• 한국구조물진단유지관리공학회 논문집
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• 제27권1호
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• pp.71-77
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• 2023

이 연구에서는 높이가 400 mm인 중공슬래브(Hollow-Core Slab, 이하 HCS)의 구조성능을 평가하기 위한 실대형 실험을 수행하였으며, 기존의 압출성형방식이 아닌 단일몰드방식을 적용하여 총 4개의 HCS를 제작하였다. 실험의 주요 변수는 토핑콘크리트의 유무, 전단보강근의 배치 유무 및 위치로 설정하였으며, 실험체들의 균열패턴 및 하중-변위 응답을 상세히 분석하였다. 실험결과 전단철근이 배치된 HCS 실험체들은 휨강도를 달성하였고, 이후에 최종적인 파괴는 사인장균열에 의하여 지배되었으며, HCS 유닛 웨브 내에 전단철근이 배치되지 않은 실험체들의 경우 설계기준을 통해 산정된 공칭휨강도를 발현하지 못하였다. 전단철근을 HCS 유닛에 배근 할 경우에는 전단강도가 약 8~23% 증가하는 것으로 나타났으며, HCS의 중공을 철근콘크리트로 보강하는 방법보다 전단성능 향상에 더 효과적인 것으로 나타났다.

• 콘크리트학회논문집
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• 제26권6호
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• pp.741-749
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• 2014

프리스트레스트 중공(PHC) 슬래브는 장경간에 적합하도록 경량화된 효율적인 프리캐스트 부재이며, 국내 외에서 많이 사용되고 있다. 특히, 국내에서는 현장타설콘크리트와 같이 사용되는 합성슬래브 형태로 주로 적용되고 있다. 그러나, 압출성형방식으로 제작되는 PHC 슬래브 부재는 매우 낮은 슬럼프의 콘크리트로 제작되어 타설 직후에도 표면경도가 높기 때문에 계면의 거친면 처리 및 전단연결재 배치가 어려운 단점이 있다. 이 연구에서는 PHC slab 부재와 토핑콘크리트 사이의 합성성능을 고찰하기 위하여 다양한 계면상태를 변수로 직접전단실험을 수행하였으며, 기존 실험결과를 수집하여 국내 외 수평전단강도 설계기준을 평가하였다.

• 한국강구조학회 논문집
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• 제20권4호
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• pp.493-504
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• 2008

본 연구는 속빈 PC 슬래브와 채널을 사용한 매입형 합성보의 휨거동에 관한 것이다. 철골보와 PC슬래브의 경계면에 발생하는 전단력은 채널에 의해서 전달된다. 철골보의 춤에 따라서 총 3개의 실대형 실험체를 제작하여 실험을 수행하였으며 기존에 수행된 전단접합 방식과 비교검토를 수행하였다. 채널 용접형 매입형 합성보의 실험결과, 별도의 전단연결재를 설치하지 않아도 자체가 가지고 있는 기계적․화학적 부착응력으로 인해 완전합성보에 가까운 거동을 나타내었다. 또한, 기존의 합성보의 거동과 같이 탄성구간, 항복구간, 매우 큰 연성, 휨파괴모드(소성힌지), 경계면에서의 매우 낮은 상대슬립 및 연성적인 파괴거동을 나타내었다. 따라서 제안된 전단연결 방식의 경우, 실제 건물에 적용시 규준에서 요구하는 구조적 성능을 만족할 수 있는 것으로 나타났다.

• Computers and Concrete
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• 제28권5호
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• pp.497-506
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• 2021

Steel-concrete composite structures and precast concrete elements have a common prefabrication process and allow fast construction. The use of hollow-core slabs associated with composite floors can be advantageous. However, there are few studies on the subject, impeding the application of such systems. In this paper, a numerical model representing the considered system using the FE (finite element)-based software DIANA is developed. The results of an experimental test were also presented in Souza (2016) and were used to validate the model. Comparisons between the numerical and test results were performed in terms of the load versus displacement, load versus slip, and load versus strain curves, showing satisfactory agreement. In addition, a wide parametric study was performed, evaluating the influence of several parameters on the behaviour of the composite system: The strength of the steel beam, thickness of the web, thickness and width of the bottom flange of the steel beam and concrete cover thickness on top of the beam. The results indicated a great influence of the steel strength and the thickness of the bottom flange of the steel beam on the capacity of the composite floor. The remaining parameters had limited influences on the results.

