탄성파 속성 분석을 위한 탄성파 자료 무작위 잡음 제거 연구

원종필,신정균,하지호,전형구 대한자원환경지질학회 2024 자원환경지질 Vol.57 No.1

탄성파 탐사는 지하자원 개발, 지반 조사, 지층 모니터링 등에 널리 사용되고 있는 지구물리탐사 방법으로 정확한 지층 구조 영상을 제공해주기 때문에 지층의 지질학적 특성 해석에 필수적으로 활용된다. 일반적으로는 탄성파 구조 보정 영상을 시각적으로 분석하여 지질학적 특성을 해석하지만 최근에는 탄성파 구조 보정 자료에 대한 정량적인 분석을 통해 원하는 지질학적 특성을 정확하게 추출하고 해석하는 탄성파 속성 분석이 널리 연구되고 있다. 탄성파 속성 분석은 탄성파 자료에 기반한 지질학적 해석에 정량적인 근거를 제시해줄 수 있기 때문에 석유 및 가스 저류층 분석, 단층 및 균열대 조사, 지층 가스 분포 파악 등의 다양한 분야에서 활용되고 있다. 하지만 탄성파 속성 분석은 탄성파 자료 내 잡음에 취약하므로 속성 분석의 정확도 향상을 위해서는 중합 후 탄성파 자료에 대한 추가적인 잡음 제거가 수반되어야 한다. 본 연구에서는 중합 후 탄성파 자료에 대한 무작위 잡음 제거 및 및 탄성파 속성 분석 정확도 개선을 위해 4가지의 잡음 제거 방법을 적용하고 비교한다. FX 디콘볼루션, DSMF, Noise2Noiose, DnCNN을 각각 포항 영일만 고해상 탄성파 자료에 적용하여 탄성파 무작위 잡음을 제거하고 잡음이 제거된 탄성파 자료로부터 에너지, 스위트니스, 유사도 속성을 계산한다. 그리고 각 잡음 제거 방법의 특성, 잡음 제거 결과, 탄성파 속성 분석 결과를 정성적 및 정량적으로 분석한 후, 이를 기반으로 탄성파 속성 분석 결과 향상을 위한 최적의 잡음 제거 방법을 제안한다. Seismic exploration is one of the widely used geophysical exploration methods with various applications such as resource development, geotechnical investigation, and subsurface monitoring. It is essential for interpreting the geological characteristics of subsurface by providing accurate images of stratum structures. Typically, geological features are interpreted by visually analyzing seismic sections. However, recently, quantitative analysis of seismic data has been extensively researched to accurately extract and interpret target geological features. Seismic attribute analysis can provide quantitative information for geological interpretation based on seismic data. Therefore, it is widely used in various fields, including the analysis of oil and gas reservoirs, investigation of fault and fracture, and assessment of shallow gas distributions. However, seismic attribute analysis is sensitive to noise within the seismic data, thus additional noise attenuation is required to enhance the accuracy of the seismic attribute analysis. In this study, four kinds of seismic noise attenuation methods are applied and compared to mitigate random noise of poststack seismic data and enhance the attribute analysis results. FX deconvolution, DSMF, Noise2Noise, and DnCNN are applied to the Youngil Bay high-resolution seismic data to remove seismic random noise. Energy, sweetness, and similarity attributes are calculated from noise-removed seismic data. Subsequently, the characteristics of each noise attenuation method, noise removal results, and seismic attribute analysis results are qualitatively and quantitatively analyzed. Based on the advantages and disadvantages of each noise attenuation method and the characteristics of each seismic attribute analysis, we propose a suitable noise attenuation method to improve the result of seismic attribute analysis.

핵연료집합체 비탄성 내진해석 방법론에 대한 국내외 기술 개발 동향 분석

이미연(Mi-Yeon Lee),남현석(Hyun-Suk Nam),김태순(Tae-Soon Kim) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.4

