• Geomechanics and Engineering
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• 제16권4호
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• pp.385-397
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• 2018

This study evaluates the interfacial properties of composite specimens consisting of shotcrete and sprayed waterproofing membrane. Two different membrane prototypes were first produced and tested for their waterproofing ability. Then composite specimens were prepared and their interfacial properties assessed in direct shear and uniaxial compression tests. The direct shear test showed the peak shear strength and shear stiffness of the composites' interface decreased as the membrane layer became thicker. The shear stiffness, a key input parameter for numerical analysis, was estimated to be 0.32-1.74 GPa/m. Shear stress transfer at the interface between the shotcrete and membrane clearly emerged when measuring peak shear strengths (1-3 MPa) under given normal stress conditions of 0.3-1.5 MPa. The failure mechanism was predominantly shear failure at the interface in most composite specimens, and shear failure in the membranes. The uniaxial compression test yielded normal stiffness values for the composite specimens of 5-24 GPa/m. The composite specimens appeared to fail by the compressive force forming transverse tension cracks, mainly around the shotcrete surface perpendicular to the membrane layer. Even though the composite specimens had strength and stiffness values sufficient for shear stress transfer at the interfaces of the two shotcrete layers and the membrane, the sprayed waterproofing membrane should be as thin as possible whilst ensuring waterproofing so as to obtain higher strength and stiffness at the interface.

• Steel and Composite Structures
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• 제42권2호
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• pp.265-275
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• 2022

A new type of precast steel reinforced concrete (PSRC) column was put forward in this paper. In order to study the static performance of PSRC column and hollow precast steel reinforced concrete (HPSRC) column subjected to combined compression and shear loading, a parametric test was carried out and effects of axial compression ratio, concrete strength and shear ratio on the mechanical behavior of composite PSRC column and HPSRC column were explored. In addition, the cracks development, load-span displacement relationship, strain distribution and shear bearing strength of column specimens were emphatically focused. Test results implied that shear failure of all specimens occurred during the test, and higher strength of cast-in-place concrete, smaller shear ratio and larger axial compression ratio could lead to greater shear resistance, but when the axial compression ratio was larger than 0.36, the shear capacity began to decrease gradually. Furthermore, truss-arch model for determining the shear strength of PSRC column and HPSRC column was proposed and the calculated results obtained from proposed method were verified to be valid.

• Structural Engineering and Mechanics
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• 제85권4호
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• pp.563-571
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• 2023

Girdling underpinning joints are key areas of concern for the pier-cutting bridge-lifting process. In this study, five specimens of an underpinning joint were prepared by varying the cross-sectional shape of the respective column, the process used to treat the beam-column interface (BCI), and the casting process. These specimens were subsequently analyzed through static failure tests. The BCI was found to be the weakest area of the joint, and the specimens containing a BCI underwent punching shear failure. The top of the girdling beam (GB) was subjected to a circumferential tensile force during slippage failure. Compared to the specimens with a smooth BCI, the specimens subjected to chiseling exhibited more pronounced circumferential compression at the BCI, which in turn considerably increased the shear capacity of the BCI and the ductility of the structure. The GB for the specimens containing a column with a circular cross-section exhibited better shear mechanical properties than the GB of other specimens. The BCI in specimens containing a column with a circular cross-section was more ductile during failure than that in specimens containing a column with a square cross-section.

• Steel and Composite Structures
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• 제20권1호
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• pp.185-203
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• 2016

Shear connectors are key components to ensure the efficient composite action and satisfactory transfer of shear forces at the steel-concrete interface in composite beams. Under hazardous circumstances, such as fire in a building, the performance of a composite beam significantly relies on the performance of shear connectors. Studies on the behavior of shear connectors subjected to elevated temperatures performed in the last decade are reviewed in this paper. The experimental testing of push-out specimens, the design approaches provided by researchers and different codes, the major failure modes, and the finite element modeling of shear connectors are highlighted. The critical research review showed that the strength of a shear connector decreases proportionally with the increase in temperature. Compared with the volume of work published on shear connectors at ambient temperatures, a few studies on the behavior of shear connectors under fire have been conducted. Several areas where additional research is needed are also identified in this paper.

