• 한국구조물진단유지관리공학회 논문집
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• 제16권5호
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• pp.88-97
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• 2012

본 연구에서는 비내진 교각의 내진성능과 휨-전단 거동을 파악하고자 형상비 4.5인 정사각형의 중실 및 중공단면 철근콘크리트 교각실험체를 제작하여 일정한 축력하에서 변위비 등급을 증가시켜 가면서 횡하중을 가력하는 실험을 수행하였다. 본 연구는 철근콘크리트 교각의 한정연성 내진설계를 위한 실험적 기초자료의 제공과 함께 성능단계별 교각성능 및 손상평가를 위한 정량적 수치와 경향을 제공하기 위한 것이며, 파괴거동, 극한변위, 극한드리프트비율, 변위연성도, 응답수정계수, 등가점성감쇠비, 잔류변형지수, 유효강성, 철근 변형률 등의 주요 내진성능 인자들에 대한 분석결과와 비선형 해석 결과를 나타내었다.

• 한국공간구조학회논문집
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• 제15권1호
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• pp.57-64
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• 2015

This paper shows the test results of continuous reinforced concrete beams with external post-tensioning rods. Six three-span beams were prepared and tested to fail. Three beams were designed to have flexure-dominating behavior and the others to have shear-critical behavior. In each group, one beam without external post-tensioning rods was designated as a control beam and two beams had the external post-tensioning rods of 18 mm or 22 mm diameter. External post-tensioning rods were installed within an interior span of 6000 mm. They show V-shaped configuration because two anchorages were located at the top of interior supports and a saddle pin at mid-span was installed at the bottom of the beam. Test results show that the load and shear capacities of strengthened beams were increased when compared with the control beam. Additionally, the measured shear strength was compared with the strength predicted by ACI 318-11 code equations. The detailed ACI 318-11 equation predicted the measured shear strength and failure location of the continuous beam reasonably well.

• 한국산학기술학회논문지
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• 제16권6호
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• pp.4245-4252
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• 2015

유리섬유강화폴리머(GFRP) 판을 현장타설 고강도콘크리트 구조물의 영구거푸집으로 사용하기 위한 실험을 수행하였다. 현재 생산되는 GFRP 판의 경우 표면이 매끈하여 콘크리트와 일체 거동에 다소 문제점을 갖고 있다. 따라서 본 연구에서는 GFRP 판 하부의 잔골재 부착여부, GFRP판 웨브의 천공유무 및 간격, 상부 플랜지 폭을 실험 변수로 하여 현장타설 고강도콘크리트와 GFRP를 영구거푸집으로 활용한 전단경간비가 짧은 합성보의 휨/전단파괴거동을 분석하였다. GFRP 판 웨브를 천공하지 않은 경우 잔골재 부착효과 여부를 위한 실험 결과, 잔골재를 부착한 경우 미부착의 경우 보다 약 47% 정도의 높은 극한하중 값을 보여주며, 파괴형태도 휨/전단파괴모드를 보여 주었다. 웨브의 천공유무 및 간격효과는 잔골재를 부착하지 않은 경우 천공간격이 조밀한 경우가 약 24% 정도 높은 극한하중 값을 보여주었으며, 잔골재를 부착한 경우 천공 간격이 조밀하지 않은 경우가 약 25% 정도 낮은 극한하중 값을 보여주었다. 상부플랜지 영향을 살펴보면, 폭 40mm 경우가 20mm에 비해 약 17% 정도 큰 극한하중 값을 보여주었다.

• International Journal of Concrete Structures and Materials
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• 제10권3호
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• pp.297-306
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• 2016

This paper developed an analytical software, called Simulation of Concrete Structures (SCS), which is used for numerical analysis of shear-critical prestressed steel fiber concrete structures. Based on the previous research at the University of Houston (UH), SCS has been derived from an object-oriented software framework called Open System for Earthquake Engineering Simulation (OpenSees). OpenSees was originally developed at the University of California, Berkeley. New module has been created for steel fiber concrete under prestress based on the constitutive relationships of this material developed at UH. This new material module has been integrated with the existing material modules in OpenSees. SCS thus developed has been used for predicting the behavior of the prestressed steel fiber concrete I-beams and Box-beams tested earlier in this research. The analysis could well predict the entire behavior of the beams including the elastic stiffness, yield point, post-yield stiffness, and maximum load for both web shear and flexure shear failure modes.

• Earthquakes and Structures
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• 제21권5호
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• pp.505-514
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• 2021

A formulation based on structural reliability and cost effectiveness is proposed to provide recommendations to select the best retrofit strategy for schools with reinforced concrete frames and masonry walls, among three proposed alternatives. The cost calculation includes the retrofit cost and the expected costs of failure consequences. Also, the uncertainty of the seismic hazard is considered for each school site. The formulation identifies the potential failure modes, among shear and bending forces for beams, and flexure-compression forces for columns, for each school, and the seismic damages suffered by the schools after the earthquake of September 17, 2017 are taken into account to calibrate the damaged conditions per school. The school safety level is measured through its global failure probability, instead of only the local failure probability. The proposed retrofit alternatives are appraised in terms of the cost/benefit balance under future earthquakes, for the respective site seismic hazard, as opposed to the current practice of just restoring the structure original resistance. The best retrofit is the one that corresponds to the minimum value of the expected life cycle cost. The study, with further developments, may be used to develop general recommendations to retrofit schools located at seismic zones.

