• Computers and Concrete
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• 제22권5호
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• pp.461-468
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• 2018

In this paper, to access the suitability of recycled aggregate for structural applications, concrete strength i.e., compressive, tensile and flexural strength were evaluated and compared with those specimens made of natural aggregates. Test results indicated that 30 to 42% of the mentioned strength decreases. To study the performance of frame structures made of recycled aggregate concrete (RAC) two reinforced RAC frames were prepared and tested under monotonic loading. The joint regions of one of the RAC frame were casted with micro-concrete. A reference specimen was also prepared using natural aggregate concrete (NAC) and subjected to a similar loading condition. The RAC frame resulted in a brittle mode of failure as compared to NAC frame. However, the presence of a micro-concrete at the joint region of an RAC frame improved the damage tolerance and load resisting capacity. Seismic parameter such as energy dissipation, ductility and stiffness also improves. Conclusively, strengthening of joint region using micro-concrete is found to have a significant contribution in improving the seismic performance of an RAC frame.

• 터널과지하공간
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• 제19권3호
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• pp.174-180
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• 2009

This paper gives a brief review of seismicity and seismic monitoring in surface mines. A summary of various researches related to seismicity is presented. Our research focuses on the understanding of seismicity and the application of analytical techniques to seismicity. Seismic monitoring plays an important role in the identification of potential failure planes and thereby predict potential failures. Much of the instrumentation used in our research is derived from earthquake monitoring systems. The major aspects in seismic monitoring are an instrumentation used, size of the network and data acquisition systems. Seismic monitoring in surface mines could be successfully applied to the improvement of safety standards in slope stability.

• 한국지구물리탐사학회:학술대회논문집
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• 한국지구물리탐사학회 2007년도 공동학술대회 논문집
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• pp.291-296
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• 2007

We measured potential waveform of load, displacement, micro electric signal generated by rock and mortar fracture using PXI A/D Converter. The rock type used for measurement was used granite, limestone and sandstone, and mortar specimen. we made measuring equipment of physical properties to confirm basic information of physical properties, measured physical properties of rock engineering, electric resistivity and seismic velocity. Potential waveform system was built using PXI A/D Converter and measured potential waveform of load, displacement, micro-electric signal generated using this during uniaxial compressive test by the specimen finished such test of physical properties. Using the saturated rock and mortar specimen, micro electric signal increased, and It didn't increase a signal in dried rock and mortar specimen according as load and strain rate increases. But signal also increased in saturated or dried specimen in case of sandstone. It was possible to check the close correlation relationship the signal and fracture behavior by a compressive load as the signal of fracture position was increased bigger than the other position. It was also possible to check the correlation relationship between physical properties and micro geo-electric signal.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 추계 학술발표회 제17권2호
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• pp.81-84
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• 2005

In order to effectively resist seismic loads, coupling beams must be sufficiently stiff, strong and posses a stable load-deflection hysteretic response. This paper reports experimental data on the seismic performance of precast HPFRCC coupling beams with variable details. Precast HPFRCC coupling beam was tested to evaluate their failure modes. shear behavior, micro crack pattern and energy dissipation. Based on the experimental results, precast coupling beam with diagonal and rhombic details offer greater performance and ductility than coupling beam with normal detail.

• 한국지진공학회논문집
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• 제17권5호
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• pp.227-235
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• 2013

Friction energy dissipative devices have been increasingly implemented as structural seismic damage protecting systems due to their excellent seismic energy dissipating capacity and high stiffness. This study develops rotational friction energy dissipative devices and verifies experimentally their cyclic response. Based on the understanding of the differences between the traditional linear-motion friction behavior and the rotational friction behavior, the configuration of the frictional surface was determined by investigating the characteristics of the micro-friction behavior. The friction surface suggested in this paper consists of brake-lining pads and stainless steel sheets and is normally stressed by high-strength bolts. Based upon these frictional characteristics of the selected interface, the rotational friction energy dissipative devices were developed. Bolt torque-bearing force tests, rotational friction tests of the suggested friction interfaces were carried out to identify their frictional behavior. Test results show that the bearing force is almost linearly proportional to the applied bolt torque and presents stable cyclic response regardless of the experimental parameters selected this testing program. Finally, cyclic tests of the rotational friction energy dissipative devices were performed to find out their structural characteristics and to confirm their stable cyclic response. The developed friction energy dissipative devices present very stable cyclic response and meet the requirements for displacement-dependent energy dissipative devices prescribed in ASCE/SEI 7-10.

