• 한국농공학회지
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• 제38권3호
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• pp.58-69
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• 1996

In recent years, the research and development about the new material proceeds rapidly and actively. In building industry, high strength concrete is of interest as a new material. Since the building structure becomes bigger, higher and more specialized, the demand of material and member with high strength expands greatly. Therefore in this experiment, cement complex with high strength was made using the condensed silica fume, a basic experiment was performed on strength property, and optimum-mixture-state was determined for manufacturing a high-strength concrete. Shear behaviour and fracture property of concrete beams with high strength were evaluated. On the whole, in spite of many researches, it is one of the difficult problems that shear fracture of concrete beams has not yet been clearly understood theoretically, and now the shear-design-standard forms in many countries are a formula based on experiment. In this study, the variable of shear behavior experiment was shear-reinforcement-ratio. By analyzing test results and comparing with computation value by ACI code, the basic data was offered on shear design of reinforced concrete beams with high strength. The effect of epoxy repair was also investigated for the beams with cracks due to flexural and shear loading.

• Steel and Composite Structures
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• 제17권6호
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• pp.967-980
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• 2014

In regions of high shear forces in composite bridges, headed stud shear connectors need to be arranged with a small spacing in order to satisfy the design requirement of resisting the high interface shear force present at this location. Despite this, studies related to groups of headed studs are somewhat rare. This paper presents an investigation of the static behaviour of grouped stud shear connectors in high-strength concrete. Descriptions are given of five push-out test specimens with different arrangements of the studs that were fabricated and tested, and the failure modes, load-slip response, ultimate load capacities and related slip values that were obtained are reported. It is found that the load-slip equation given by some researchers based on a single stud shear connector in normal strength concrete do not apply to grouped stud shear connectors in high-strength concrete, and an algebraic load-slip expression is proposed based on the test results. Comparisons between the test results and the formulae provided by some national codes show that the equations for the ultimate capacity provided in these codes are conservative when used for connectors in high-strength concrete. A reduction coefficient is proposed to take into account the effect of the studs being in a group.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 추계 학술발표회 논문집
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• pp.201-204
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• 2006

The shear resistance of RC beams is subject to the amount of shear-reinforcing bars ($p_w$) and yield strength ($f_{wy}$) as well as their interactive influence ($p_wf_{wy}$). Thus, it is reasonably expected that high-strength steel bars can greatly reduce the necessary amount of shear-reinforcing bars. On the other hand, although the bond strength is influenced by the amount of shear reinforcing bars, it is not affected by the yield strength. Thus, there is often an issue that bond failure occurs before shear failure depending on the arrangement of shear reinforcing bars. It is a common practice to set sub-ties for the transverse confinement of the main re-bars as a method to prevent the bond failure. However, it can also become a factor in decreased work efficiency due to the complexity of the construction. This study experimented with simultaneous use of high-strength transverse reinforcing bars ($f_{wy}=800MPa$) and U-shaped transverse reinforcing bars of regular strength ($f_{wy}=300MPa$) in an attempt to decrease the necessary quantity of shear reinforcing bars. The effect of this attempt was investigated through fundamental experimental research in terms of the improvement in shear resistance and bond strength as well as the ease of construction.

• Computers and Concrete
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• 제17권6호
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• pp.723-737
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• 2016

In this paper an approach was described for determination of direction of sliding block in rock slopes containing planar non-persistent open joints. For this study, several gypsum blocks containing planar non-persistent open joints with dimensions of $15{\times}15{\times}15cm$ were build. The rock bridges occupy 45, 90 and $135cm^2$ of total shear surface ($225cm^2$), and their configuration in shear plane were different. From each model, two similar blocks were prepared and were subjected to shearing under normal stresses of 3.33 and $7.77kg/cm^{-2}$. Based on the change in the configuration of rock-bridges, a factor called the Effective Joint Coefficient (EJC) was formulated, that is the ratio of the effective joint surface that is in front of the rock-bridge and the total shear surface. In general, the failure pattern is influenced by the EJC while shear strength is closely related to the failure pattern. It is observed that the propagation of wing tensile cracks or shear cracks depends on the EJC and the coalescence of wing cracks or shear cracks dominates the eventual failure pattern and determines the peak shear load of the rock specimens. So the EJC is a key factor to determine the sliding direction in rock slopes containing planar non-persistent open joints.

• 국제강구조저널
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• 제18권4호
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• pp.1297-1305
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• 2018

The corrugated steel plate shear walls have recently been proposed to address the seismic issues associated with simple steel plate shear walls; however, stiffness, strength, and ductility of the corrugated shear walls are significantly affected by varying the corrugation geometry under seismic loading. The present study investigates steel shear walls' models with corrugated or simple infill plates subjected to monotonic and cyclic loads. The performance of the corrugated steel plate is evaluated and then compared to that of the simple steel plates by evaluating the damping ratios and energy dissipation capability. The effect of corrugation profile angle, the existence of an opening, and the corrugation subpanel length are numerically investigated after validation of the finite element modeling methodology. The results demonstrate that incorporating corrugated plates would lead to better seismic damping ratios, specifically in the case of opening existence inside of the infill plate. Specifically, the corrugation angle of $30^{\circ}$ decreases the ultimate strength, while increasing the initial stiffness and ductility. In addition, the subpanel length of 100 mm is found to be able to improve the overall performance of shear wall by providing each subpanel appropriate support for the adjacent subpanel, leading to a sufficient buckling resistance performance.

