• Journal of Institute of Control, Robotics and Systems
• /
• v.3 no.3
• /
• pp.219-226
• /
• 1997

지구를 원궤도로 돌고 있는 위성 운동과 지진에 흔들리는 건물 진동을 선형 확률적 미분 방정식으로 나타내고 최적화 제어를 위하여 리스크 센서티브 제어기를 사용한다. 리스크 센서티브 파라미터에 따라서 코스트 함수의 평균과 분산이 변하게 된다. 이 파라미터가 무한히 커지면 리스크 센서티브 제어기는 기존의 LQG 제어기와 같아지므로 리스크 샌서티브 제어이론은 LQG 제어 이론을 포함한 종합적인 이론이다. 이 논문에서는 리스크 센서티브 이론을 소개하고, 리스크 센서티브 제어 방식의 성능 측정및 평가 방법을 도출하기 위하여 공분산을 이용하면 리스크 센서티브 제어기는 기존의 LQG 제어기 보다 우수한 성능을 나타낸다는 것을 보여준다. 시뮬레이션을 통하여 위성의 자세및 궤도 운동 제어와 건물 진동 제어에 활용된 리스크 센서티브 제어기의 향상된 성능과 안정성을 보여준다.

• Journal of the Korean Association of Geographic Information Studies
• /
• v.19 no.4
• /
• pp.17-35
• /
• 2016

Earthquake-induced disasters are often more severe in locations with soft soils than firm soils or rocks due to differences in ground motion amplification. On a regional scale, such differences can be estimated by spatially predicting subsurface soil thickness over the entire target area. In general, soil deposits are generally deeper in coastal or riverside areas than in inland regions. In this study, a coastal metropolitan area, Incheon, was selected to assess site effects and provide information on seismic hazards. Spatial prediction of geotechnical layers was performed for the entire study area within the GIS framework. Approximately 7,000 existing borehole drilling data in the Incheon area were gathered and archived into the GIS Database (DB). In addition, surface geotechnical data were acquired from a walkover survey. Based on the built geotechnical DB, spatial zoning maps of site-specific seismic response parameters were created and presented for use in a regional seismic strategy. Site response parameters were performed to determine site coefficients for seismic design over the entire target area and compared with each other. Site classifications and subsequent seismic zoning were assigned based on site coefficients. From this seismic zonation case study in Incheon, we verified that geotechnical GIS-DB can create spatial zoning maps of site-specific seismic response parameters that are useful for seismic hazard mitigation particularly in coastal metropolitan areas.

• Journal of the Korean Geotechnical Society
• /
• v.25 no.1
• /
• pp.5-19
• /
• 2009

Most of earthquake-induced geotechnical hazards have been caused by the site effects relating to the amplification of ground motion, which is strongly influenced by the local geologic conditions such as soil thickness or bedrock depth and soil stiffness. In this study, an integrated GIS-based information system for geotechnical data, called geotechnical information system (GTIS), was constructed to establish a regional counterplan against earthquake-induced hazards at an urban area of Daejeon, which is represented as a hub of research and development in Korea. To build the GTIS for the area concerned, pre-existing geotechnical data collections were performed across the extended area including the study area and site visits were additionally carried out to acquire surface geo-knowledge data. For practical application of the GTIS used to estimate the site effects at the area concerned, seismic zoning map of the site period was created and presented as regional synthetic strategy for earthquake-induced hazards prediction. In addition, seismic zonation for site classification according to the spatial distribution of the site period was also performed to determine the site amplification coefficients for seismic design and seismic performance evaluation at any site in the study area. Based on this case study on seismic zonations in Daejeon, it was verified that the GIS-based GTIS was very useful for the regional prediction of seismic hazards and also the decision support for seismic hazard mitigation.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.12 no.3
• /
• pp.257-264
• /
• 2010

This study proposed the aseismic design concept for underground space based on site response analysis and laboratory tests. The results of this study showed that the location of the control points of input motions such as design response spectra and time history of acceleration and the assumption of bedrock properties such as elasticity or rigidity play an important role in aseismic design of underground space. Therefore, the appropriate ground response model among models applying motions such as free surface motion, bedrock motion, or bedrock outcropping motion must be utilized to provide reasonable boundary conditions of underground space under earthquake loading and practical aseismic design.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.11 no.5
• /
• pp.1805-1813
• /
• 2010