• Computers and Concrete
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• 제14권3호
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• pp.211-231
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• 2014

Prestressed hollow-core slabs (HCS) are widely used for modern lightweight precast floor structures because they are cost-efficient by reducing materials, and have excellent flexural strength and stiffness by using prestressing tendons, compared to reinforced concrete (RC) floor system. According to the recently revised ACI318-08, the web-shear capacity of HCS members exceeding 315 mm in depth without the minimum shear reinforcement should be reduced by half. It is, however, difficult to provide shear reinforcement in HCS members produced by the extrusion method due to their unique concrete casting methods, and thus, their shear design is significantly affected by the minimum shear reinforcement provision in ACI318-08. In this study, a large number of shear test data on HCS members has been collected and analyzed to examine their web-shear capacity with consideration on the minimum shear reinforcement requirement in ACI318-08. The analysis results indicates that the minimum shear reinforcement requirement for deep HCS members are too severe, and that the web-shear strength equation in ACI318-08 does not provide good estimation of shear strengths for HCS members. Thus, in this paper, a rational web-shear strength equation for HCS members was derived in a simple manner, which provides a consistent margin of safety on shear strength for the HCS members up to 500 mm deep. More shear test data would be required to apply the proposed shear strength equation for the HCS members over 500 mm in depth though.

• Steel and Composite Structures
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• 제29권1호
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• pp.1-22
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• 2018

Multi-storey precast concrete skeletal structures are assembled from individual prefabricated components which are erected on-site using various types of connections. In the current design of these structures, beam-to-column connections are assumed to be pin jointed. Welded plate beam to-column connections have been used in the precast concrete industry for many years. They have many advantages over other jointing methods in component production, quality control, transportation and assembly. However, there is at present limited information concerning their detailed structural behaviour under bending and shear loadings. The experimental work has involved the determination of moment-rotation relationships for semi-rigid precast concrete connections in full scale connection tests. The study reported in this paper was undertaken to clarify the behaviour of such connections under symmetrical vertical loadings. A series of full-scale tests was performed on sample column for which the column geometry and weld arrangements conformed with successful commercial practice. Proprietary hollow core slabs were tied to the beams by tensile reinforcing bars, which also provide the in-plane continuity across the connections. The strength of the connections in the double sided tests was at least 0.84 times the predicted moment of resistance of the composite beam and slab. The secant stiffness of the connections ranged from 0.7 to 3.9 times the flexural stiffness of the attached beam. When the connections were tested without the floor slabs and tie steel, the reduced strength and stiffness were approximately a third and half respectively. This remarkable contribution of the floor strength and stiffness to the flexural capacity of the joint is currently neglected in the design process for precast concrete frames. In general, the double sided connections were found to be more suited to a semi-rigid design approach than the single sided ones. The behaviour of double sided welded plate connection test results are presented in this paper. The behaviour of single sided welded plate connection test results is the subject of another paper.

• Steel and Composite Structures
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• 제29권5호
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• pp.603-622
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• 2018

Precast concrete structures are erected from individual prefabricated components, which are assembled on-site using different types of connections. In the present design of these structures, beam-to-column connections are assumed pin jointed. Bolted billet beam to-column connections have been used in the precast concrete industry for many years. They have many advantages over other jointing methods in component production, quality control, transportation and assembly. However, there is currently limited information concerning their detailed structural behaviour under vertical loadings. The experimental work has involved the determination of moment-relative rotation relationships for semi-rigid precast concrete connections in full-scale connection tests. The study reported in this paper was undertaken to clarify the behaviour of such connections under symmetrical vertical loadings. A series of full-scale tests was performed on sample column for which the column geometry and bolt arrangements conformed to successful commercial practice. Proprietary hollow core floor slabs were tied to the beams by 2T25 tensile reinforcing bars, which also provide the in-plane continuity across the connections. The contribution of the floor strength and stiffness to the flexural capacity of the joint is currently neglected in the design process for precast concrete frames. The flexural strength of the connections in the double-sided tests was at least 0.93 times the predicted moment of resistance of the composite beam and slab. The secant stiffness of the connections ranged from 0.94 to 1.94 times the flexural stiffness of the attached beam. In general, the double-sided connections were found to be more suited to a semi-rigid design approach than the single sided ones. The behaviour of double sided bolted billet connection test results are presented in this paper. The behaviour of single sided bolted billet connection test results is the subject of another paper.

