• Journal of the Computational Structural Engineering Institute of Korea
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• v.34 no.6
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• pp.393-401
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• 2021

In this paper, we proposed a numerical model based on moment-curvature, to evaluate the resistance of reinforced concrete (RC) members subjected to blast loading. To consider the direct shear failure mode, we introduced a dimensionless spring element based on the empirical direct shear stress-slip relation. Based on the dynamic increase factor equations for materials, new dynamic increase factor equations were constructed in terms of the curvature rate for the section which could be directly applied to the moment-curvature relation. Additionally, equivalent bending stiffness was introduced in the plastic hinge region to consider the effect of bond-slip. To verify the validity of the proposed model, a comparative study was conducted against the experimental results, and the superiority of this numerical model was confirmed through comparison with the analytical results of the single-degree of freedom model. Pressure-impulse (P-I) diagrams were produced to evaluate the resistance of members against bending failure and direct shear failure, and additional parametric studies were conducted.

• Journal of the Korean Geotechnical Society
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• v.17 no.4
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• pp.279-288
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• 2001

암반내에 존재하는 불연속면은 지하구조물의 안정성에 큰 영향을 미친다. 불연속면을 해석하기 위한 구성법칙에 대한 많은 연구가 진행되어 왔으나, 객관적인 거칠기 파라미터를 이용한 전단거동 모사에 관한 연구는 아직 미흡한 실정이다. 본 연구에서는 정량적인 거칠기 파라미터를 이용한 두 가지의 새로운 구성방정식을 만들어 절리 거동을 모사하였다. 첫 번째 구성법칙은 탄소성 이론에 근거하여 두께가 없는 개별절리요소 이용한 방법이고, 두 번째 구성법칙은 3차원 레이저 변위 측정 데이터를 직접 이용하여 Ohnishi가 제안한 거칠기 손상모델을 도입하였다. 제안된 두 모델을 가지고 직접 전단시험을 모사해본 결과 실제 실험에 나타나는 변형률 경화 및 연화현상 그리고 잔류전단강도와 같은 현상을 볼 수 있었다.

• Journal of the Korea Concrete Institute
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• v.27 no.3
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• pp.299-309
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• 2015

Ultra High Performance Fiber Reinforced Concrete (UHPFRC) is distinguished from the normal concrete by outstanding compressive and tensile strength. Cracked normal concrete resists shear by aggregate interlocking while clamped by transverse reinforcement, which is called as shear friction theory. Cracked UHPFRC is expected to have a different shear transfer mechanism due to rather smooth crack face and post-cracking behavior under tensile force. Twenty-four push-off specimens with transverse reinforcement are tested for four different fiber volume ratio and three different ratio of reinforcement along the shear plane. The shear friction strength for monolithic concrete are suggested by limit analysis of plasticity and verified by test results. Plastic analysis gives a conservative, but reasonable estimate. The suggested shear friction factor and effectiveness factor of UHPFRC can be applied for interface shear transfer design of high-strength concrete and fiber reinforced concrete with post-cracking tensile strength.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.3A
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• pp.375-381
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• 2008

This paper deals with the shear capacity of corrugated rib as the shear connector in composite structures. Corrugated rib is modified as perfobond rib shear connector type to evaluate the shear capacity. A total 12 push-out specimens with stud, perfobond rib, and corrugated rib connector were fabricated. Then, the influences of hole-crossing bars, concrete dowel, depth of corrugated panel and height of rib on the shear capacity were evaluated experimentally. As the results of these tests, the failure mechanisms of corrugated rib and perfobond rib specimens were associated with the bearing failure of the concrete slabs, but the failure of weld zone did not occur. The shear capacity of corrugated rib specimens improved as high to 96% compared to the perfobond rib shear connectors. Also, the hole-crossing bars were effective on the improvement of concrete dowel action, and consequently, shear capacity increased by 48%. It was also proven that the increment of the depth of corrugated panel and the height of rib increased the concrete bearing resistance, therefore increasing the shear capacity.

• Proceedings of the Korean Geotechical Society Conference
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• 2003.03a
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• pp.393-400
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• 2003

지오멤브레인(geomembrane)과 다른 토목섬유, 즉 지오텍스타일 또는 GCL, 사이의 interface 전단거동을 특성화하는 strain-softening 모델을 개발하였다. 본 연구에 제안된 모델은 일차적으로 smooth 지오멤브레인과 textured 지오멤브레인을 대상으로 실시한 직접전단 시험결과를 대상으로 구축되었다. 시험을 통해 측정된 변위-전단응력의 관계는 strain-softening 현상를 고려하기 위해서 최대점이 발생하는 위치를 기준으로, pre-peak과 post-peak 영역으로 나누어 분석을 실시하였다. 실험결과를 토대로 구축된 모델식은 원 자료와의 비교를 통해 본 모델의 유효성을 검증하였다. 비교 결과 높은 연직 응력에서 약간의 차이를 보이긴 하지만, 대체적으로 실험 결과와 구축된 모델을 이용한 역계산의 값이 좋은 일치를 보임을 확인할 수 있었다. 특별히 연직응력이 낮은 단계에서는 높은 일치를 보였는데, 이를 통해 제안된 식이 매립지의 최종 cover와 같이 상재 연직하중이 작은 경우에 지오멤브레인이 포함된 interface의 전단 거동에 대한 합리적인 구성 방정식이 될 수 있음을 확인할 수 있었다.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.225-228
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• 2008

