• Journal of the Korea Concrete Institute
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• v.25 no.1
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• pp.81-90
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• 2013

The purpose of this study is to evaluate the horizontal shear strength on the interface between PC and cast-in-place concrete for PC composite beams. Six specimens were tested to examine the structural performance of the horizontal interface with different surface condition and stirrup detailing. Except for SF-291B specimen failed in flexural compression, strengths and deformation capacities of five specimens were determined by horizontal shear failure. Horizontal shear strengths by composite horizontal shear or shear friction in current codes could be used to predict the horizontal shear capacity of the interface for specimens. Also detailing for stirrup by PCI design provision could be used to accomplish the composite action in the interface.

• Journal of the Korea institute for structural maintenance and inspection
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• v.11 no.4
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• pp.99-108
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• 2007

In the flat-plate slab design of the KCI and ACI building code, the punching shear strength of connections with shear reinforcement can increase one and half times to that of connections without shear reinforcement. And the ACI-ASCE committee 352 recommendations propose limiting the direct shear ratio $V_g$/$V_c$ on interior connections to 0.4 to insure adequate drift capacity. In this study, four interior column-slab connections were tested to look into the punching shear strength and the lateral displacement capacity of the flat-plate slab with and without shear reinforcement under cyclic lateral loading. Based on the test results, it is found that the provision about punching shear strength in the codes may appropriate for the gravity loading only whereas it is unconservative for the lateral loading and that the limit of ACI-ASCE committee 352 appears conservative.

• Journal of the Korea Concrete Institute
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• v.23 no.2
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• pp.235-244
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• 2011

Failures of segmental bridges have been attributed to the inadequate joint connection techniques, which led to corrosion of the post-tensioned tendons connecting the segmental joints. The principal objective of this study is to evaluate the performances of the in-situ cast joint and epoxy applied shear key joints as a function of shear and ultimate strengths. Furthermore, shear behavior and strength of shear key joints in ultra high performance precasted concrete segmental bridges are experimentally evaluated to understand its shear failure behavior. The test parameters of shear key shape and type, load-displacement relations, cracking behavior, concrete strength, and fracture modes are considered in the study. Also, several parameters which influence the mechanical behavior of the shear key joint are analyzed. Based on the study results, the optimal shear key shape and joint type are proposed for the joint design and analysis guidelines.

• Journal of the Korea Concrete Institute
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• v.22 no.3
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• pp.345-356
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• 2010

An alternative design method for interior flat plate-column connections subjected to punching shear and unbalanced moment was developed. Since the slab-column connections are severely damaged by flexural cracking before punching shear failure, punching shear was assumed to be resisted mainly by the compression zone of the slab critical section. Considering the interaction with the flexural moment of the slab, the punching shear strength of the compression zone was evaluated based on the material failure criteria of concrete subjected to multiple stresses. The punching shear strength was also used to evaluate the unbalanced moment capacity of the slab-column connections. For verification, the proposed strength model was applied to existing test specimens subjected to direct punching shear or combined punching shear and unbalanced moment. The results showed that the proposed method predicted the strengths of the test specimens better than current design methods in ACI 318 and Eurocode 2.

• 한국방재학회:학술대회논문집
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• 2011.02a
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• pp.32-32
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• 2011

최근 국내외에서 친환경건축물에 관한 관심이 매우 높아짐으로 인해 콘크리트의 물량을 절감하여 이산화탄소량을 줄이는 중공슬래브는 다양한 형태로 세계적으로 개발이 되고 있는 추세이다. 특히 이방향 중공슬래브는 환경적인 측면에서 이방향 중공슬래브는 중공부 생성에 재생플라스틱을 활용하여 폐자원을 재사용하고, 콘크리트와 철근의 사용량 절감에 따른 화석에너지 및 이산화탄소 발생량을 감소한다는 장점이 있다. 또한 시스템 측면에서 이방향 중공슬래브는 기존의 철근콘크리트 플랫플레이트 바닥구조 시스템의 자중을 절감하여 구조체를 경량화 시키고, 이에 따라 장스팬 구현이 가능하며, 단열효과가 뛰어나다. 이와 같이 이방향 중공슬래브는 장점이 많지만 플랫플레이트 슬래브의 취약점인 뚫림전단 파괴에 주의해야 한다. 이에 본 연구에서는 선행으로 실시된 이방향 중공슬래브-기둥 접합부 뚫림전단 성능평가 실험을 바탕으로 하여 경량체가 이방향 중공슬래브-기둥 접합부 뚫림전단 성능에 미치는 영향을 살펴보기 위해 범용 유한요소해석 프로그램인 ABAQUS를 사용하여 경량체량 및 위치를 주요변수로 한 해석적인 변화를 검토하였다. 본 연구를 통해 경량체가 삽입된 이방향 중공슬래브의 뚫림전단 성능에 대해, 해석결과 경량체 량과 위치에 따라 최대 뚫림전단강도는 기준 실험체에 비해 74.3%, 73%의 강도저하를 나타내는 것으로 알 수 있었다. 이는 실험상의 강도저하 값인 84.1%, 56.4%와 다소 차이가 있으며, 해석에서 중공부 주위의 응력집중 현상이 제대로 반영되지 않은 것으로 판단된다. 또한 이방향 슬래브에 경량체를 삽입 할 경우 경량체가 시작하는 부분에서 응력이 급격히 감소하는 현상이 나타났으며, 이러한 급격한 응력감소는 기둥 주위 위험단면의 변화를 가져오는 것으로 추정된다. 즉, 위험단면의 변화는 기둥으로부터 경량체 사이의 거리에 따라 달라지며, 위험단면 내의 콘크리트 단면 손실은 뚫림전단 강도를 감소시킨다. 본 연구에서는 이방향 중공슬래브의 뚫림전단강도를 산정할 수 있는 근사식을 제안하였으며, 보다 정확한 이방향 중공슬래브의 뚫림전단강도의 산정식을 위해서는 위험단면의 변화와 콘크리트 단면손실로 인한 전단강도 저하의 관계에 대한 추가적인 연구가 필요하다.

