• Structural Engineering and Mechanics
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• 제81권5호
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• pp.551-563
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• 2022

Bolted connector could be an alternative to replace the conventional welded headed stud in steel-ultra high performance concrete (UHPC) lightweight composite structures. In this paper, a novel demountable bolted shear connector, consisting of a high-strength bolt (HSB) and a specially-designed nut which is pre-embedded in a thin UHPC slab, is proposed, which may result in the quick installation and disassembly, due to the mountable, demountable and reusable features. In order to study the shear behavior of the new type of bolted shear connector, static push-out tests were conducted on five groups of the novel demountable bolted shear connector specimens and one group of conventional welded headed stud specimen for comparison. The effect of the bolt shank diameter and aspect ratio of bolt on failure mode, shear stiffness, peak slip at the steel-UHPC interface, shear strength and ductility of novel bolted connectors is investigated. Additionally, design formula for the shear strength is proposed to check the suitability for assessment of the novel demountable bolted shear connectors.

• 한국건설순환자원학회논문집
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• 제10권4호
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• pp.376-385
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• 2022

국민의 안전과 편의성에 직결되는 도로 인프라인 PSC거더교의 바닥판 손상 및 노후화로 인한 교체공사를 대비하여 매립형 분리식 전단연결재가 개발되었다. 분리식 전단연결재는 바닥판 철거 공정에서 파쇄를 최소화하고 교체공사를 위한 전단연결재 재시공이 용이하여 시공성 향상으로 인한 공사기간 감소로 도로이용자의 불편과 손실을 최소화할 수 있다. 공법별 공사기간과 공사기간 중 교통차단으로 인해 발생하는 도로이용자비용을 산출하여 비교하는 방법으로 기존 공법 대비 매립형 분리식 전단연결재를 적용한 PSC거더교의 경제성을 도로이용자(국민) 입장에서 분석하였다. 매립형 분리식 전단연결재가 적용된 교량 바닥판 교체공사 시 도로이용자비용은 34일 1,404,687,725원으로 기존 ∩형태 전단철근 노출 전단연결재가 적용된 경우(54일, 1,924,740,367원) 대비 공사기간 20일, 도로이용자비용 27.02 %를 절감할 수 있는 것으로 분석되었다.

• 대한토목학회논문집
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• 제42권6호
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• pp.751-762
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• 2022

강합성 교량에서 강 거더와 콘크리트 바닥판의 합성을 위한 전단연결재로는 용접접합 머리붙이 스터드가 주로 사용된다. 용접접합 전단연결재의 경우, 손상 또는 노후화된 바닥판 철거 시에 파쇄에 따른 소음, 비산먼지 등이 발생하여 환경적 문제가 지적되고 있다. 따라서 환경적 문제 및 생애주기비용 관점의 효율적인 유지관리를 위해서는 노후화된 콘크리트 바닥판의 교체가 용이한 분리식 전단연결재 개발이 필요하다. 기존의 볼트접합 전단연결재로는 매립너트 방식이 주로 연구되었으나 낮은 강성과 전단저항강도, 초기슬립 증가 등으로 교량과 같은 토목구조물에는 활용되지 못하고 있는 실정이다. 본 논문에서는 이러한 문제점들을 개선하기 위해 매립너트 부분이 스터드 기둥에 일체화되고 확대 기둥 하단에 테이퍼진 형상을 갖는 분리식 볼트접합 전단연결재를 제안하였다. 제안된 분리식 스터드볼트의 정적 전단강도와 슬립 변위에 대한 성능 검증을 위해 수평전단실험을 수행하였고, 기존 용접접합 스터드와 성능을 비교하였다. 제안된 분리식 볼트접합 전단연결재가 전단성능이 매우 우수하고, 슬립변위 또한 연성설계기준을 만족함으로써 기존 용접 스터드를 충분히 대체하여 적용 가능함을 확인하였다.

• Steel and Composite Structures
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• 제43권4호
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• pp.419-429
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• 2022

In response to the sustainability requirements set in the EU Commission's "Green Deal" towards reduction of the greenhouse gas emissions, it is estimated that the structural design for deconstruction is going to contribute considerably to the sustainable development of the built environment. The demountability of multi-material structural systems basically depends on the shear connectors used in the structural system. This paper focuses on a type of demountable injected shear connector with an injected steel-reinforced resin (iSRR) which consists of spherical steel particles embedded in a resin. Its application to steel-to-concrete and steel-to-Fiber Reinforced Polymer (FRP) decks is presented along with its benefits. In parallel, an overview of the experimental and numerical research on the evaluation of the mechanical properties of the demountable bolted connectors with iSRR is discussed. Last, detailed finite element (FE) models and a parametric study are performed to quantify the confinement level of the SRR material influenced by the oversized hole diameter.

• Steel and Composite Structures
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• 제45권6호
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• pp.797-818
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• 2022

Steel-precast ultra-high-performance concrete (UHPC) composite beams with demountable high-strength friction-grip bolt (HSFGB) shear connectors can be used for accelerated bridge construction (ABC) and achieve excellent structural performance, which is expected to be dismantled and recycled at the end of the service life. However, no investigation focuses on the demountability and reusability of such composite beams, as well as the installation difficulties during construction. To address this issue, this study conducted twelve push-out tests to investigate the effects of assembly condition, bolt grade, bolt-hole clearance, infilling grout and pretension on the crack pattern, failure mode, load-slip/uplift relationship, and the structural performance in terms of ultimate shear strength, friction resistance, shear stiffness and slip capacity. The experimental results demonstrated that the presented composite beams exhibited favorable demountability and reusability, in which no significant reduction in strength (less than 3%) and stiffness (less than 5%), but a slight improvement in ductility was observed for the reassembled specimens. Employing oversized preformed holes could ease the fabrication and installation process, yet led to a considerable degradation in both strength and stiffness. With filling the oversized holes with grout, an effective enhancement of the strength and stiffness can be achieved, while causing a difficulty in the demounting of shear connectors. On the basis of the experimental results, more accurate formulations, which considered the effect of bolt-hole clearance, were proposed to predict the shear strength as well as the load-slip relationship of HSFGBs in steel-precast UHPC composite beams.

• Steel and Composite Structures
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• 제36권3호
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• pp.321-337
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• 2020

Contemporary design and construction of steel-concrete composite structures employs the use of prefabricated concrete elements and demountable shear connectors in order to reduce the construction time and costs and enable dismantling of elements for their potential reuse at the end of life of buildings. Bolted shear connector with mechanical coupler is presented in this paper. The connector is assembled from mechanical coupler and rebar anchor, embedded in concrete, and steel bolt, used for connecting steel to concrete members. The behaviour and ultimate resistance of bolted connector with mechanical coupler in wide and narrow members were analysed based on push-out tests and FE analyses conducted in Abaqus software, with focus on concrete edge breakout and bolt shear failure modes. The effect of concrete strength, concrete edge distance and diameter and strength of bolts on failure modes and shear resistance was analysed. It was demonstrated that premature failure by breakout of concrete edge occurs when connectors are located 100 mm or closer from the edge in low-strength and normal-strength reinforced concrete. Furthermore, the paper presents a relatively simple model for hand calculation of concrete edge breakout resistance when bolted connectors with mechanical coupler are used. The model is based on the modification of prediction model used for cast-in and post-installed anchors loaded parallel to the edge, by implementing equivalent influence length of connector with variable diameter. Good agreement with test and FE results was obtained, thus confirming the validity of the proposed method.