• 한국가스학회지
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• 제20권1호
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• pp.13-22
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• 2016

본 연구에서는 다단계 수압파쇄와 수평시추가 적용된 셰일가스정에서 생산자료의 유동형태에 따라 적절한 분석 방법과 궁극가채량을 산출하는 기법을 결정하는 방법을 정리한 흐름도를 제안하였다. 또한 1차 천이유동만이 나타나는 현장자료에 대해 생산천이유동 분석을 수행할 때 고려해야 하는 사항들을 제안하였다. log-log 그래프와 시간제곱근 그래프 분석을 통해 생산자료의 유동 특성을 분류할 수 있고, 이 결과, 1차 천이유동만이 나타나는 생산자료는 이 유동이 종료되는 시점을 정확히 예측하여 이 시점을 기준으로 생산성을 각각 예측하여야 한다. 이 시점은 미세탄성파 탐사자료 해석을 통해 균열자극부피의 면적을 계산함으로써 산출할 수 있다. 공저압력자료나 미세탄성파 탐사자료가 없다면 셰일가스정에 적절한 경험적 방법을 활용하여 생산성을 예측할 수 있다. 생산기간이 짧은 자료는 상대적으로 생산기간이 긴 인접 생산정의 자료를 활용하여 생산기간의 적절성을 평가한 후 필요하다면 생산초기 자료를 제외하고 분석하는 것이 정확도를 향상시킬 수 있다. 또한 미세탄성파 탐사자료 해석에 의해 산출된 SRV는 분석방법이나 분석자의 주관에 의해 과대, 과소 평가될 수 있기 때문에 파쇄 단계, 파쇄유체 주입량, 생산성 분석을 통한 적절성평가를 수행하여 필요한 경우, 저류층 시뮬레이션, 균열모델링, 생산천이분석을 통해 재산정하는 것이 필요하다.

• Steel and Composite Structures
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• 제43권5호
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• pp.565-579
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• 2022

This study investigated the yielding capacity and performance of seismic dampers constructed with steel ring plates using numerical and analytical approaches. This study aims to provide an analytical relationship for estimating the yielding capacity and initial stiffness of steel ring dampers. Using plastic analysis and considering the mechanism of plastic hinge formation, a relation has been obtained for estimating the yielding capacity of steel ring dampers. Extensive parametric studies have been carried out using a nonlinear finite element method to examine the accuracy of the obtained analytical relationships. The parametric studies include investigating the influence of the length, thickness, and diameter of the ring of steel ring dampers. To this end, comprehensive verification studies are performed by comparing the numerical predictions with several reported experimental results to demonstrate the numerical method's reliability and accuracy. Comparison is made between the hysteresis curves, and failure modes predicted numerically or obtained/observed experimentally. Good agreement is observed between the numerical simulations and the analytical predictions for the yielding force and initial stiffness. The difference between the numerical models' ultimate tensile and compressive capacities was observed that average of about 22%, which stems from the performance of the ring-dampers in the tensile and compression zones. The results show that the steel ring-dampers are exhibited high energy dissipation capacity and ductility. The ductility parameters for steel ring-damper between values were 7.5 to 4.1.

• Structural Monitoring and Maintenance
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• 제5권2호
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• pp.205-229
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• 2018

Energy induced by minor earthquake and micro vibration cannot be dissipated by traditional buckling-restrained braces (BRBs). To solve this problem, a new type of hybrid passive control device, named as VE-BRB, which is configured by a BRB with high-damping viscoelastic (VE) layers, is developed and studied. Theoretical analysis, performance tests, numerical simulation and case analysis are conducted to study the seismic behavior of VE-BRBs. The results indicate that the combination of hysteretic and damping devices lead to a multi-phased nature and good performance. VE-BRB's working state can be divided into three phases: before yielding of the steel core, VE layers provide sufficient damping ratio to mitigate minor vibrations; after yielding of the steel core, the steel's hysteretic deformations provide supplemental dissipative capacity for structures; after rupture of the steel core, VE layers are still able to work normally and provide multiple security assurance for structures. The simulation results agreed well with the experimental results, validating the finite element analysis method, constitutive models and the identified parameters. The comparison of the time history analysis on a 6-story frame with VE-BRBs and BRBs verified the advantages of VE-BRB for seismic protection of structures compared with traditional BRB. In general, VE-BRB had the potential to provide better control effect on structural displacement and shear in all stages than BRB as expected.

