• KSCE Journal of Civil and Environmental Engineering Research
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• v.41 no.1
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• pp.21-28
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• 2021

The main purpose of this study is to assess the safety of the fixed anchorages subjected to the seismic motion for an operating facilities in the actual power plant. Thus, the experimental study was conducted to investigate the load response in the event of an actual seismic to the anchorages of a nonstructural components. Since there are economic and spatial constraints to study nonstructural components that actually have various forms, alternative test specimens of steel frames with mass were built and the shaking table test was carried out. In order to evaluate the dynamic characteristics and seismic performance, the natural frequency of the target structure was identified through the shaking table test and then the load response characteristics of the anchorage were evaluated by generating an artificial seismic effect like actual seismic. Finally, the structural stiffness was reinforced by fixing the steel frame to the test specimen using bolts, thereby reducing the load transmitted to the anchorage. It will be carried out on the reliability verification of the experiments and areas that have not been carried out due to the site conditions through the analytical approach in the future.

• Journal of Korean Association for Spatial Structures
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• v.20 no.2
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• pp.51-58
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• 2020

Recently, deep learning that is the most popular and effective class of machine learning algorithms is widely applied to various industrial areas. A number of research on various topics about structural engineering was performed by using artificial neural networks, such as structural design optimization, vibration control and system identification etc. When nonlinear semi-active structural control devices are applied to building structure, a lot of computational effort is required to predict dynamic structural responses of finite element method (FEM) model for development of control algorithm. To solve this problem, an artificial neural network model was developed in this study. Among various deep learning algorithms, a recurrent neural network (RNN) was used to make the time history response prediction model. An RNN can retain state from one iteration to the next by using its own output as input for the next step. An eleven-story building structure with semi-active tuned mass damper (TMD) was used as an example structure. The semi-active TMD was composed of magnetorheological damper. Five historical earthquakes and five artificial ground motions were used as ground excitations for training of an RNN model. Another artificial ground motion that was not used for training was used for verification of the developed RNN model. Parametric studies on various hyper-parameters including number of hidden layers, sequence length, number of LSTM cells, etc. After appropriate training iteration of the RNN model with proper hyper-parameters, the RNN model for prediction of seismic responses of the building structure with semi-active TMD was developed. The developed RNN model can effectively provide very accurate seismic responses compared to the FEM model.

• Journal of Korean Society of Steel Construction
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• v.14 no.6
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• pp.793-802
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• 2002

This study presented a finite element formulation for the dynamic analysis of horizontally curved I-girder bridges. The stiffness and mass matrices of the curved and the straight beam elements are formulated. Each node of both elements has seven degrees of freedom, including the warping degree of freedom. The curved beam element is derived from Kang and Yoo's theory of thin-walled curved beams. The computer program EQCVB has been developed to perform dynamic analyses of various horizontally curved I-girder bridges. The Gupta method is used to solve the eigenvalue problem efficiently, while the Wilson-${\theta}$ method is used for the seismic analysis. The efficiency of EQCVB is demonstrated by comparing solution time with ABAQUS. Using EQCVB, the study is applied to investigate the dynamic behavior of horizontally curved I-girder bridges under seismic loading.

• Journal of KSNVE
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• v.7 no.4
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• pp.655-661
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• 1997

Base-isolation of a primary structure generally decrete the seismic response of its own and the secondary structure. It may cause an adverse effect on the seismic response of secondary system when the system is submerged and subject to a considerable hydrodynamic effect. In this paper, it is shown how, and how much, the base isolation of the primary structure can affect the secondary system response in extreme cases through dynamic analysis of a simplified coupled model for a submerged secondary system and a base-isolated primary structure. As an aseismatic design approach to reduce the response of the submerged system, optimization of the fluid gap, which controls the hydrodynamic mass effect, is performed. As an alternative approach in case where the control of fluid gap is unrealistic, application of base isolation to the submerged system is suggested. Effectiveness of various combinations of the primary base and secondary base isolations are compared.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.17 no.1
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• pp.41-46
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• 2005

The seismic response characteristics of a port structure were investigated by the earthquake analyses of the structure subjected to high-, low-frequency component, and Uljin earthquakes. In the Fluid-Structure-Soil Interaction(FSSI) analysis, the fluid is modeled by the 4-node quadrilateral element which is a modification of a structural plane element, and the port structure and foundation is modelled by the plane strain element. Since the present method directly models the fluid-structure-soil interaction system using finite element method, it can be easily applied to the dynamic analysis of a 2-D fluid-port-soil system with complex geometry. The results of the seismic coefficient. added mass, and FSSI methods are compared. The results showed that the earthquake with high frequency components more affects the seismic response of the structure than that of low frequency components.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.10
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• pp.1265-1271
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• 2011

In this study, the safety of a rack structure was evaluated through seismic analysis considering fluid-structure interactions using a finite-element model. The rack structure was immersed under water, so it was influenced by the water. The fluid-structure interaction can be specified in terms of the hydrodynamic effect, which is defined as the added mass per unit length. Modal analysis and seismic analysis using the Floor Response Spectrum (FRS) were carried out under Operating Basis Earthquake (OBE) and Safe Shutdown Earthquake (SSE) conditions. The analytical maximum displacements of the rack structure were 0.29 and 0.36 mm under OBE and SSE conditions, respectively. The maximum stresses were 17.9 MPa under OBE conditions and 19.6 MPa under SSE conditions; these results corresponded to 23 % and 14% of the yield strength of the applied material, respectively.

