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- 저자 : Md Samdani Azad (검색결과 6 건)
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Nguyen, Duy-Duan,Thusa, Bidhek,Park, Hyosang,Azad, Md Samdani,Lee, Tae-Hyung Korean Nuclear Society 2021 Nuclear Engineering and Technology Vol.53 No.8
The purpose of this study is to investigate the efficiency of various structural modeling schemes for evaluating seismic performances and fragility of the reactor containment building (RCB) structure in the advanced power reactor 1400 (APR1400) nuclear power plant (NPP). Four structural modeling schemes, i.e. lumped-mass stick model (LMSM), solid-based finite element model (Solid FEM), multi-layer shell model (MLSM), and beam-truss model (BTM), are developed to simulate the seismic behaviors of the containment structure. A full three-dimensional finite element model (full 3D FEM) is additionally constructed to verify the previous numerical models. A set of input ground motions with response spectra matching to the US NRC 1.60 design spectrum is generated to perform linear and nonlinear time-history analyses. Floor response spectra (FRS) and floor displacements are obtained at the different elevations of the structure since they are critical outputs for evaluating the seismic vulnerability of RCB and secondary components. The results show that the difference in seismic responses between linear and nonlinear analyses gets larger as an earthquake intensity increases. It is observed that the linear analysis underestimates floor displacements while it overestimates floor accelerations. Moreover, a systematic assessment of the capability and efficiency of each structural model is presented thoroughly. MLSM can be an alternative approach to a full 3D FEM, which is complicated in modeling and extremely time-consuming in dynamic analyses. Specifically, BTM is recommended as the optimal model for evaluating the nonlinear seismic performance of NPP structures. Thereafter, linear and nonlinear BTM are employed in a series of time-history analyses to develop fragility curves of RCB for different damage states. It is shown that the linear analysis underestimates the probability of damage of RCB at a given earthquake intensity when compared to the nonlinear analysis. The nonlinear analysis approach is highly suggested for assessing the vulnerability of NPP structures.
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응웬두이두안(Nguyen, Duy-Duan),삼다니아자드(Azad, Md Samdani),최병호(Choi Byung H.),이태형(Lee, Tae-Hyung) 한국방재학회 2020 한국방재학회논문집 Vol.20 No.6
본 논문의 목적은 일체형교대교량의 지진취약도를 평가하는데 적합한 지진강도지표(IM)를 판별하는 것이다. 90개의 지진가속도기록과 20가지 IM을 고려한 비선형시간이력해석을 수행하여 교각의 횡방향변위를 관찰하였다. 교량의 내진성능과 상관도가높은 IM을 판별하기 위해 결정계수, 표준편차, 상관계수 등 다양한 통계인자를 고려하였다. 수치해석결과 상관도가 높은IM은 고유주기에서의 스펙트럼가속도, 스펙트럼속도, 스펙트럼변위와 ASI, EPA, PGA, A95 등으로 나타났다. 상관도가 높은IM를 기준으로 한 교량의 지진취약도곡선을 도출하였다. The purpose of this study is to identify efficient earthquake intensity measures (IMs) for evaluating the seismic vulnerability of integral abutment bridges. A total of 90 ground motion records and 20 typical IMs were employed for the numerical analyses. A series of nonlinear time-history analyses was performed on the bridges to observe the lateral displacement of the bridge piers. Statistical parameters such as the coefficient of determination, standard deviation, and correlation coefficient were calculated to identify the strongly correlated IMs with the seismic performance of the bridges. The numerical results show that the efficient IMs are spectral acceleration, spectral velocity, spectral displacement at the fundamental period, acceleration spectrum intensity, effective peak acceleration, peak ground acceleration, and A95. Moreover, a set of fragility curves of the bridges was developed with respect to the efficient IMs.
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Duy-Duan Nguyen,Bidhek Thusa,Md Samdani Azad,Viet-Linh Tran,이태형 한국원자력학회 2021 Nuclear Engineering and Technology Vol.53 No.12
This study identifies efficient earthquake intensity measures (IMs) for seismic performances and fragilityevaluations of the reactor containment building (RCB) in the advanced power reactor 1400 (APR1400)nuclear power plant (NPP). The computational model of RCB is constructed using the beam-truss model(BTM) for nonlinear analyses. A total of 90 ground motion records and 20 different IMs are employed fornumerical analyses. A series of nonlinear time-history analyses are performed to monitor maximum floordisplacements and accelerations of RCB. Then, probabilistic seismic demand models of RCB are developedfor each IM. Statistical parameters including coefficient of determination (R2), dispersion (i.e. standarddeviation), practicality, and proficiency are calculated to recognize strongly correlated IMs with theseismic performance of the NPP structure. The numerical results show that the optimal IMs are spectralacceleration, spectral velocity, spectral displacement at the fundamental period, acceleration spectrumintensity, effective peak acceleration, peak ground acceleration, A95, and sustained maximum acceleration. Moreover, weakly related IMs to the seismic performance of RCB are peak ground displacement,root-mean-square of displacement, specific energy density, root-mean-square of velocity, peak groundvelocity, Housner intensity, velocity spectrum intensity, and sustained maximum velocity. Finally, a set offragility curves of RCB are developed for optimal IMs.
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Thusa Bidhek,Nguyen Duy-Duan,Azad Md Samdani,이태형 한국원자력학회 2023 Nuclear Engineering and Technology Vol.55 No.5
The reactor containment building (RCB) in nuclear power plants (NPPs) plays an important role in protecting the reactor systems from external loads as well as preventing radioactive leaking. As we witnessed the nuclear disaster at Fukushima Daiichi (Japan) in 2011, the earthquake is one of the major threats to NPPs. The purpose of this study is to evaluate effects of concrete material models and presstressing forces on the seismic performance evaluation of RCB in NPPs. A typical RCB designed in Korea is employed for a case study. Detailed three-dimensional nonlinear finite element models of RCB are developed in ANSYS. A series of pushover analyses are then performed to obtain the pushover curves of RCB. Different capacity curves are compared to recognize the influence of different material models on the nonlinear behavior of RCB. Additionally, the effects of prestressing forces on the seismic performances of the structure are also investigated. Moreover, a set of damage states corresponding to damage evolutions of the structures is proposed in this study.
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