• Geomechanics and Engineering
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• 제23권6호
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• pp.587-600
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• 2020

Shear-induced instability of jointed rock mass has greatly threatened the safety of underground openings. To better understand the failure mechanism of surrounding rock mass under shear, the flawed specimens containing a circular opening and two open joints are prepared and used to conduct direct shear tests. Both experimental and numerical results show that joint inclination (β) has a significant effect on the shear strength, dilation, cracking behavior and stress distribution around flaws. The maximum shear strength, occurring at β=30°, usually corresponds to a unifrom stress state around joint and an intense energy release. However, a larger joint inclination, such as β=90°~150°, will cause a more uneven stress distribution and a stronger stress concentration, thus a lower shear strength. The stress distribution around opening changes little with joint inclination, while the magnitude varys much. Both compression and tension around opening will be greatly enhanced by the 30°-joints. In addition, a higher normal stress tends to enhance the compression and suppress the tension around flaws, resulting in an earlier generation and a larger proportion of shear cracks.

• Composites Research
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• 제19권5호
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• pp.1-6
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• 2006

본 연구에서는 폐쇄형 단면을 갖는 박판 복합재료 보의 정밀 i차원 보 해석모델을 개발하였다. 혼합보 이론을 이용하여 복합재료 보에 대한 전단 흐름 분포 및 단면 강성 행렬에 대한 엄밀해 표현식을 유도하였다. 이를 단일 세포 상자형 단면을 갖는 복합재료 보에 적용하여 상자형 보의 단면 강성행렬에 대한 엄밀해 표현식을 얻었다. 상자형 복합재료 보의 전단 중심을 계산하였으며, 전단 변형 효과가 폐쇄형 단면 보의 정적 거동에 미치는 영향에 대해서 고찰하였다. MSC/Nastran을 이용한 유한요소 해석을 통하여 본 연구의 타당성을 도였다.

• Computers and Concrete
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• 제31권2호
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• pp.123-137
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• 2023

To fully understand shear mechanisms and composite effects of circular concrete-filled steel tube (CFST) columns, systematic numerical investigations were conducted in this paper by improved finite element models. The triaxial plastic-damage constitutive model of the concrete and the interactions between the concrete and steel tube were considered. Afterwards, the critical and upper bound shear span ratios of the circular CFST column under lateral shear loading were determined. The composite effects between the two materials were analyzed by comparing the shear resistance with plain concrete column and hollow steel tube. In addition, a method that predicts the shear bearing capacity of a circular CFST column was proposed. The confining effects on the concrete core and the restraining effects on the steel tube were considered in this method. The proposed formula can predict more accurate results than the methods in different codes and references.

• Earthquakes and Structures
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• 제26권6호
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• pp.449-461
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• 2024

The vertical reinforcement connection between the precast reinforced concrete shear wall and the cast-in-place reinforced concrete member is vital to the performance of shear walls under seismic loading. This paper investigated the structural behavior of three precast reinforced concrete shear walls, with different levels of connection (i.e., full connection, partial connection, and no connection), subjected to quasi-static lateral loading. The specimens were subjected to a constant vertical load, resulting in an axial load ratio of 0.4. The crack pattern, failure modes, load-displacement relationships, ductility, and energy dissipation characteristics are presented and discussed. The resultant seismic performances of the three tested specimens were compared in terms of skeleton curve, load-bearing capacity, stiffness, ductility, energy dissipation capacity, and viscous damping. The seismic performance of the partially connected shear wall was found to be comparable to that of the fully connected shear wall, exhibiting 1.7% and 3.5% higher yield and peak load capacities, 9.2% higher deformability, and similar variation in stiffness, energy dissipation capacity and viscous damping at increasing load levels. In comparison, the seismic performance of the non-connected shear wall was inferior, exhibiting 12.8% and 16.4% lower loads at the yield and peak load stages, 3.6% lower deformability, and significantly lower energy dissipation capacity at lower displacement and lower viscous damping.

• 콘크리트학회논문집
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• 제26권4호
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• pp.533-543
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• 2014

최근 들어, 지하주차장과 같은 모듈화 건물에 프리캐스트 콘크리트와 현장타설 콘크리트가 함께 사용되는 복합공법의 사용이 증가하고 있다. 일반적으로 프리캐스트 콘크리트는 공장에서 선 제작되기 때문에 재료의 효율성을 극대화하기 위해 프리텐션을 도입하여 사용한다. 현행 구조기준이 긴장력이 가해진 단일 단면의 전단 강도식은 제시하지만 긴장력이 가해진 프리캐스트와 현장타설 콘크리트 합성단면의 전단강도식은 제시하지 못하고 있는 실정이다. 따라서 긴장력이 가해진 합성 부재의 전단강도 실험을 통해 긴장력이 전단강도에 미치는 영향과 합성부재의 전단강도 산정시 고려해야할 사항에 대해 알아보았다. 변수로는 콘크리트의 면적비, 긴장재의 긴장력, 전단 경간비, 그리고 전단철근비를 고려하였다. 실험 결과를 분석해보면, 전단강도는 긴장력 크기와 긴장력이 가해진 단면의 면적비가 커질수록 증가하였고 전단경간비가 증가할수록 감소하였다.