• 콘크리트학회논문집
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• 제23권6호
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• pp.781-790
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• 2011

이 연구는 다양한 보강상세를 갖는 CFRP(carbon fiber reinforced polymer)로 표면매립 보강된 철근콘크리트보의 보강효과에 관한 실험연구이다. 다양한 보강상세를 갖는 표면매립공법의 보강효과를 분석하기 위해 실험변수로 CFRP 보강재의 단면형상, 보강량, 매립 개수 및 위치 등의 다양한 보강상세를 적용하여 총 14개의 실험체를 제작하였다. 실험 결과, 표면매립보강의 파괴모드는 보강재 단면형상에 상관없이 보강재와 충전재가 하나로 거동하는 부착파괴 및 보강재 파단을 보였고, 홈 간격에 따라 홈 주변 콘크리트의 파괴면이 중첩되어 조기 부착파괴가 발생하는 것으로 나타났다. 등가 단면을 고려하여 부착상세를 개선한 기계적 맞물림(MI) 실험체의 파괴모드는 기존 부착파괴에서 CFRP 보강재 파단으로 개선되었고, CFRP 효율은 83%에서 100%로 향상되었다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2010년도 춘계 학술대회 제22권1호
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• pp.51-52
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• 2010

아치 작용과 트러스 작용의 관점에서 주근의 부착강도가 전단강도에 미치는 영향을 살펴본다. 부�T강도를 고려한 응력장으로 깊은 보와 얕은 보의 가능한 전단파괴의 종류를 구분할 수 있다. 또한 대각선 응력장의 기울기는 전단강도를 결정하는 응력전달 요소 중 2 개가 항복점에 도달할 ��의 균형점으로 해석할 수 있다.

• Structural Engineering and Mechanics
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• 제53권6호
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• pp.1083-1104
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• 2015

This paper provides the results of an experimental investigation into the flexural behavior of continuous two-span unbonded post-tensioned high strength concrete (HSC) beams, strengthened by end-anchored CFRP laminates of different configurations in the hogging region. Implementing two different configurations of end-anchorage systems consisting of steel plates and bolts and carefully monitoring the development of strains throughout the load history using sufficiently large number of strain gauges, the response of beams including the observed crack propagations, beam deflection, modes of failure, capacity enhancement at service and ultimate and the amount of moment redistribution are measured, presented and discussed. The study is appropriate in the sense that it covers the more commonly occurring two span beams instead of the simply supported beams investigated by others. The experiments reconfirmed the finding of others that proper installation of composite strengthening system is most important in the quality of the bond which is essential for the internal transfer of forces. It was also found that for the tested two span continuous beams, the capacity enhancement is more pronounced at the serviceability level than the ultimate. This is an important finding as the design of these beams is mostly governed by the serviceability limit state signifying the appropriateness of the suggested strengthening method. The paper provides quantitative data on the amount of this capacity enhancement.

• Steel and Composite Structures
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• 제27권5호
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• pp.537-543
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• 2018

Mechanical shear connectors are commonly used to transfer longitudinal shear forces across the steel-concrete interface in composite beams. Steel pipe as a new shear connector is proposed in this research and its performance to achieve composite strength is investigated. Experimental monotonic push-out tests were carried out for this connector. Then, a nonlinear finite element model of the push-out specimens is developed and verified against test results. Further, the finite element model is used to investigate the effects of pipe thickness, length and diameter on the shear strength of the connectors. The ultimate strengths of these connectors are reported and their respective failure modes are discussed. This paper comprises of the push-out tests of ten specimens on this shear connector in both the vertical and horizontal positions in different reinforced concretes. The results of experimental tests are given as load-deformation plots. It is concluded that the use of these connectors is very effective and economical in the medium shear demand range of 150-350 KN. The dominant failure modes observed were either failure of concrete block (crushing and splitting) or shear failure of pipe connector. It is shown that the horizontal pipe is not as effective as vertical pipe shear connector and is not recommended for practical use. It is shown that pipe connectors are more effective in transferring shear forces than channel and stud connectors. Moreover, based on the parametric study, a formula is presented to predict the pipe shear connectors' capacity.

• Steel and Composite Structures
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• 제46권1호
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• pp.75-92
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• 2023

The novel composite cold-formed steel (CFS)/engineered cementitious composites (ECC) beams have been recently presented. The new composite section exhibited superior structural performance as a flexural member, benefiting from the lightweight thin-walled CFS sections with improved buckling and torsional properties due to the restraints provided by thinlayered ECC. This paper investigated the shear performance of the new composite CFS/ECC section. Twenty-eight simply supported beams, with a shear span-to-depth ratio of 1.0, were assembled back-to-back and tested under a 3-point loading scheme. Bare CFS, composite CFS/ECC utilising ECC with Polyethylene fibres (PE-ECC), composite CFS/MOR, and CFS/HSC utilising high-strength mortar (MOR) and high-strength concrete (HSC) as replacements for PE-ECC were compared. Different failure modes were observed in tests: shear buckling modes in bare CFS sections, contact shear buckling modes in composite CFS/MOR and CFS/HSC sections, and shear yielding or block shear rupture in composite CFS/ECC sections. As a result, composite CFS/ECC sections showed up to 96.0% improvement in shear capacities over bare CFS, 28.0% improvement over composite CFS/MOR and 13.0% over composite CFS/HSC sections, although MOR and HSC were with higher compressive strength than PE-ECC. Finally, shear strength prediction formulae are proposed for the new composite sections after considering the contributions from the CFS and ECC components.

