• 한국해양공학회지
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• 제21권6호
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• pp.7-15
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• 2007

A mechanical model was developed to predict the behavior of point-loaded RC slender beams (a/d > 2.5) without stirrups. It is commonly accepted by most researchers that a diagonal tension crack plays a predominant role in the failure mode of these beams, but the failure mechanism of these members is still debatable. In this paper, it was assumed that diagonal tension failure was triggered by the concrete cover splitting due to the dowel action at the initial location of diagonal tension cracks, which propagate from flexural cracks. When concrete cover splitting occurred, the shape of a diagonal tension crack was simultaneously developed, which can be determined from the principal tensile stress trajectory. This fictitious crack rotates onto the crack tip with load increase. During the rotation, all forces acting on the crack (i.e, dowel force of longitudinal bars, vertical component of concrete tensile force, shear force by aggregate interlock, shear force in compression zone) were calculated by considering the kinematical conditions such as crack width or sliding. These forces except for the shear force in the compression zone were uncoupled with respect to crack width and sliding by the proposed constitutive relations for friction along the crack. Uncoupling the shear forces along the crack was aimed at distinguishing each force from the total shear force and clarifying the failure mechanism of RC slender beams without stirrups. In addition, a proposed method deriving the dowel force of longitudinal bars made it possible to predict the secondary shear failure. The proposed model can be used to predict not only the entire behavior of point-loaded RC slender shear beams, but also the ultimate shear strength. The experiments used to validate the proposed model are reported in a companion paper.

• 한국구조물진단유지관리공학회 논문집
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• 제3권3호
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• pp.139-147
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• 1999

Six reinforced concrete shear wall, constructured with fully rigid, slit, and infilled types, were tested under both vertical and cyclic loadings. Experimental programs were carried out to evaluate the seismic performance of such test specimens, such as the hysteretic behavior, the maximum horizontal strength, crack propagation, and ductility, under load reversals. All the specimens were modeled in one-third scale size. Based on the test results, the following conclusions can be made. For the diagonal reinforced slit and infilled shear wall specimens, it was found that the failure mode shows very effective crack control and crushing due to slippage prevention of boundary region and reduction of diagonal tension rathar than the brittle shear and diagonal tension failure. The ductility of specimens designed by the diagonal reinforcement for the slit and infilled shear wall was increased 1.72~1.81 times in comparison with the fully rigid shear wall frame. Maximum horizontal load-carrying capacity of specimens designed by the diagonal reinforcement ratio the slit and infilled shear wall was increased respectively by l.14 times and l.49 times in comparison with the standard fully rigid shear wall frame.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 봄 학술발표회 논문집(I)
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• pp.683-688
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• 1999

The purpose of this study is to develop and evaluate the structural performance of various shear walls, such as the hysteretic behavior, the maximum horizontal strength, crack propagation, and ductility etc. under load reversals. For the diagonal reinforced slit and infilled shear wall specimens, it was found that the failure mode shows very effective crack control and crashing due to slippage prevention of boundary region and reduction of diagonal tension rather than the brittle shear and diagonal tension failure. The ductility of specimens designed by the diagonal reinforcement for the slit and infilled shear wall was increased 1.72~1.81 times in comparison with the fully rigid shear wall frame. Maximum horizontal load-carrying capacity of specimens designed by the diagonal reinforcement ratio the slit and infilled shear wall was increased respectively by 1.14 times and 1.49 times in comparison with the standard fully rigid shear wall frame.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2000년도 춘계 학술발표회 논문집 Proceedings of EESK Conference-Spring
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• pp.178-185
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• 2000

A set of tests were accomplished in order to get better insight of the basic material properties of masonry made of normal concrete brick and different type of mortar compositions. Three different types of test were performed. Masonry unit and prism were tested by compressive strength test, Masonry wallets were tested by compressive strength test. Masonry wallets were tested in diagonally under tension. A significant influence of different mortar compositions on compression strength of masonry prism was observed, The tests have shown that for diagonal compression three different mode of failure were possible : tension crack along the loaded diagonal sliding along a mortar joint and combined sliding and diagonal crack according to the adhesive strength of a mortar.

• 콘크리트학회지
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• 제4권4호
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• pp.171-179
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• 1992

본 연구에서는 전단-스팬비가 1.5에서 2.5 범위의 고강도 콘크리트 보에 대해 기존 규준식의 안전여부를 확인하고, 사균열강도와 극한전단강도를 결정하기 위해 총 15개의 시험체를 제작하여 실험적 연구를 수행하였다. 주요변수는 전단-스팬비(a/d=1.5, 2.0, 2,5)와 수직전단철근비(Rv=0, 25, 50, 75, 100%, Rv=[$ ho$v / $\rho$v(ACI)] 100)이며, 콘크리트 압축강도(f＇c=747kg/$ extrm{cm}^2$와 인장철근비($\rho$w=0.0377)는 일정하다. 실험결과 본 연구의 전단-스팬비의 범위에서 ACI 318-89 (11-31)식은 일반적으로 수직전단철근에 의해 저항되는 전단강도를 상당히 과소평가하는 것으로 나타났다. 따라서 수직전단철근에 대한 영향이 재고되어야 할 것이다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 봄학술 발표회 논문집(II)
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• pp.321-324
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• 2005