• Structural Engineering and Mechanics
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• 제69권2호
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• pp.221-230
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• 2019

In this paper, shear behavior of non-persistent joint surrounded in concrete and gypsum layers has been investigated using experimental test and numerical simulation. Two types of mixture were prepared for this study. The first type consists of water and gypsum that were mixed with a ratio of water/gypsum of 0.6. The second type of mixture, water, sand and cement were mixed with a ratio of 27%, 33% and 40% by weight. Shear behavior of a non-persistent joint embedded in these specimens is studied. Physical models consisting of two edge concrete layers with dimensions of 160 mm by 130 mm by 60 mm and one internal gypsum layer with the dimension of 16 mm by 13 mm by 6 mm were made. Two horizontal edge joints were embedded in concrete beams and one angled joint was created in gypsum layer. Several analyses with joints with angles of $0^{\circ}$, $30^{\circ}$, and $60^{\circ}$ degree were conducted. The central fault places in 3 different positions. Along the edge joints, 1.5 cm vertically far from the edge joint face and 3 cm vertically far from the edge joint face. All samples were tested in compression using a universal loading machine and the shear load was induced because of the specimen geometry. Concurrent with the experiments, the extended finite element method (XFEM) was employed to analyze the fracture processes occurring in a non-persistent joint embedded in concrete and gypsum layers using Abaqus, a finite element software platform. The failure pattern of non-persistent cracks (faults) was found to be affected mostly by the central crack and its configuration and the shear strength was found to be related to the failure pattern. Comparison between experimental and corresponding numerical results showed a great agreement. XFEM was found as a capable tool for investigating the fracturing mechanism of rock specimens with non-persistent joint.

• Earthquakes and Structures
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• 제7권5호
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• pp.753-777
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• 2014

This study investigates the behavior of precast concrete cantilever wall systems with new vertical connections under cyclic loading. C-type steel connections for PC wall systems are proposed for the transfer of bending moments between walls in the vertical direction, whereas a shear key in the center of the wall is prepared to transfer shear forces by bearing pressure. The proposed connections are assembled easily because the directions of the slots are different at the edges of the walls. Structural performance characteristics such as the strength, ductility, and failure modes of test specimens were investigated. The longitudinal reinforcing steel bars, which are connected to the C-type connections, yielded first. Ultimate deformation was terminated owing to premature failure of the connections. The strength and deformation obtained from the cross-sectional analysis were generally similar to experimental data.

• Geomechanics and Engineering
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• 제33권5호
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• pp.477-486
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• 2023

In the studies on fault dislocation of tunnel, existing literatures are mainly focused on the problems caused by normal and reverse faults, but few on strike-slip faults. The paper aims to research the deformation and failure mechanism of a tunnel under strike-slip faulting based on a model test and test-calibrated numerical simulation. A potential faulting hazard condition is considered for a real water tunnel in central Yunnan, China. Based on the faulting hazard to tunnel, laboratory model tests were conducted with a test apparatus that specially designed for strike-slip faults. Then, to verify the results obtained from the model test, a finite element model was built. By comparison, the numerical results agree with tested ones well. The results indicated that most of the shear deformation and damage would appear within fault fracture zone. The tunnel exhibited a horizontal S-shaped deformation profile under strike-slip faulting. The side walls of the tunnel mainly experience tension and compression strain state, while the roof and floor of the tunnel would be in a shear state. Circular cracks on tunnel near fault fracture zone were more significant owing to shear effects of strike-slip faulting, while the longitudinal cracks occurred at the hanging wall.