동일본대지진 이후, 원자력발전소 내진에 대한 안전성을 강화하는 연구가 활발하게 진행되고 있다. 이러한 연구결과를 바탕으로, 국내∙외 원자력규제기관에서도 내진평가 기준을 상향 요구하고 있다. 내진 설계 기준에 따라 기존 내진평가 시에는 탄성해석만을 고려하고 있다. 하지만, 탄성해석의 과도한 보수성 완화를 위해 비탄성 해석을 고려하는 다양한 연구가 수행되고 있다. 따라서, 본 연구에서는 핵연료집합체에 대한 해외 비탄성 내진해석 방법론 및 국내에서 개발중인 설계기준초과지진 조건에서의 핵연료집합체 내진해석 방법론에 대해 소개하였다. 프랑스 AREVA 에서는 CASAC 코드를 사용하여 US-EPR 핵연료집합체 모델에 비탄성 내진해석을 수행하였다. 일본 Mitsubishi 에서는 FINDS 코드를 사용하여 US-APWR 핵연료집합체 모델에 비탄성 내진해석을 수행하였고, 비탄성 모델을 검증하기 위한 시험도 수행하였다. 국내에서는 한국수력원자력과 유관기관에서 핵연료집합체 내진해석 고유방법론을 개발하고 있는 중이다. 개발된 코드는 설계기준초과지진 조건에서 핵연료집합체 비탄성 내진해석에 적용하여 과도한 보수성을 제거하고 이에 따라 내진여유도를 추가 확보하고자 한다. 본 논문에서는 핵연료집합체 비탄성 내진해석 방법론에 대한 해외 사례를 설명하고, 국내에서 개발 중인 고유 방법론의 동향을 파악하였다. Since the great east Japan earthquake, research related to strengthen the safety of Nuclear Power Plants (NPP) is widely conducted. Based on these research results, nuclear regulatory agencies require enhanced seismic evaluation standards. According to the current seismic design, the seismic evaluation is performed based on the elastic analysis. However, research based on inelastic analysis is performed to reduce the conservatism of elastic analysis. Therefore, inelastic seismic analysis methodologies for fuel assembly developed by other countries and a developing methodology for seismic analysis under beyond design basis earthquake (BDBE) in Korea are introduced in this paper. In AREVA (France), inelastic seismic analysis was performed on the US-EPR fuel assembly using CASAC code. Also, FINDS code was used for inelastic seismic analysis of US-APWR fuel assembly and experiment was performed to verify the inelastic model in Mitsubishi (Japan). In Korea, KHNP and related companies are developing a methodology for fuel assembly seismic analysis. This code will be applied to inelastic seismic analysis of fuel assembly under BDBE condition to reduce the conservatism of elastic analysis and to secure an additional seismic margins. This paper introduce fuel assembly inelastic seismic analysis methodologies developed by other countries and the trend of the fuel assembly seismic analysis methodology developed in Korea.

원자력발전소 지진 PSA의 계통분석방법 개선 연구

임학규 한국안전학회 2019 한국안전학회지 Vol.34 No.5

The seismic PSA is to probabilistically estimate the potential damage that a large earthquake will cause to a nuclear power plant. It integrates the probabilistic seismic hazard analysis, seismic fragility analysis, and system analysis and is utilized to identify seismic vulnerability and improve seismic capacity of nuclear power plants. Recently, the seismic risk of domestic multi-unit nuclear power plant sites has been evaluated after the Great East Japan Earthquake and Gyeongju Earthquake in Korea. However, while the currently available methods for system analysis can derive basic required results of seismic PSA, they do not provide the detailed results required for the efficient improvement of seismic capacity. Therefore, for in-depth seismic risk evaluation, improved system analysis method for seismic PSA has become necessary. This study develops a system analysis method that is not only suitable for multi-unit seismic PSA but also provides risk information for the seismic capacity improvements. It will also contribute to the enhancement of the safety of nuclear power plants by identifying the seismic vulnerability using the detailed results of seismic PSA. In addition, this system analysis method can be applied to other external event PSAs, such as fire PSA and tsunami PSA, which require similar analysis.

Seismic analysis of the APR1400 nuclear reactor system using a verified beam element model

Park, Jong-beom,Park, No-Cheol,Lee, Sang-Jeong,Park, Young-Pil,Choi, Youngin Elsevier 2017 Nuclear engineering and design Vol.313 No.-

<P><B>Abstract</B></P> <P>Structural integrity is the first priority in the design of nuclear reactor internal structures. In particular, nuclear reactor internals should be designed to endure external forces, such as those due to earthquakes. Many researchers have performed finite element analyses to meet these design requirements. Generally, a seismic analysis model should reflect the dynamic characteristics of the target system. However, seismic analysis based on the finite element method requires long computation times as well as huge storage space. In this research, a beam element model was developed and confirmed based on the real dynamic characteristics of an advanced pressurized water nuclear reactor 1400 (APR1400) system. That verification process enhances the accuracy of the finite element analysis using the beam elements, remarkably. Also, the beam element model reduces seismic analysis costs. Therefore, the beam element model was used to perform the seismic analysis. Then, the safety of the APR1400 was assessed based on a seismic analysis of the time history responses of its structures. Thus, efficient, accurate seismic analysis was demonstrated using the proposed beam element model.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A simplified beam element model is constructed based on the real dynamic characteristics of the APR1400. </LI> <LI> Time history analysis is performed to calculate the seismic responses of the structures. </LI> <LI> Large deformations can be observed at the in-phase mode of reactor vessel and core support barrel. </LI> </UL> </P>