• 한국지진공학회논문집
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• 제24권1호
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• pp.39-47
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• 2020

Lightly reinforced concrete (RC) moment frames may suffer significant damage during large earthquake events. Most buildings with RC moment frames were designed without considering seismic loads. The load-displacement response of gravity load designed frames could be altered by masonry infill walls. The objective of this study is to investigate the load-displacement response of gravity load designed frames with masonry infill walls. For this purpose, three-story gravity load designed frames with masonry infill walls were considered. The masonry infilled RC frames demonstrated larger lateral strength and stiffness than bare RC frames, whereas their drift capacity was less than that of bare frames. A specimen with a partial-height infill wall showed the least drift capacity and energy dissipation capacity. This specimen failed in shear, whereas other specimens experienced a relatively ductile failure mode (flexure-shear failure).

• International Journal of Concrete Structures and Materials
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• 제9권1호
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• pp.69-88
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• 2015

Self-consolidating concrete (SCC) is a stable and cohesive high consistency concrete mix with enhanced filling ability properties that reduce the need for mechanical compaction. Limited standards and specifications have been reported in the literature on the structural behavior of reinforced self-compacting concrete elements. The significance of the research presented in this paper stems from the need to investigate the effect of enhanced fluidity of SCC on the structural behavior of high strength self-consolidating reinforced concrete beams. To meet the objectives of this research, twelve reinforced concrete beams were prepared with two different generations of superplasticizers and designed to exhibit flexure, shear, or bond splitting failure. The compared beams were identical except for the type of superplasticizer being used (second generation sulphonated-based superplasticizer or third generation polycarboxylate-based superplasticizer). The outcomes of the experimental work revealed comparable resistance of beam specimens made with self-compacting (SCC) and conventional vibrated concrete (VC). The dissimilarities in the experimental values between the SCC and the control VC beams were not major, leading to the conclusion that the high flowability of SCC has little effect on the flexural, shear and bond strengths of concrete members.

• 한국구조물진단유지관리공학회 논문집
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• 제21권3호
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• pp.130-137
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• 2017

본 연구에서는 기존의 저자 등에 의해 수행된 유연도법에 근거한 보-기둥 섬유요소에 수치해석적 방법으로부터 전단변형 효과를 고려할 수 있도록 수정된 정식화 방안과 단면에 대한 비탄성 전단응답 이력 구성관계식을 새로이 제안함으로써 전단 및 휨 - 전단파괴 양상을 나타내는 철근콘크리트 보에 대한 합리적인 해석적 방안을 마련하는 것을 목표로 한다. 주요 실험변수들이 전단거동 특성에 미치는 영향을 파악하기 위하여 모두 종방향 철근의 항복전에 전단파괴가 일어나도록 설계된 총 6개의 철근콘크리트 보 실험체를 검증 대상으로 저자 등에 의해 새로이 수정된 구성관계식을 적용한 비선형 유한요소해석 프로그램(RCAHEST)을 통한 해석을 수행하였다. 모든 실험체에 대한 파괴모드와 파괴시까지의 전반적인 거동 특성을 비교적 적절히 예측하고 있음을 확인하였으며 이러한 연구결과들은 향후, 대형화 복잡화 되어가고 있는 전체 구조물에 대한 신뢰도 높은 해석을 수행하기 3차원 해석에도 충분히 활용될 수 있을 것으로 기대된다.

• Structural Engineering and Mechanics
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• 제33권2호
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• pp.137-158
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• 2009

This paper investigates the behavior of reinforced concrete (RC) circular columns under combined loading including torsion. The main variables considered in this study are the ratio of torsional moment to bending moment (T/M) and the level of detailing for moderate and high seismicity (low and high transverse reinforcement/spiral ratio). This paper presents the results of tests on seven columns subjected to cyclic bending and shear, cyclic torsion, and various levels of combined cyclic bending, shear, and torsion. Columns under combined loading were tested at T/M ratios of 0.2 and 0.4. These columns were reinforced with two spiral reinforcement ratios of 0.73% and 1.32%. Similarly, the columns subjected to pure torsion were tested with two spiral reinforcement ratios of 0.73% and 1.32%. This study examined the significance of proper detailing, and spiral reinforcement ratio and its effect on the torsional resistance under combined loading. The test results demonstrate that both the flexural and torsional capacities are decreased due to the effect of combined loading. Furthermore, they show a significant change in the failure mode and deformation characteristics depending on the spiral reinforcement ratio. The increase in spiral reinforcement ratio also led to significant improvement in strength and ductility.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 춘계학술발표회 논문집(I)
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• pp.126-129
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• 2006

A bending moment $M_u$ transferred at slab-column connection is resisted at the slab critical section by flexure and shear. The ACI 318-05 Building Code(1) gives an empirical equation for the fraction ${\gamma}_{\upsilon}$ of the moment $M_u$ to be transferred by shear at the slab critical section at d/2 from the column face and also the effective wide(c+3h). The equation is based on tests of interior slab-column connections without shear reinforcement. In order to investigate the data eight test specimens were examined. The test shows that increased slab load substantially reduces both the unbalanced moment capacity and the lateral drift capacity of the connection. Especially, the specimens with the bottom reinforcement existence and nonexistence, appears remarkable differences. Studies also show that the code equation for ${\gamma}_{\upsilon}$ does not apply to all cases. The purpose of this study is to compare the test results with present ACI 318-05 Building Code provisions for design of slab-column connections and with the analysis of the experimental data for a new limitation of strength equation without shear reinforcement and bottom reinforcement.