• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1993년도 가을 학술발표회 논문집
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• pp.184-189
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• 1993

This is an experimental investigation the shear behavior of reinforced concrete with stirrup of which stress ranges 0.0㎏/㎠ to 7.0㎏/㎠. Five rectangular beams which concrete strengths are 287㎏/㎠ and 380㎏/㎠, a/d=3, and main steel ratio equal to 1.96% was tested. Those were designed to fail in shear. The shear cracking load and failure load were measured and compared with ACI's equation and Zutty's proposed equation. The results are following : ACI equation and Zutty's equation are consertive. As the concrete compressive strength increased, reserved shear strength of beams with minimum web reinforcement decreases. According to increase of web reinforcement , the rate of increases of shear strength is decreased. The failure modes of specimen with minimum web reinforcement are shear compression failure which is reached after diagonal shear cracking.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1992년도 봄 학술발표회 논문집
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• pp.86-89
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• 1992

In the precast segmental method of construction, segments of a structure are precast, assembled, and tied together by post-tensioning to form the structure. Shear strength and behavior of points in precast concrete structures are important problems in the design of these structures. An experimental program was set up study the shear behavior of precast concrete shear keys. experimental models of keyed joints include a single key, representing one of a series include the shear key shape, d/h ratio(1/4, 1/5, 1/7), and inclined angle (45。 60。 75。). Two different types of joints, i.e., epoxied joint and dry joints were studied. From the present tests, it is found that epoxied joints have higher shear strength than those of dry joints, and that high d/h ratio keys have higher shear strength than those of low d/h ratio keys. The keys with 60。-inclined angle shows the highest shear strength among various angles.

• 콘크리트학회논문집
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• 제29권3호
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• pp.259-266
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• 2017

본 연구는 PHC말뚝의 단점인 전단력을 보강한 기능성말뚝을 개발하여 보다 경제적이고 합리적인 말뚝의 현장 적용에 기여하고자 하였다. 본 연구를 통해 개발된 CFP말뚝은 링형 합성 전단연결재를 배치하고 PHC말뚝 중공부에 콘크리트를 속채움함으로써 말뚝의 전단성능을 증대시키고, PHC말뚝 내 보강철근(H13-8ea)과 말뚝 중공부의 보강철근(H19-8ea)을 배치하여 횡보강철근비 증대에 따른 전단강도를 향상시켰다. 또한, 속채움 콘크리트와 PHC말뚝의 합성거동을 위해 말뚝 보강철근의 정착 홀이 형성된 합성 전단연결재를 배치하여 보강철근의 다월력을 말뚝의 전단강도 증진에 효과적으로 반영시켰다. CFP말뚝의 전단설계와 성능을 검증하고자 도로교설계기준의 한계상태설계법(2012)을 적용한 전단강도를 산출하였고, 말뚝 시험규정인 KS F 4306에서 제시한 실험방법을 통해 결과값을 비교 검토하였다. CFP말뚝의 단면별 설계전단강도와 실험결과 각 시험체는 설계전단강도 대비 평균 2.20, 2.15, 2.05의 안전율을 확보하는 것으로 나타나 효과적인 전단강도 예측이 가능할 것으로 생각된다.

• 한국공간구조학회논문집
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• 제19권4호
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• pp.53-60
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• 2019

In this study, an experimental study was carried out to evaluate the bond shear performance according to the shear connector between the glue-laminated timber and steel interface. Ten block shear specimens were fabricated according to the configuration of the adhesive surface of wood and steel. In addition, four test specimens were produced according to the main variable shape of the wood-concrete shear connector. As a result of the block shear test, the shear strength of the steel-wood adhesive is shown to have a shear performance greater than the wood-wood shear strength. As a result of the push-out test according to the shape of the shear connector, the shear strength increased linearly with the attachment area. The complete composite behavior between the glued-laminated timber and the steel can be secured.

