stiffness and proposed in an earlier investigation.

• 한국산학기술학회논문지
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• 제17권1호
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• pp.298-303
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• 2016

수직 및 수평의 원형단면 강관으로 구성된 공간프레임 타워는 강재량을 줄이면서도 풍하중의 영향을 완화시킬 수 있는 장점으로 다양한 목적으로 널리 적용되고 있다. 이러한 공간프레임 타워를 하나의 타워구조로 거동하게 하기 위해서는 수직 강관과 수평 강관의 연결부인 강관조인트의 강도 확보가 중요하다. 본 연구에서는 압축과 휨이 동시에 작용하는 강관 T조인트의 강도평가를 수행하였다. AISC, Eurocode3, ISO 19902의 3가지 강관조인트 설계기준을 검토하고, 주강관과 지강관의 세장비를 주요 매개변수로 한 비선형 유한요소해석을 통하여 축력과 모멘트에 대한 극한강도 상호작용을 설계식으로 제안하였다.

• 한국강구조학회 논문집
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• 제16권1호통권68호
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• pp.33-42
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• 2004

SN 강재를 건축구조용으로 사용하기 위해서는 설계기준강도가 제정되어야 한다. 선행 연구로써, SN400B/490B 후판재로 재판한 SN400B/490B 원형강관과 SPAP235/325 및 SPAR295 각형강관의 물성을 평가하였다. SN400B/490B 후판재와 비교했을 때 STKN400B/490B 원형강관의 항복인장 및 인장강도는 상승하였지만, 제조 프로세스에 무관하게 STKN400B/490B 원형강관의 규격을 만족 하였다. 그러나 SPAP235/325 각형강관 모서리부에서의 항복인장 및 인장강도는 규격을 벗어났다. 이것은 SPAP235/325 각형강관 규격에서 정하고 있는 값이 모서리부에서의 값이 아니라 변에서의 값이기 때문이다. STKN490B 원형강관에 발생한 최대 인장잔류응력은 모재 항복강도 수준이며, 최대 압축잔류응력은 모재 항복강도의 40% 수준이었다. 또한 SPAP325 각형강관에 발생한 최대 인장잔류응력과 최대 압축잔류응력은 모두 모재 항복강도의 80% 수준이었다. 중심압축실험을 한 결과 STKN490B 원형강관의 좌굴강도는 제조 프로세스에 관계없이 별 차이를 보이지 않았다. 그러나 각형강관의 경우는 SPAP325 각형강관이 SN490B로 built-up한 각형강관보다 좌굴강도가 높게 나타났다.

• Steel and Composite Structures
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• 제38권5호
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• pp.599-615
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• 2021

The ultimate strength behaviour of sandwich composite beams with J-hooks and normal weight concrete (SCSSBJNs) are studied through two-point loading tests on ten full-scale SCSSBJNs. The test results show that the SCSSBJN with different parameters under two-point loads exhibits three types of failure modes, i.e., flexure, shear, and combined shear and flexure mode. SCSSBJN failed in different failure modes exhibits different load-deflection behaviours, and the main difference of these three types of behaviours exist in their last working stages. The influences of thickness of steel faceplate, shear span ratio, concrete core strength, and spacing of J-hooks on structural behaviours of SCSSBJN are discussed and analysed. These test results show that the failure mode of SCSSBJN was sensitive to the thickness of steel faceplate, shear span ratio, and concrete core strength. Theoretical models are developed to estimate the cracking, yielding, and ultimate bending resistance of SCSSBJN as well as its transverse cross-sectional shear resistance. The validations of predictions by these theoretical models proved that they are capable of estimating strengths of novel SCSSBJNs.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1993년도 가을 학술발표회 논문집
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• pp.284-289
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• 1993

To analyze the effects of compressive strength of concrete and longitudinal steel ratio on buckling behavior of columns, 36tied reinforced concrete columns with hinged ends were tested. The 100mm square cross section was used and the amount of eccentricity was 10mm. The compressive strengths of column specimens with slenderness ratios of 15, 30 and 50 were 202, 513 and 752 kg/$\textrm{cm}^2$. The longitudinal steel ratio of columns with bending about a section diagonal and about a principal axis were 2.85%(4-D10). The ratio of ultimate load capacity to that of short column with the same eccentricity was much decreased at high slenderness ratio with increasing the compressive strength of concrete. And the lateral displacement of column at the ultimate load was decreased as the strength was increased. These are due to that at high slenderness ratio, the load capacity and behavior of column are affected by flexural rigidity. And, it was also found that for the same quantity of confining steel and level of axis load, there is little difference between the flexural strength for bending about a section diagonal and for bending about principal axis.

• Steel and Composite Structures
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• 제25권4호
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• pp.457-472
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• 2017

The objective of this paper is to investigate the flexural behavior of concrete-filled round-ended steel tubes (CFRTs) under bending. Beam specimens were tested to investigate the mechanical behavior of the CFRTs, including four CFTs with different concrete strengths and steel ratios, and three CFRTs with varied aspect ratios. The load vs. deflection relationships and the failure modes for CFRTs were analyzed in detail. The composite action between the core concrete and steel tube was also discussed and examined based on the experimental results. In addition, ABAQUS program was used to develop the full-scale finite element model and analyze the effect of different parameters on the moment vs. curvature curves of the CFRTs bending about the major and minor axis, respectively. Furthermore, design formulas were proposed to estimate the ultimate moment and the flexural stiffness of the CFRTs, and the simplified theoretical model of the moment vs. curvature curves was also developed. The predicted results showed satisfactory agreement with the experimental and FE results. Finally, the differences of the experimental, FE and predicted results using the existing codes were illustrated.

• Steel and Composite Structures
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• 제38권3호
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• pp.319-336
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• 2021

To achieve a rational detail of the girder-abutment joints in composite integral bridges, and validate the performance of the joints with perfobond connectors, this paper proposes two innovative types of I-shaped steel girder-concrete abutment joints with perfobond connectors intended for the most of bearing capacity and the convenience of concrete pouring. The major difference between the two joints is the presence of the top flange inside the abutments. Two scaled models were investigated with tests and finite element method, and the damage mechanism was revealed. Results show that the joints meet design requirements no matter the top flange exists or not. Compared to the joint without top flange, the initial stiffness of the one with top flange is higher by 7%, and the strength is higher by 50%. The moment decreases linearly in both types of the joints. At design loads, perfobond connectors take about 70% and 50% of the external moment with and without top flange respectively, while at ultimate loads, perfobond connectors take 53% and 26% of the external moment respectively. The ultimate strengths of the reduced sections are suggested to be taken as the bending strengths of the joints.

• Advances in concrete construction
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• 제1권3호
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• pp.215-225
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• 2013

The results of experimental testing of the effect of confined concrete on compressive strength and ductility of concrete beam subjected to pure bending are presented. The effect of different stirrups forms and spacing, as well as different concrete strengths, on beam carrying capacity and ductility were analyzed. Ultimate strength capacity and deflection of concrete beam increase with the decrease in stirrups spacing. Stirrup form has a great effect on the ultimate carrying capacity and ductility of concrete beam. Stirrups which confined the region of concrete in the compression more contribute to greater compression strength of concrete than common stirrups at the perimeter of the entire cross-section of the beam.