• 한국구조물진단유지관리공학회 논문집
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• 제16권5호
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• pp.68-77
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• 2012

기존의 격자형 강합성 바닥판 이음부 상세는 후크형태의 철근 겹침이음 및 채움 콘크리트로 구성된다. 본 연구에서는 콘크리트 전단키와 고장력볼트로 구성된 이음부 형식에 대해 콘크리트 전단키 보강 유무를 실험변수로 휨성능평가 실험을 하였고, 그 결과를 기존 철근겹침 이음부의 휨성능과 비교 평가함으로써 기계적 연결방법에 의한 이음부 형식의 적용 가능성을 검토하였다. 실험결과의 비교 분석에 의하면, 기계적 연결방식에 의한 이음부의 최대내력이 약 30% ~ 60% 정도 더 큰 것으로 나타나서 강도 측면에서 더 우수함을 확인하였다. 모멘트-곡률 관계로부터 구한 휨강성을 비교해 보면, 철근겹침 이음부의 경우 초기 거동에서는 비교적 더 우수한 거동을 보였으나, 콘크리트 균열파괴가 발생한 이후에는 다소 급격한 단면성능의 감소를 보였다. 한편, 콘크리트 전단키의 강판 보강 유무에 따른 변수 분석 결과에 의하면 강판 보강구조가 최대내력 향상 및 휨강성 증가에 효과적임을 확인할 수 있었다.

• Geomechanics and Engineering
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• 제30권5호
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• pp.401-411
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• 2022

To obtain the dynamic mechanical properties, fracture modes, energy and brittleness characteristics of Furong Baijiao coal rock, the dynamic impact compression tests under 0, 4, 8 and 12 MPa confining pressure were carried out using the split Hopkinson pressure bar. The results show that failure mode of coal rock in uniaxial state is axial splitting failure, while it is mainly compression-shear failure with tensile failure in triaxial state. With strain rate and confining pressure increasing, compressive strength and peak strain increase, average fragmentation increases and fractal dimension decreases. Based on energy dissipation theory, the dissipated energy density of coal rock increases gradually with growing confining pressure, but it has little correlation with strain rate. Considering progressive destruction process of coal rock, damage variable was defined as the ratio of dissipated energy density to total absorbed energy density. The maximum damage rate was obtained by deriving damage variable to reflect its maximum failure severity, then a brittleness index BD was established based on the maximum damage rate. BD value declined gradually as confining pressure and strain rate increase, indicating the decrease of brittleness and destruction degree. When confining pressure rises to 12 MPa, brittleness index and average fragmentation gradually stabilize, which shows confining pressure growing cannot cause continuous damage. Finally, integrating dynamic deformation and destruction process of coal rock and according to its final failure characteristics under different confining pressures, BD value is used to classify the brittleness into four grades.

• 한국구조물진단유지관리공학회 논문집
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• 제20권1호
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• pp.41-47
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• 2016

본 연구에서는 콘크리트에 표면매입된 FRP판의 부착거동에서, 전단키와 연단거리의 효과를 관찰하기 위한 부착시험을 실시하였다. 실험에서의 주요변수는 전단키의 위치, 형태 그리고 연단길이이다. 규격 $3.6mm{\times}16mm$의 FRP를 $400mm{\times}200(300)mm{\times}400mm$ 규격의 콘크리트 블록에 매입하고 에폭시로 고정시켜서 실험변수에 따라 총 10개의 부착실험체를 제작하였다. FRP의 연단에 인장력을 가한 뒤 파괴시까지 실험을 실시하고 하중을 기록하였으며, 미끄러짐과 FRP의 인장변형량을 기록하였다. 실험으로부터, 전단키의 위치는 가력부에서 멀리 떨어질수록 전단강도가 상승하는 것으로 나타났으며, 전단키의 직경이 커질수록 내력이 저하되는 것으로 나타났다. 특히 전단키가 일정 이상의 규격이 되면 전단키가 없는 경우에 비하여 내력이 저하되어 오히려 부착강도에 부정적인 영향을 미칠 수 있는 것으로 나타났다. NSM FRP에서 응력장용방향의 연단거리가 길어짐에 따라 동일 부착길이임에도 불구하고 내력이 일부 증가하는 것으로 나타났다. 표면매입 보강된 FRP의 부착실험에서, FRP와 콘크리트사이의 부착-미끄러짐은 전체거동을 지배하는 것으로 나타나므로 이에 따른 과도한 미끄러짐은 설계에 반드시 고려될 필요가 있다.