PROBABILISTIC SEISMIC ASSESSMENT OF BASE-ISOLATED NPPS SUBJECTED TO STRONG GROUND MOTIONS OF TOHOKU EARTHQUAKE

Ali, Ahmer,Hayah, Nadin Abu,Kim, Dookie,Cho, Ung Gook Korean Nuclear Society 2014 Nuclear Engineering and Technology Vol.46 No.5

The probabilistic seismic performance of a standard Korean nuclear power plant (NPP) with an idealized isolation is investigated in the present work. A probabilistic seismic hazard analysis (PSHA) of the Wolsong site on the Korean peninsula is performed by considering peak ground acceleration (PGA) as an earthquake intensity measure. A procedure is reported on the categorization and selection of two sets of ground motions of the Tohoku earthquake, i.e. long-period and common as Set A and Set B respectively, for the nonlinear time history response analysis of the base-isolated NPP. Limit state values as multiples of the displacement responses of the NPP base isolation are considered for the fragility estimation. The seismic risk of the NPP is further assessed by incorporation of the rate of frequency exceedance and conditional failure probability curves. Furthermore, this framework attempts to show the unacceptable performance of the isolated NPP in terms of the probabilistic distribution and annual probability of limit states. The comparative results for long and common ground motions are discussed to contribute to the future safety of nuclear facilities against drastic events like Tohoku.

Design response spectra-compliant real and synthetic GMS for seismic analysis of seismically isolated nuclear reactor containment building

Ahmer Ali,NADIN ABU HAYAH,김두기,조성국 한국원자력학회 2017 Nuclear Engineering and Technology Vol.49 No.4

Due to the severe impacts of recent earthquakes, the use of seismic isolation is paramount for the safetyof nuclear structures. The diversity observed in seismic events demands ongoing research to analyze thedevastating attributes involved, and hence to enhance the sustainability of base-isolated nuclear powerplants. This study reports the seismic performance of a seismically-isolated nuclear reactor containmentbuilding (NRCB) under strong short-period ground motions (SPGMs) and long-period ground motions(LPGMs). The United States Nuclear Regulatory Commission-based design response spectrum for theseismic design of nuclear power plants is stipulated as the reference spectrum for ground motion selection. Within the period range(s) of interest, the spectral matching of selected records with the targetspectrum is ensured using the spectral-compatibility approach. NRC-compliant SPGMs and LPGMs fromthe mega-thrust Tohoku earthquake are used to obtain the structural response of the base-isolated NRCB. To account for the lack of earthquakes in low-to-moderate seismicity zones and the gap in the artificialsynthesis of long-period records, wavelet-decomposition based autoregressive moving average modelingfor artificial generation of real ground motions is performed. Based on analysis results from real andsimulated SPGMs versus LPGMs, the performance of NRCBs is discussed with suggestions for futureresearch and seismic provisions.

MODELING OF NONLINEAR CYCLIC LOAD BEHAVIOR OF I-SHAPED COMPOSITE STEEL-CONCRETE SHEAR WALLS OF NUCLEAR POWER PLANTS

Ali, Ahmer,Kim, Dookie,Cho, Sung Gook Korean Nuclear Society 2013 Nuclear Engineering and Technology Vol.45 No.1

In recent years steel-concrete composite shear walls have been widely used in enormous high-rise buildings. Due to high strength and ductility, enhanced stiffness, stable cycle characteristics and large energy absorption, such walls can be adopted in the auxiliary building; surrounding the reactor containment structure of nuclear power plants to resist lateral forces induced by heavy winds and severe earthquakes. This paper demonstrates a set of nonlinear numerical studies on I-shaped composite steel-concrete shear walls of the nuclear power plants subjected to reverse cyclic loading. A three-dimensional finite element model is developed using ABAQUS by emphasizing on constitutive material modeling and element type to represent the real physical behavior of complex shear wall structures. The analysis escalates with parametric variation in steel thickness sandwiching the stipulated amount of concrete panels. Modeling details of structural components, contact conditions between steel and concrete, associated boundary conditions and constitutive relationships for the cyclic loading are explained. Later, the load versus displacement curves, peak load and ultimate strength values, hysteretic characteristics and deflection profiles are verified with experimental data. The convergence of the numerical outcomes has been discussed to conclude the remarks.