• Journal of Korean Society of Steel Construction
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• v.24 no.4
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• pp.423-433
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• 2012

This paper summarizes full-scale gravity-load test results on CFT column-to-RC flat plate connections reinforced with shearhead. CFT construction has many structural and constructional advantages over conventional steel and RC column construction and is gaining wide acceptance. Meanwhile the use of RC flat plate system in the basement and residential floors of tall buildings is often mandatory to reduce story height and enable rapid construction in domestic practice. Combining CFT column and flat plate floor is expected to result in further rapid construction. However, the issues related to connecting CFT column to RC flat plate have not been fully addressed yet. Several promising connecting schemes by using steel shearhead were proposed and tested in this study. Test results showed that the proposed connection can exhibit the punching shear strength higher than RC flat plate counterparts. An empirical formula that can reasonably predicts the punching shear strength of the proposed connection was also proposed.

• Journal of the Korea institute for structural maintenance and inspection
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• v.11 no.4
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• pp.62-70
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• 2007

This paper reports an evaluation method on the shear strength of interior beam-column joints composed of steel beams and reinforced concrete columns(RCS). The shear strength is generally calculated by the sum of the nominal shear resistance of a steel web panel and concrete elements. In this paper, the shear strength is calculated based on the compression strut theory instead of compression field theory. Design equations presented herein are evaluated through comparison with existing experimental results. The comparisons between experimental and calculated results show an excellent agreement.

• Journal of the Korea institute for structural maintenance and inspection
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• v.10 no.1
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• pp.97-105
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• 2006

The reinforced concrete flat plate system provides architectural flexibility, clear space, reduced building height, simple formwork, which consequently enhance constructibility. One of the serious problem in the flat plate system is brittle punching shear failure due to transfer of shear force and unbalanced moments in column-slab connection. Since the use of high strength concrete recently has become in practice for reinforced concrete structures, it is highly desired to establish the structural design method for flat plate construction using high strength concrete. In this paper, interior column-slab connection constructed with high strength concrete were tested under lateral and gravity loads to evaluate their strength and behavior. The test parameters were slab reinforcement ratio and the gravity load levels.

• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.6
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• pp.156-165
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• 2011

This study investigates the horizontal shear behavior of an interface between precast concrete (PC) and topping concrete(RC), and evaluates the horizontal based on the investigations by the experimental. Horizontal shear strength in connected surface is determined by the roughness an interface and the shear reinforcement or not. In this study, the main experimental parameters are the shear reinforcement types in the shape of loop-type and lattice-type, rebar spacing. A total of four specimens were shear strength tested and manufactured. As a result, the horizontal shear strength of reinforced connected surface was found to be controlled by deformation in vertical direction. Comparison of reinforcement shape, the mean initial crack load loop type specimens, the average maximum load and the junction of the average in terms of initial stiffness, respectively 33.7%, 45.9% and 55.2% were large enough. Evaluation results for shear strength equation of existing standard domestic, the loop-type reinforced 2.32 to 4.23 times, lattice-type reinforced 1.65 to 3.06 times appears to be higher. Behavior of interface or strength of structural design criteria was fairly safe side. It does not have any problems in the applied field is considered.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.05a
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• pp.56.2-56.2
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• 2011

최근 철강, 알루미늄, 이종재료의 접합 등 용접이 어려운 부분에 구조용 접착제의 적용이 증가하고 있는 추세이다. 이를 위해 변성 에폭시레진을 활용한 고접합 강도, 고인성의 구조용 접착제가 연구되어 지고 있다. 피착제의 표면처리는 접합부의 접합강도를 향상시키는 방법으로 알려져 있으나 최근의 구조용 접착제는 표면 전처리 없이도 우수한 접착 특성을 보이는 것으로 기대되고 있다. 본 연구에서는 변성레진에 대해서 각종 표면처리가 접합부 특성에 미치는 영향을 조사하였다. 피착제로는 자동차용 냉연강판인 SPRC440을 사용하였고, 전처리로는 무처리 상태, SiC연마지를 이용한 연마, 아르곤 및 산소가스를 이용한 마이크로웨이브 플라즈마 표면처리, 산세 등의 표면처리를 실시하였다. 에폭시 접착제는 변성 에폭시 레진과 경화제 및 촉매제를 이용하여 직접 포뮬레이션하였다. 단일 겹치기 전단강도 시험과 T-Peel 시험은 각각 ASTM D 1002 규격에 따라 준비하였으며 인장 시험 후 파면은 SEM으로 관찰하였다.