• Steel and Composite Structures
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• 제46권4호
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• pp.451-469
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• 2023

The use of precast hollow-core slabs (PCHCS) in civil construction has been increasing due to the speed of execution and reduction in the weight of flooring systems. However, in the literature there are no studies that present a finite element model (FEM) to predict the load-slip relationship behavior of pushout tests, considering headed stud shear connector and PCHCS placed at the upper flange of the downstand steel profile. Thus, the present paper aims to develop a FEM, which is based on tests to fill this gap. For this task, geometrical non-linear analyses are carried out in the ABAQUS software. The FEM is calibrated by sensitivity analyses, considering different types of analysis, the friction coefficient at the steel-concrete interface, as well as the constitutive model of the headed stud shear connector. Subsequently, a parametric study is performed to assess the influence of the number of connector lines, type of filling and height of the PCHCS. The results are compared with analytical models that predict the headed stud resistance. In total, 158 finite element models are processed. It was concluded that the dynamic implicit analysis (quasi-static) showed better convergence of the equilibrium trajectory when compared to the static analysis, such as arc-length method. The friction coefficient value of 0.5 was indicated to predict the load-slip relationship behavior of all models investigated. The headed stud shear connector rupture was verified for the constitutive model capable of representing the fracture in the stress-strain relationship. Regarding the number of connector lines, there was an average increase of 108% in the resistance of the structure for models with two lines of connectors compared to the use of only one. The type of filling of the hollow core slab that presented the best results was the partial filling. Finally, the greater the height of the PCHCS, the greater the resistance of the headed stud.

• 콘크리트학회논문집
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• 제28권1호
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• pp.3-11
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• 2016

건물의 자중을 저감시킴으로서 시공성을 향상시키기 위한 방안으로 중공 PC슬래브에 대한 관심이 높아지고 있다. 이와 같은 측면에서, 최근 새로운 형태의 부분 PC 슬래브 시스템인 Tripple Ribs Slab (TRS)가 개발되었다. TRS부재는 3개의 리브와 스트랜드로 프리스트레싱된 바닥구조로 구성되어 있다. TRS 바닥구조는 웨브와 웨브 사이에 스티로폼(styrofoam)을 채운 뒤 토핑 콘크리트를 타설함으로서 슬래브 시스템을 구축한다. 본 연구에서는 TRS의 휨성능을 검토하기 위해 휨실험을 진행하였다. Full scale로 제작된 5개의 실험체를 제작한 뒤 휨파괴되도록 단순지지조건으로 실험하였으며 실험결과 강도를 기준 식들과 비교하였다. 실험에서의 변수는 부재의 깊이와 토핑 또는 슬립포밍시 형성되는 추가의 콘크리트 턱의 유무이다. 또한 실험체들에 대하여 비선형 단면해석을 실시하였으며 그 결과를 실험결과와 비교하였다. 실험으로부터, TRS는 설계하중을 충분히 지지할 수 있는 휨성능과 연성능력을 가지고 있으며 실험체의 강도는 기준 식으로 적절하게 예측될 수 있는 것으로 나타났다. 추가의 턱은 실험체의 강도에 영향을 미치지 못하는 것으로 나타났으며 이에 따라 이들 턱은 굳이 추가의 작업을 통하여 제거할 필요는 없는 것으로 사료된다. 비선형 단면해석을 통하여 TRS의 휨거동을 보다 정확하게 예측하기 위해서는 슬립포밍에 의한 콘크리트의 취성적인 특성을 해석에서 고려할 필요가 있는 것으로 판단된다.