Modeling of Nonlinear Cyclic Load Behavior of I-shaped Composite Steel-Concrete Shear Walls of Nuclear Power Plants

AHMER ALI,김두기,조성국 한국원자력학회 2013 Nuclear Engineering and Technology Vol.45 No.1

In recent years steel-concrete composite shear walls have been widely used in enormous high-rise buildings. Due to high strength and ductility, enhanced stiffness, stable cycle characteristics and large energy absorption, such walls can be adopted in the auxiliary building; surrounding the reactor containment structure of nuclear power plants to resist lateral forces induced by heavy winds and severe earthquakes. This paper demonstrates a set of nonlinear numerical studies on I-shaped composite steel-concrete shear walls of the nuclear power plants subjected to reverse cyclic loading. A three-dimensional finite element model is developed using ABAQUS by emphasizing on constitutive material modeling and element type to represent the real physical behavior of complex shear wall structures. The analysis escalates with parametric variation in steel thickness sandwiching the stipulated amount of concrete panels. Modeling details of structural components, contact conditions between steel and concrete, associated boundary conditions and constitutive relationships for the cyclic loading are explained. Later, the load versus displacement curves, peak load and ultimate strength values, hysteretic characteristics and deflection profiles are verified with experimental data. The convergence of the numerical outcomes has been discussed to conclude the remarks.

Probabilistic Seismic Assessment of Base-Isolated NPPs Subjected to Strong Ground Motions of Tohoku Earthquake

AHMER ALI,NADIN ABU HAYAH,김두기,조성국 한국원자력학회 2014 Nuclear Engineering and Technology Vol.46 No.5

The probabilistic seismic performance of a standard Korean nuclear power plant (NPP) with an idealized isolationis investigated in the present work. A probabilistic seismic hazard analysis (PSHA) of the Wolsong site on the Koreanpeninsula is performed by considering peak ground acceleration (PGA) as an earthquake intensity measure. A procedure isreported on the categorization and selection of two sets of ground motions of the Tohoku earthquake, i.e. long-period andcommon as Set A and Set B respectively, for the nonlinear time history response analysis of the base-isolated NPP. Limitstate values as multiples of the displacement responses of the NPP base isolation are considered for the fragility estimation. The seismic risk of the NPP is further assessed by incorporation of the rate of frequency exceedance and conditional failureprobability curves. Furthermore, this framework attempts to show the unacceptable performance of the isolated NPP interms of the probabilistic distribution and annual probability of limit states. The comparative results for long and commonground motions are discussed to contribute to the future safety of nuclear facilities against drastic events like Tohoku.

Knowledge Discovery using Text Mining: A Programmable Implementation on Information Extraction and Categorization

Atika Mustafa,Ali Akbar,Ahmer Sultan 보안공학연구지원센터 2009 International Journal of Multimedia and Ubiquitous Vol.4 No.2

Textual data in electronic documents today around the world have no doubt brought forward all the information one could need and as data banks build up worldwide, and access gets easier through technology, it has become easier to overlook vital facts and figures that could bring about groundbreaking discoveries. This research paper discusses in detail an implementation of Information Extraction and Categorization in the text mining application that we have implemented. To extract terms from the document we have used modified version of Porter’s Algorithm for inflectional stemming. For calculating term frequencies for categorization, we have used a domain dictionary for ‘Computer Science’ domain.

Entropy generation in hydrodynamic slip flow over a vertical plate with convective boundary

Adnan Saeed Butt,Sufian Munawar,Asif Ali,Ahmer Mehmood 대한기계학회 2012 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.26 No.9

The present article aims to report the effects of hydrodynamic slip on entropy generation in the boundary layer flow over a vertical surface with convective boundary condition. Suitable similarity transformations are used to transform the fundamental equations of hydrodynamic and thermal boundary layer flow into ordinary differential equations. The governing equations are then solved numerically using the shooting method and the velocity and the temperature profiles are obtained for various values of parameters involved in the governing equations. The expressions for the entropy generation number and the Bejan number are presented and the results are discussed graphically and quantitatively for the slip parameter, the local Grashof number, the Prandtl number, the local convective heat transfer parameter, the group parameter and the local Reynolds number. It is observed that due to the presence of slip, entropy production in a thermal system can be controlled and reduced.

SC 합성 바닥판의 동적 거동

Sandeep Chaudhary, Kashyap Arvindbhai Patel, 김두기(Dookie Kim),조성국(Sung Gook Cho),Ahmer Ali 한국구조물진단유지관리학회 2011 한국구조물진단학회 학술발표회논문집 Vol.15 No.1

Studies are presented for the dynamic behaviour of steel-concrete composite floors. A typical two spans composite floor is considered for this study and assumed to be subjected to a typical earthquake. The deflection and stresses are obtained at different time instants for the composite floor with rigid connection and flexible connection. The FE model developed, in ABAQUS, for the study accounts for the nonlinear material behaviour. The flexibility of shear connectors between steel girder and concrete slab is found to significantly affect the dynamic behaviour of steel-concrete composite floors.

SC 합성 바닥판의 동적 거동

( Sandeep Chaudhary ),( Kashyap A. Patel ),김두기 ( Dookie Kim ),조성국 ( Sung Gook Cho ),( Ahmer Ali ) 한국구조물진단유지관리공학회 2011 한국구조물진단유지관리공학회 학술발표대회 논문집 Vol.15 No.1