This paper presents out-of-plane shear strength models for composite wall with steel plates based on limit theorem in the framework of the plasticity theory. The formulas proposed by JEAG 4618 need to be reconsidered with a couple of limitations; ignoring the effect of bond stress generated by studs in the process of calculating arch action, illogically discriminating between concrete shear cracking strength and arch strength by algebraic relation in short shear span ratio(0-2.0). In most cases, reinforcement ratio is not sufficient to yield, as a result, arch strength is determined by accounting equilibrium including both bond strength and concrete compressive strength. We conducted experimental research assuming that SC wall is a continuous beam under the simplified loading patterns, changing main valuables involving the number of studs, stirrups. The results show good agreements with the formula and we quoted the test results of JEAG.

• Journal of the Korean Geotechnical Society
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• v.22 no.12
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• pp.67-76
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• 2006

The reasonable assessment of the shear stiffness of a dredged soft ground and soft clay is difficult due to the soil disturbance. This study addresses the development and application of a new in-situ shear wave measuring apparatus (field velocity probe: FVP), which overcomes several of the limitations of conventional methods. Design concerns of this new apparatus include the disturbance of soils, cross-talking between transducers, electromagnetic coupling between cables, self acoustic insulation, the constant travel distance of S-wave, the rotation of the transducer, directly transmitted wave through a frame from transducer to transducer, and protection of the transducer and the cable. These concerns are effectively eliminated by continuous improvements through performing field and laboratory tests. The shear wave velocity of the FVP is simply calculated, without any inversion process, by using the travel distance and the first arrival time. The developed FVP Is tested in soil up to 30m in depth. The experimental results show that the FVP can produce every detailed shear wave velocity profiles in sand and clay layers. In addition, the shear wave velocity at the tested site correlates well with the cone tip resistance. This study suggests that the FVP may be an effective technique for measuring the shear wave velocity in the field to assess dynamic soil properties in soft ground.

• Geotechnical Engineering
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• v.10 no.4
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• pp.67-82
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• 1994

In this study, a reinforced clay model based on the limit equilibrium of forces under direct shear was proposed to predict shear strength increase in clays induced by the steel inclusion. The model accounted for the effects of orientation of inclusion, length, bonding stress between clay and indclusion and passive soil resistance 1 induced by the inclusion movement, on the behavior of reinforced clays. In order to compare with the theoretical predictions, direct shear tests were performed using a direct shear apparatus formed of an open shear box. Also pull-out tests were conducted to determine the bonding stress between the inclusion and clay. From the experimental results, the increase or decrease in shear strength of reinforced clay samples was found to depend on the orientation of inclusionas well as water content of clay samples. From the comparison of theoretical predictions and experimental results, it was found that the theore tical model predicted reasonably well the influence of orientation of the inclusion as well as passive soil resistance induced by the inclusion movement on the mechanical behavior of reinforced clays.

• Journal of the Korea Concrete Institute
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• v.28 no.4
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• pp.419-426
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• 2016

This study examined the effect of transverse reinforcement and compressive stress on the shear friction performance at the shear interface intersecting two structural elements with various concrete types. From the prepared 12 push-off test specimens, various characteristics at the interface were measured as follows: crack propagation, shear load-relative slip relationship, initial shear cracking strength, ultimate shear friction strength, and shear transfer capacity of transverse reinforcement. The configuration of transverse reinforcement and compressive strength of concrete insignificantly influenced the amount of relative slippage at the shear friction plane. With the increase of applied compressive stress, the shear friction capacity of concrete tended to increase proportionally, whereas the shear transfer capacity of transverse reinforcement decreased, which was insignificantly affected by the configuration type of transverse reinforcement. The empirical equations of AASHTO-LRFD and Mattock underestimate the shear friction strength of concrete, whereas Hwang and Yang model provides better reliability, indicating that the mean and standard deviation of the ratios between measured shear strengths and predictions are 1.02 and 0.23, respectively.

• Journal of the Korean Geotechnical Society
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• v.25 no.10
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• pp.41-53
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• 2009

In order to analyze the influence of particle shape on evolution of particle crushing and characteristic of shear behavior of granular soil, direct shear test was simulated by using DEM (Discrete Element Method). Six particle shapes were generated by clump and cluster model built in PFC (Particle Flow Code). The results of direct shear test for six particle shapes were compared and analyzed with those for circular particle shape. The results of numerical tests showed a good agreement with those of experimental tests, thus the appropriateness of numerical modelling set in this study was proved. As for particle shape, more angular and rougher particle induced larger internal friction angle and more particle crushing than relatively round and smooth particle. When particles were crushed, crushing was concentrated on the shear band adjacent to the shear plane. Finally, it can be concluded that the numerical models suggested in this study can be used extensively for other studies concerning the shear behavior of granular soil including soil crushing.