단순화 모델에서의 응답스펙트럼과 시간이력 내진해석 결과를 활용한 해양플랜트용 매니폴드 실제품의 내진강도 평가

이은호,곽시영 한국전산구조공학회 2019 한국전산구조공학회논문집 Vol.32 No.1

In this paper, for a seismic analysis of an offshore subsea manifold, Response Spectrum Analysis(RSA) and Time History Analysis(THA) were conducted under a various analysis conditions. Response spectrum and seismic design procedure have followed ISO19901-2 code. In case of THA, The response spectrum were converted into artificial earthquake history and both of Explicit and Implicit solvers were used to examine the characteristics of seismic analysis. For the verification, Various seismic analysis methods were applied on a single degree of freedom beam model and a simplified model of the actual manifold. The difference between the results of RSA and THA on the simplified manyfold model evaluated for the analysis of the actual manifold. Because THA is impossible in case of real complex structure such as a manifold, Safety of the actual manifold structure was accessed by using the RSA and the difference between the results of RSA and THA from the simplified model. 본 논문에서는 해양플랜트용 매니폴드 구조물의 내진해석을 위해, 단순화 모델에 대해 응답스펙트럽해석(RSA) 및 시간이력해석(THA)을 여러 조건으로 진행하여 비교 검토하였다. 응답스펙트럼해석은 ISO19901-2에 따른 내진설계 절차를 이용하였다. 시간이력해석의 경우, 응답스펙트럼으로 가속도와 변위에 대한 지진이력을 인공적으로 만든뒤 Explicit와 Implicit 솔버를 사용하여 해석하였다. 단자유도 모델을 사용하여 해석방법을 검증하였으며, 매니폴드 구조물을 단순화한 모델에서 시간이력해석과 응답스펙트럼해석법의 차이를 분석하였다. 복잡한 실제 구조물에 대해서 직접적인 시간이력해석은 불가능하므로 응답스펙트럼해석법을 적용하였고, 단순화 모델에서 분석한 결과 차이를 활용하여 실제 구조물의 안전성을 판단하였다.

Seismic Vulnerability Analysis of Multi-main-span High Pier Continuous Rigid-frame Bridge in Terms of Cloud Method

Jingang Zhao,Hongyu Jia,Yulin Zhan 대한토목학회 2023 KSCE Journal of Civil Engineering Vol.27 No.6

Due to the complex canyon topography in southwestern regions of China, several multi-main-span high pier continuous rigid-frame bridges (MHPCRFBs) are built to meet the special terrain. Owing to the great effect of high-order modes, the seismic responses of MHPCRFBs are more complicated than the conventional signal main span continuous rigid-frame bridges. However, there has been very limited researches focus on the seismic vulnerability of MHPCRFBs. This study selects a practical five-span (three main span) high pier continuous rigid-frame bridge as a study object to investigate the seismic vulnerability of MHPCRFBs under near-field pulse-like seismic wave excitation. And a finite element model of the example bridge is built by OpenSees incorporating the influence of abutment, and simultaneously100 near-field pulse-like seismic waves are chosen to research their effect on the seismic vulnerability of the MHPCRFB. The dynamic nonlinear time-history analyses are carried out to record the peak demand values of the example bridge under three seismic excitation calculation cases (longitudinal earthquake, biaxial earthquake, and triaxial earthquake). Thirty-three intensity measures are compared with respect to two statistical parameters including correlation efficient and root mean square error, the peak ground velocity (PGV) turns out to be the optimal intensity measure for seismic vulnerability analysis of MHPCRFB. Subsequently, by using the analysis procedures of the cloud method, the seismic vulnerability curves of MHPCRFB are developed and compared. The results of this study show that the bottom and top areas of the high piers are more fragile at the slight and moderate damage stages along longitudinal direction, and only the bottom areas are prone to damage along transverse direction. And the seismic wave excitation directions have an obvious influence on the seismic damage probability of the MHPCRFB. In addition, the zone with larger failure probabilities of the lower pier is significantly longer than the higher pier. The obtained results provide helpful reference for the seismic-resistant design and consolidation of MHPCRFBs, shed light on the lower pier of MHPCRFBs should be paid high concern to the anti-seismic design.