• 콘크리트학회논문집
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• 제22권5호
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• pp.711-718
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• 2010

콘크리트구조설계기준(2007)에서 제한하는 전단보강철근의 최대 항복강도와 ACI 318-08 기준식, EC2-02 기준식, CSA-04 기준식, JSCE-04 기준식에서 요구하는 전단보강철근의 최대 항복강도에는 많은 차이가 있다. 이 연구에서는 18개의 철근콘크리트 보 실험을 통하여 전단보강철근의 항복강도와 콘크리트의 압축강도가 부재의 전단거동에 미치는 영향을 파악하였다. 실험에 의하면 콘크리트구조설계기준(2007)에서 요구하는 전단보강철근의 최대 항복강도보다 최대 약 1.88배까지의 고강도 전단보강철근을 배근하였음에도 불구하고 실험결과는 전단보강철근이 항복한 이후에 부재가 최대 내력에 도달하였다. 또한 모든 실험체의 전단 내력은 전단보강철근의 양이 증가함에 따라서 거의 선형적으로 증가하였다. 사인장균열에 대해서는 전단보강철근의 항복강도가 증가함에 따라서 균열의 수가 증가하였고, 동일한 하중비에 대하여 보통강도 전단보강철근을 사용한 보의 사인장균열 폭과 고강도 전단보강철근을 사용한 보의 사인장균열 폭은 거의 유사하였다.

• Smart Structures and Systems
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• 제3권1호
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• pp.51-68
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• 2007

High-strength concrete (HSC) is becoming increasingly attractive for various construction projects since it offers a multitude of benefits over normal-strength concrete (NSC). Unfortunately, current design provisions for shear capacity of RC slender beams are generally based on data developed for NSC members having a compressive strength of up to 50 MPa, with limited recommendations on the use of HSC. The failure of HSC beams is noticeably different than that of NSC beams since the transition zone between the cement paste and aggregates is much denser in HSC. Thus, unlike NSC beams in which micro-cracks propagate around aggregates, providing significant aggregate interlock, micro-cracks in HSC are trans-granular, resulting in relatively smoother fracture surfaces, thereby inhibiting aggregate interlock as a shear transfer mechanism and reducing the influence of compressive strength on the ultimate shear strength of HSC beams. In this study, a new approach based on genetic algorithms (GAs) was used to predict the shear capacity of both NSC and HSC slender beams without shear reinforcement. Shear capacity predictions of the GA model were compared to calculations of four other commonly used methods: the ACI method, CSA method, Eurocode-2, and Zsutty's equation. A parametric study was conducted to evaluate the ability of the GA model to capture the effect of basic shear design parameters on the behaviour of reinforced concrete (RC) beams under shear loading. The parameters investigated include compressivestrength, amount of longitudinal reinforcement, and beam's depth. It was found that the GA model provided more accurate evaluation of shear capacity compared to that of the other common methods and better captured the influence of the significant shear design parameters. Therefore, the GA model offers an attractive user-friendly alternative to conventional shear design methods.

• 콘크리트학회논문집
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• 제21권1호
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• pp.75-84
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• 2009

이전 연구에서 제안된 변형률 기반 전단강도모델에 근거하여, 프리스트레스트 콘크리트 보의 전단강도를 예측하기 위한 해석모델을 제안하였다. 전단보강 되지 않은 콘크리트 보에서는 일반적으로 인장대보다 콘크리트 압축대가 주로 전단력에 저항한다. 콘크리트의 전단성능은 콘크리트의 재료 파괴기준을 통해 정의된다. 압축대의 전단성능은 단면에 작용하는 수직응력과의 상관관계를 고려하여, 경사 파괴면을 따라서 산정된다. 압축대의 수직응력 분포는 부재의 휨변형에 따라 변화하므로, 압축대 단면의 전단성능은 휨변형에 대한 함수이다. 보의 전단강도는 전단성능 곡선과 전단수요 곡선의 교점에서 결정된다. 제안된 해석모델을 기존 연구자들의 실험 연구 결과와 비교한 결과, 실험체의 전단강도를 정확하게 예측하였다.

• Restorative Dentistry and Endodontics
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• 제24권1호
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• pp.26-39
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• 1999

Bis-GMA, the representative monomer of bonding resin, contributes to the rigidity of bonding layer. Hydrophilic monomer contributes to the permeability into dentin substrates while weaken the bonding layer due to its small molecular weight. The degree of conversion also contributes to the ultimate strength of the bonding layer. This study was performed for the correlation analysis of monomer ratio and dentin bonding strength via degree of conversion. 7 experimental bonding resins were prepared with Bis-GMA, ratio from 20% to 80% by 10% increment, and hydrophilic HEMA monomer. Their degree of conversion and shear bond strength to dentin were compared with Scotchbond Multi-Purpose adhesive, and the fractured surfaces were examined microscopically. The results were as follows; 1. The degree of conversion increased when, the ratio of Bis-GMA increased from 20% to 70%, whereas it decreased when the ratio of Bis-GMA was 80%. 2. Shear bond strengths of the experimental bonding resins of 80%, 70%, 60% ratio of Bis-GMA were significantly higher than those of the experimental bonding resin of 50% ratio of Bis-GMA and Scotchbond Multi-Purpose adhesive. Lower shear bond strengths were obtained with the experimental bonding resins of 40%, 30%, 20% ratio of Bis-GMA (p<0.05). 3. Adhesive fractures were associated with the bonding resins of the lower bond strength, while cohesive fractures within the bonding resin layer were associated with the bonding resins of higher bond strength. Bonding resins with shear bond strength higher than 18MPa showed some cohesive fractures within the composite resin or within the dentin. 4. Correlations between Bis-GMA ratio and the degree of conversion (r=0.826), between Bis-GMA ratio and shear bond strength (r=0.853), and between the degree of conversion and shear bond strength (r=0.786) were significant (p<0.05).