• Coupled systems mechanics
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• v.6 no.3
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• pp.229-249
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• 2017

A new technique to mitigate irregular buildings with soil structure interaction (SSI) effect subjected to critical seismic waves is presented. The L-shape in plan irregular building for various reasons was selected, subjected to seismic a load which is a big problem for structural design especially without separation gap. The L-shape in plan building with different dimensions was chosen to study, with different rectangularity ratios and various soil kinds, to show the effect of the irregular building on the seismic response. A 3D building subjected to critical earthquake was analyzed by structural analysis program (SAP2000) fixed and with SSI (three types of soils were analyzed, soft, medium and hard soils) to find their effect on top displacement, base shear, and base torsion. The straining actions were appointed and the treatment of the effect of irregular shape under critical earthquake was made by using tuned mass damper (TMD) with different configurations with SSI and without. The study improve the success of using TMDs to mitigate the effect of critical earthquake on irregular building for both cases of study as fixed base and raft foundation (SSI) with different TMDs parameters and configurations. Torsion occurs when the L-shape in plan building subjected to earthquake which may be caused harmful damage. TMDs parameters which give the most effective efficiency in the earthquake duration must be defined, that will mitigate these effects. The parameters of TMDs were studied with structure for different rectangularity ratios and soil types, with different TMD configurations. Nonlinear time history analysis is carried out by SAP2000 with El Centro earthquake wave. The numerical results of the parametric study help in understanding the seismic behavior of L-shape in plan building with TMDs mitigation system.

• 한국지구물리탐사학회:학술대회논문집
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• 2008.10a
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• pp.185-190
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• 2008

Geophysical survey were investigated in the offshore around East Sea Research Institute, Korea Ocean Research and Development Institute (Jukbyeon-myun, Uljin-gu, Gyeongsangbuk-do, Korea). The surveys were conducted aboard the R/V Jangmok in 2008 using a hull-mounted EM 3002 multi-beam echosounder. Precise bathymetry and seabed images were obtained using multi-beam and thicknesses of sedimentary layer were found through seismic survey. Submarine topography deepens parallel to the coastline to -60 m and rock mass distributed in the southeast of study area. By finding the thickness of sedimentary layer through seismic survey, a sedimentary thickness on the study area was established. Futhermore, monitoring data of bathymetry, substructure and sedimentary environment will be secured through successive geophysical investigation.

• Journal of the Earthquake Engineering Society of Korea
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• v.23 no.3
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• pp.149-157
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• 2019

The purpose of this study is to investigate the effects of the significant duration of ground motions on responses of base-isolated nuclear power plants (NPPs). Two sets of ground motion records with short duration (SD) and long duration (LD) motions, scaled to match the target response spectrum, are used to perform time-history analyses. The reactor containment building in the Advanced Power Reactor 1400 (APR1400) NPP is numerically modeled using lumped-mass stick elements in SAP2000. Seismic responses of the base-isolated NPP are monitored in forms of lateral displacements, shear forces, floor response spectra of the containment building, and hysteretic energy of the lead rubber bearing (LRB). Fragility curves for different limit states, which are defined based on the shear deformation of the base isolator, are developed. The numerical results reveal that the average seismic responses of base-isolated NPP under SD and LD motion sets were shown to be mostly identical. For PGA larger than 0.4g, the mean deformation of LRB for LD motions was bigger than that for SD ones due to a higher hysteretic energy of LRB produced in LD shakings. Under LD motions, median parameters of fragility functions for three limit states were reduced by 12% to 15% compared to that due to SD motions. This clearly indicates that it is important to select ground motions with both SD and LD proportionally in the seismic evaluation of NPP structures.

• Economic and Environmental Geology
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• v.50 no.2
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• pp.129-143
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• 2017

The shallow sediments in the southwestern Ulleung Basin consist of mass flow deposits such as slide/slump and debris flow deposits (DFD), caused by slope failure. These sediments are proven to be important in studying geological disaster and stability of the seafloor. In this paper, we analysised the flow accumulation and slope failure susceptibility of the Ulleung Basin on the basis of multi-beam data, collected in this area. We also studied the distribution pattern and the seismic characteristics of the DFD in the uppermost layer of the Ulleung Basin on the basis of seismic data. The slope susceptibility was calculated as the frequency ratio of each factors including slope, aspect, curvature and stream power index (SPI), which causes the slope failure. These results indicate that the slope failure is frequently to occur in the southern and western continental slope of the Ulleung Basin. The sediment flow (mass flow) caused by the slope failure converges to the north and northwest of the Ulleung Basin. According to the seismic characteristics, the uppermost layer in study area can be divided into four sedimentary unit. These sedimentary units develop from the south and southwest to the north and northwest in association with slope susceptibility and flow accumulation.