• 지구물리와물리탐사
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• 제13권3호
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• pp.286-294
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• 2010

한국지질자원연구원은 광역 지진관측망 이외에도 7 개소의 지진-음파(인프라사운드) 관측소를 설치하여 운영하고 있다. 이들 배열식 지진-음파 관측소는 지진파 이외에도 원거리 음원에서 발생하는 인프라사운드 신호를 관측할 수 있다. 인프라사운드란 대기권을 전파하는 20 Hz 이하 저주파수 음파로 정의되며, 에너지 감쇠가 적어 장거리를 전파하기 때문에 원거리에서 관측이 가능하다. 국내 인프라사운드 관측기술은 우선적으로 자연지진과 인공지진(지표발파)을 식별하기 위해 도입되었다. 지난 10여 년간 국내 인프라사운드 관측소를 운영한 결과 지진원 식별이외에도 다양한 지구물리학적 자연현상과 북한의 핵실험 등 인위적 폭발현상에서 발생한 인프라사운드를 관측할 수 있었다. 본 연구에서는 국내 인프라사운드 관측소를 통해 한반도 및 주변지역에서 발생한 주요 인프라사운드 음원에 대한 관측사례와 연구결과를 소개하고자 한다. 결론적으로, 인프라사운드 관측기술은 기존 대기에 국한된 관측영역을 넓혀 지구내부-지표면-대기권에서 발생하는 다양한 자연 혹은 인위적 현상을 관측하고 분석할 수 있는 새로운 지구관측기술의 하나로 자리 잡고 있다. 향후 지진파와 인프라사운드를 융합한 탐지, 분석기술 개발은 자연현상에 대한 지구물리학적 이해를 넓히고 인위적 폭발현상에 대한 원거리 정밀탐지기술로 응용이 가능하리라 판단된다.

• 터널과지하공간
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• 제26권2호
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• pp.59-67
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• 2016

본 논문에서는 해저 하이드레이트 퇴적층에서의 메탄가스 생산 과정에서 발생 가능한 생산정 주변 단층의 재활성화 가능성을 수치해석을 통해 평가하고 재활성화에 따른 미소지진 규모를 예측한 결과를 소개하였다. 가스 생산에 의한 하이드레이트 퇴적층의 유효응력 변화 및 역학적 변형은 TOUGH+Hydrate 코드와 FLAC3D 코드를 순차적으로 연계해석함으로써 시뮬레이션하였다. 단층면 재활성화 기준은 모어쿨롱(Mohr-Coulomb)법칙이 유효한 것으로 가정하였다. 30일간의 시험생산 해석 결과, 감압에 의한 공극압력 감소 및 유효응력의 증가가 주변 단층의 활성화를 일으킬 가능성은 크지 않은 것으로 나타났다. 초기응력 조건에 따른 활성화 가능성을 활동마찰각으로 평가한 결과로부터 수평응력에 비해 수직응력이 상대적으로 큰 정단층 응력조건(normal fault stress regime)에서 단층 재활성화 가능성이 상대적으로 큰 것으로 파악되었다. 또한, 정단층 응력조건에서 단층 재활성화에 기인한 유도지진 발생규모를 모멘트 크기(moment magnitude)로 추정할 경우, 모두 음(-)의 값을 보여 인간이 감지하지 어려운 수준의 미소지진에 해당하는 결과를 보였다. 다만, 본 해석은 하이드레이트 생산과정에서의 단층재활성화 가능성 평가를 목적으로 한 해석기법 구축 및 그 적용성을 소개할 목적으로 상당히 단순화된 지질구조 모델을 가정한 결과이므로, 향후 하이드레이트 시험 생산 및 상업 생산 지역에서의 상세 지질구조, 입력 물성 및 생산 설계조건을 반영한 해석에서는 상이한 결과를 보일 수 있을 것이다.