• 대한치과교정학회지
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• 제22권1호
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• pp.43-65
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• 1992

Bonding orthodontic adhesive resins to glazed porcelain surface is not attainable. The aim of this investigation was to examine, in vitro, the effect of three methods of porcelain surface pretreatment on the shear bond strength of orthodontic adhesives, and to compare the shear strength of orthodontic bracket bonding to porcelain surface by the best results that to human enamel. Porcelain disks ($Ceramco^{(TM)}$ and $Vita^{(TM)}$) baked in the laboratory were roughened by sandpapers, #320, #600, #800, #1000 and #1200, and were pretreated with silane and dried at the various temperatures, room temperature, $50^{\circ}C$, $70^{\circ}C$ and $90^{\circ}C$, and were etched by 3% hydrofluoric acid solution for 1, 3, 5, 7, and 9 minutes, orthodontic adhesives (System $1+^{(TM)}$ and $Unite^{(TM)}$) were applied on them, and shear bond strengths were measured by Instron. The best results of pretreatment of each method were determined by the shear bond strengths. Again, porcelain disks were pretreated by the determined best results and human enamel were etched by 37% hydrofluoric acid solution, orthodontic brackets were bonded on them by the orthodontic adhesives, and the shear bond strengths were measured and compared between them. 1. Roughening porcelain surfaces with coarse sandpaper (#300) showed higher shear bond strength than that with finer sandpapers, but it $(22.44Kgf/cm^2)$ was distinguishably low compared to that from etched human enamel $(144.11Kgf/cm^2)$. 2. There were disparities in shear bond strengths upon the orthodontic resins, which was presumably related to the contents of fillers in orthodontic adhesive resins. Also there were disparities in shear bond strength upon the porcelains which had different composition. 3. Silane enhanced the shear bond strength of orthodontic resins to porcelain surfaces ($25.20Kgf/cm^2$ at $50^{\circ}C$), which was markedly low compared to that from etched human enamel. 4. Etched porcelain surface with 3% hydrofluoric acid solution for 1 to 9 minutes showed no difference in shear bonding strength of orthodontic adhesive resins. Shear bond strength from etched porcelain $(97.43-120.72Kgf/cm^2)$ were as high as clinically available, but low compared to that from etched human enamel. 5. Roughening with #300 sandpaper and etching by 3% hydrofluoric acid followed silane application on porcelain surface showed lower shear bond strength than etched human enamel, but were as high as clinically useful. 6. The results suggest that etching porcelain surface by 3% hydrofluoric acid solution might provide comparatively high shear bond strength as much as clinically favorable.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2000년도 가을 학술발표회 논문집
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• pp.3-14
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• 2000

Anisotropic consolidation, shear, a transportational component during or after deposition each may produce anisotropic fabrics, which result in the anisotropic properties of soils. Nevertheless, the isotropically consolidated compression triaxial tests are commonly used in practice to determine the strength of the anisotropically consolidated soils because of their practicality and simplicity. In this paper the effects of anisotropic consolidation on the strength properties of soils are discussed. For the sandy soils consolidated under a constant vertical consolidation pressure, the deformation modulus decreases with decreasing consolidation pressure ratio($\sigma$$\sub$3c/'/$\sigma$ sub 1c/'), but the liquefaction resistance increases. For the saturated cohesive soils, both the undrained shear strength and undrained creep strength decrese with decreasing the consolidation pressure ratio. When the in-situ strength properties of the anisotropically and normally consolidated soils are determined by the isotropically consolidated tests, the undrained shear strength and creep strength of saturated cohesive soils as well as the deformation modulus of sandy soils are measured to be higher than the rear in-situ values. This, therefore, could lead to a dangerous judgement in stability analysis