터널 횡방향 지진해석 Part II: 동적해석을 통한 터널의 지진응답 예측 한국지반공학회논문집 제26권 제6호터널 횡방향 지진해석 Part II: 동적해석을 통한 터널의 지진응답 예측

박두희,신종호,윤세웅 한국지반공학회 2010 한국지반공학회논문집 Vol.26 No.6

Dynamic analyses of tunnels are widely performed in practice in Korea. Accurate performance of a dynamic analysis is very difficult, requiring appropriate application of lower and lateral boundary conditions, deconvolution, constitutive model, and selection of dynamic soil properties etc. Lack of a systematic guideline on how to perform the dynamic analysis makes it even more difficult to perform an analysis. In addition, dynamic analyses are not needed in most cases and pseudo-static analyses are more than adequate. However, they are performed without a clear understanding on the need for the dynamic analysis and differences between the two methods. In this study, firstly, a guideline for correctly performing a 2D dynamic analysis is developed. Secondly, the differences in the tunnel responses using dynamic and pseudo-static analyses are discussed and compared. The results show that the discrepancies between the dynamic and static analyses are not significant for most cases. It is therefore recommended that the dynamic analyses be performed at tunnel portal, very soft ground, or in cases where spatial variation of the ground motion needs to be considered in the seismic analysis of tunnels in transverse direction.

Efficient seismic analysis of multi-story buildings

Lee, Dong Guen,Kim, Hee Cheul Techno-Press 1996 Structural Engineering and Mechanics, An Int'l Jou Vol.4 No.5

The equivalent static force procedure and the response spectrum analysis method are widely used for seismic analyses of multi-story buildings. The equivalent static force procedure is one of the most simple but less accurate method in predicting possible seismic response of a structure. The response spectrum analysis method provides more accurate results while it takes much longer computational time. In the response spectrum method, dynamic response of a multi-story building is obtained by combining modal responses through a proper procedure such as SRSS or CQC method. Since all of the analysis results are expressed in absolute values, structural engineers have difficulties to combine them with the results obtained from the static analysis. Design automation is interrupted at this stage because of the difficulty in the decision of the most critical design load. Pseudo-dynamic analysis method proposed in this study provides more accurate seismic analysis results than those of the equivalent static force procedure since the dynamic characteristics of a structure is considered. And the proposed method has an advantage in combination of the analysis results due to gravity loads and seismic loads since the direction of the forces can be considered.

진동대 모형 실험과 3차원 수치해석을 통한 농업용 저수지의 내진안정성 분석

송창섭, 김명환, 우제근 忠北大學校 農業科學硏究所 2017 農業科學硏究 Vol.33 No.1

The object of this paper was to determine seismic safety of agricultural reservoir. This study was carried out to analysis for the displacement characteristic and seismic acceleration characteristic. This study compare and evaluated the results of shaking table tests and 3-D Numerical analysis. As a result of the shaking table test, acceleration increased 10% after the installation in the short period seismic wave toward the center of levee, The maximum displacement was 11.98 mm in long - term seismic wave, and the permissible shipment variation was corrected to be less than 1% and 220 mm in ‘Assessment and improvement of seismic performance of existing dam’. As a result of 3-D Numerical analysis by combined load of railway vibration load and ground acceleration, the acceleration increased by maximum 2.97 times from bedrock acceleration 0.154 g in short period and long period seismic wave, The displacement was found to be 79.6 mm above the bank in the long - term seismic wave after construction, and the permanent displacement was 11.5 mm in the railway. 3-D Numerical analysis results showed ‘Assessment and improvement of seismic performance of existing dam’ as well as shaking table model test. Further research is needed on the combined action of railway and seismic loads for the seismic stability of agricultural reservoirs.

Seismic fragility assessment of isolated structures by using stochastic response database

Eem, Seung-Hyun,Jung, Hyung-Jo Techno-Press 2018 Earthquakes and structures Vol.14 No.5

The seismic isolation system makes a structure isolated from ground motions to protect the structure from seismic events. Seismic isolation techniques have been implemented in full-scale buildings and bridges because of their simplicity, economic effectiveness, inherent stability and reliability. As for the responses of an isolated structure due to seismic events, it is well known that the most uncertain aspects are the seismic loading itself and structural properties. Due to the randomness of earthquakes and uncertainty of structures, seismic response distributions of an isolated structure are needed when evaluating the seismic fragility assessment (or probabilistic seismic safety assessment) of an isolated structure. Seismic response time histories are useful and often essential elements in its design or evaluation stage. Thus, a large number of non-linear dynamic analyses should be performed to evaluate the seismic performance of an isolated structure. However, it is a monumental task to gather the design or evaluation information of the isolated structure from too many seismic analyses, which is impractical. In this paper, a new methodology that can evaluate the seismic fragility assessment of an isolated structure is proposed by using stochastic response database, which is a device that can estimate the seismic response distributions of an isolated structure without any seismic response analyses. The seismic fragility assessment of the isolated nuclear power plant is performed using the proposed methodology. The proposed methodology is able to evaluate the seismic performance of isolated structures effectively and reduce the computational efforts tremendously.