This paper presents a preliminary study on the influence of material ductility on diagonal tension behavior of shear-wall panels. There have been a number of previous studies, which suggest that the use of high ductile material such as ECC (Engineered Cementitious Composite) significantly enhanced shear capacity of structural elements even without shear reinforcements involved. The present study emphasizes increased shear capacity of shear-wall panels by employing a unique strain-hardening ECC reinforced with poly(vinyl alcohol) (PVA) short random fibers. Normal concrete was adopted as the reference material. Experimental investigation was performed to assess the failure mode of shear-wall panels subjected to knife-edge loading. The results from experiments show that ECC panels exhibit a more ductile failure mode and higher shear capacity when compared to ordinary concrete panels. The superior ductility of ECC was clearly reflected by micro-crack development, suppressing the localized drastic fracture typically observed in concrete specimen. This enhanced structural performance indicates that the application of ECC for a in-filled frame panel can be effective in enhancing seismic resistance of an existing frame in service.

• Computers and Concrete
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• 제20권6호
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• pp.689-704
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• 2017

The paper presents experimental and numerical investigations of prefabricated composite structural building reinforced concrete slabs with the insulating material for a residential building construction. The building slabs were composed of concrete and expanded polystyrene. In experiments, the slabs in the full-scale 1:1 were subjected to vertical concentrated loads and failed along a diagonal shear crack. The experiments were numerically evaluated using the finite element method based on two different constitutive continuum models for concrete. First, an elasto-plastic model with the Drucker-Prager criterion defined in compression and with the Rankine criterion defined in tension was used. Second, a coupled elasto-plastic-damage formulation based on the strain equivalence hypothesis was used. In order to describe strain localization in concrete, both models were enhanced in the softening regime by a characteristic length of micro-structure by means of a non-local theory. Attention was paid to the formation of critical diagonal shear crack which was a failure precursor.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 춘계 학술발표회 제20권1호
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• pp.89-92
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• 2008

본 연구는 조적조로 구성된 치장벽체의 전단거동에 관한 연구이다. 치장조적벽체의 내진보강상 세를 소개하였으며, 본 연구에서 개발한 내진상세를 적용하여 전단거동을 평가하였다. 실험체는 비보 강조적벽(URM) 1개 보강조적벽(RM) 3개로 구성하였으며, 준정적 실험을 수행하였다. 비보강 조적벽은 형상비와 축방향 압축력에 따라 다양한 거동 및 파괴가 일어난다. 그러나 본 연구는 조적구조와는 다른 치장조적조를 대상으로 하였으므로, 전단강도의 주요변수로 작용하는 축방향 압축력은 변수에서 제외 되었다. 실험변수로는 벽체의 보강유무와 형상비로 정하였다. 실험결과 실험체의 거동은 강체회전(Rocking)모드가 지배적으로 나타났으나, 최종파괴는 여러 파괴모드가 복합적으로 나타났다. FEMA273 에서는 면내조적벽의 전단강도식을 제시한다. 강도식은 조적벽의 거동모드에 따라 4가지로 분류되며, 그 거동모드는 강체회전(Rocking), 단부압괴(Toe-Crushing), 수평줄눈미끄러짐(Bed-Joint-Sliding), 사인장(Diagonal-Tension)파괴로 나타내고 있다. FEMA 273에 의해 전단강도를 평가한 결과 치장조적벽의 거동모드는 어느정도 예측 할 수 있었지만, 전단강도는 매우 다르게 나타났다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1995년도 가을 학술발표회 논문집
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• pp.187-192
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• 1995

Four types of experiments were performed to check the similitude of member behavior between prototype and 1/10 scale models:(1) Test of slender columns with P- effect, (2)Test of short columns with and without confinement steel, (3)Test of simple beams without stirrups, and (4)T-beam test. Based on the results of experiments, the conclusions were made as follows : (1) The P- effect of slender columns can be almost exactly represented by 1/10 acale model. (2)The effect of confinement on short columns by the hoop steel can also roughly simulated by 1/10 scale model. (3)The failure modes of simple beams models were the yielding of tension steel followed by large diagonal tension cracking+compressive concrete failure. (4)The behaviors of prototype and 1/10 scale model in T-beams appear very similar.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 춘계학술발표회 논문집(I)
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• pp.46-49
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• 2006

In general, the shear behavior mode of URM wall expresses four types of modes such as rocking failure, sliding shear failure, toe crushing failure, and diagonal tension failure. From the comparison of each equation according to the shear behavior modes, the failure modes based on the aspect ratio and vertical axial stress can be expected. The objectives of this study is to find out the shear behavior of URM wall with different aspect ratio. The test results show that the aspect ratio is understood as an important variable.