• 한국구조물진단유지관리공학회 논문집
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• 제12권6호
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• pp.89-96
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• 2008

본 연구에서는 탄소섬유판이 표면 매입된 철근 콘크리트 보의 휨 거동 효과를 고찰하였다. 이를 위하여, 탄소섬유판이 표면 매입된 T 형 철근 콘크리트 보를 제작하여 실험을 수행하였다. 본 연구 결과, 표면매입(NSM) 탄소섬유판으로 보강된 철근콘크리트 부재의 휨 강성 및 극한강도는 섬유판으로 보강되지 않은 보에 비하여 크게 증진되며, 그 최대 증가율은 보강되지 않은 부재의 경우보다 약 247%로 나타났다. 위 철근콘크리트 부재의 파괴는 부재 길이 방향으로 섬유 소선이 풀리는 표면매입 탄소 섬유판의 파괴로 시작되며, 탄소섬유판의 파단이 이어지는 2차 파괴가 발생하였다. 표면매입 탄소섬유판은 콘크리트와의 완정한 합성거동을 유도하여 따라서 탄소섬유판을 표면에 매입하는 방식은 노후 구조물 보강방식으로 매우 효과적인 것으로 판단된다.

• 한국구조물진단유지관리공학회 논문집
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• 제12권4호
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• pp.141-148
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• 2008

최근 건설 산업에서 CFRP는 재료적 장점들 때문에 구조물의 보강재로서 많이 사용되어 지고 있다. 본 논문에서 CFRP Plate가 보강된 철근콘크리트 보의 보강 효율과 설계 기초자료를 제공하려 한다. 정적 실험은 실험체의 파괴양상, 보강성능을 평가하였으며, 피로 실험은 처짐, 철근 변형률, CFRP Plate의 변형률을 분석하고, 에너지 소산과 보강성능을 평가하였다. 실험한 결과, 보강량이 증가할수록 단부 박리 파괴를 일으켰다. 그리고, 단부를 보강한 경우는 휨균열로 인한 박리파괴를 나타내는 파괴양상을 보였다. 피로 실험을 통하여 일정한 반복하중 횟수가 되면 처짐, 철근 변형률, CFRP Plate의 변형률 값이 일정한 값으로 수렴하였다. CFRP Plate가 보강된 보는 피로하중에 대해 사용성 확보가 가능했다.

• 한국강구조학회 논문집
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• 제21권6호
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• pp.647-657
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• 2009

본 연구는 강-프리스트레스 콘크리트(PSC) 혼합구조 보를 분절형 교량에 적용하기 위해 필수적으로 요구되는 이종 부재간의 연결에 대한 기초연구로써, 연결부 거동과 시공성을 향상시키기 위해 연결부 상․하부 플레이트에 perfobond rib 전단연결재를 설치한 강-PSC 연결부를 제안하였다. 제안된 연결부가 설치된 보 실험체들을 제작하여 하중재하실험을 통해 연결부의 성능을 확인한 결과, 모든 실험체에서 연결부의 파괴 없이 연결부 인접 PSC부에서 실험체의 파괴와 극한강도가 나타났다. 합성 작용에 의하여 실험체의 초기 강성은 우수한 것으로 나타났으며, 균열의 진전 형상도 전형적인 휨 균열 형상을 나타내었다. 또한, 기존 스터드를 적용한 실험체 이상의 강도를 얻을 수 있는 것으로 나타났다. 그러므로 제안된 연결부는 혼합구조 연결부에 효과적으로 적용 가능하다고 판단된다.

• International Journal of Concrete Structures and Materials
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• 제10권2호
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• pp.237-247
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• 2016

Progressive collapse resistance of RC buildings can be analyzed by considering column loss scenarios. Using finite element analysis and a static test, the progressive collapse process of a RC frame under monotonic vertical displacement of a side column was investigated, simulating a column removal scenario. A single-story 1/3 scale RC frame that comprises two spans and two bays was tested and computed, and downward displacement of a side column was placed until failure. Our study offers insight into the failure modes and progressive collapse behavior of a RC frame. It has been noted that the damage of structural members (beams and slabs) occurs only in the bay where the removal side column is located. Greater catenary action and tensile membrane action are mobilized in the frame beams and slabs, respectively, at large deformations, but they mainly happen in the direction where the frame beams and slabs are laterally restrained. Based on the experimental and computational results, the mechanism of progressive collapse resistance of RC frames at different stages was discussed further. With large deformations, a simplified calculation method for catenary action and tensile membrane action is proposed.

• Steel and Composite Structures
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• 제27권5호
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• pp.545-554
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• 2018

This study presents a novel method of improving the strength and stiffness of cold-formed steel (CFS) beams. Flexural members are primary members in most of the structures. Hence, there is an urgent need in the CFS industry to look beyond the conventional CFS beam sections and develop novel techniques to address the severe local buckling problems that exist in CFS flexural members. The primary objective of this study was to develop new CFS composite beam sections with improved structural performance and economy. This paper presents an experimental study conducted on different CFS composite beams with simply supported end conditions under four point loading. Material properties and geometric imperfections of the models were measured. The test strengths of the models are compared with the design strengths predicted by using Australian/New Zealand Standard for cold-formed steel structures. Furthermore, to ensure high precision testing, a special testing rig was also developed for testing of long span beams. The description of test models, testing rig features and test results are presented here. For better interpretation of results, a comparison of the test results with a hot rolled section is also presented. The test results have shown that the proposed CFS composite beams are promising both in terms of better structural performance as well as economy.