This paper presented regarding an parametric study to investigate seismic capacity evaluation of semi-rigid steel frame infilled with composit panel. In order to propose the optimum retrofit of the steel frame, we analysed the various pattern of retrofitted steel frame subjected to weak/medium earthquake. Steel frame with composit panel was analysed by Time history analyses analysis. The model were analysed using the suites of ground motion developed by NEHRP project on steel moment resisting frame. These earthquakes consist of 20 horizontal ground acceleration record each, i.e., a 10%, 50% probability of accidence in a 50 year period. We considered the semi-rigid connection which are commonly used in field, and modeled the nonlinear connection element (GAP) between panel and frame. It was shown that how is the steel frame with composit panel effected. We also examined the response of retrofitted frame.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.17 no.1
• /
• pp.284-289
• /
• 2016

In recent years, the earthquake sequence in Christchurch, New Zealand (NZ) was unprecedented in terms of repeated earthquake shocks with substantial levels of ground motion affecting modern infrastructure, and in particular, broad and precise reports for liquefaction-induced permanent ground deformation (PGD) and repairs of wastewater (WW) pipelines were collected. In this study, a geographical information system (GIS) and linear regression analysis were performed using data for the length and repair points of earthenware (EW) and concrete (CONC) wastewater pipelines acquired after the MW 6.2 February 22, 2011 earthquake. The repair rates (repairs/km) for the EW and CONC wastewater pipelines were evaluated inside the areas of PGD, and both angular distortion of ground and lateral ground strain were calculated from the high resolution LiDAR data acquired before and after the seismic event. The research results showed that both pipelines have similar trends of damage but the CONC wastewater pipeline with higher stiffness showed less damage. The results of linear regression analyses can be used to predict the repair rates for EW and CONC wastewater pipelines inside the areas of PGD induced by future earthquakes.

• Journal of the Korean GEO-environmental Society
• /
• v.24 no.2
• /
• pp.31-40
• /
• 2023

We installed temporary strong motion seismometers at the ground surface, 1 m, 2 m, and 9 m at an existing seismic station that houses permanent seismometers installed at 20 m and 100 m, to investigate the influence of installation depth on the recorded ambient and anthropogenic noise level and the characteristics of earthquake signals. Analysis of the ambient noise shows that anthropogenic noise dominates where vibration period T < 1 s at the studied site, whereas wind speed appears to be strongly correlated with the noise level at T > 1 s. Frequency-wavenumber analysis of 2D seismometer array suggests that ambient noise in short periods are predominantly body waves, rather than surface waves. The level of ambient noise was low at 9 m and 20 m, but strong amplification of noise level at T < 0.1 s was observed at the shallow seismometers. Both the active-source test result and the recorded earthquake data demonstrated that the signal level is decreased with the increase of depth. Our result also shows that recorded motions at the ground and 1 m are strongly amplified at 20 Hz (T = 0.05 s), likely due to the resonance of the 3 m thick soil layer. This study demonstrates that analysis of ambient and active-source vibration may help find optimal installation depth of strong motion seismometers. We expect that further research considering various noise environments and geological conditions will be helpful in establishing a guideline for optimal installation of strong motion seismometers.

• Korean Journal of Mineralogy and Petrology
• /
• v.35 no.4
• /
• pp.485-505
• /
• 2022

On November 15, 2017, a Mw 5.4 Pohang Earthquake occurred at about 4 km hypocenter in the Heunghae area, and caused great damage to Pohang city, Korea. In the Heunghae area, which is the central part of the Pohang Basin, the Cretaceous Gyeongsang Supergroup and the Late Cretaceous to Early Paleogene Bulguksa igneous rocks as basement rocks and the Neogene Yeonil Group as the fillings of the Pohang Basin, are distributed. In this paper, structural and geological researches on the crustal deformations (folds, faults, joints) in the Pohang Basin and the coseismic ground deformations (sand volcanoes, ground cracks, pup-up structures) of Pohang Earthquake were carried out, and the deformation history of the Pohang Basin and characteristics of the coseismic ground deformations were considered. The crustal deformations were formed through at least five deformation stages before the Quaternary faulting: forming stages of the normal-slip (Gokgang fault) faults which strike (N)NE and dip at high angles, and the high-angle joints of E-W trend regionally recognized in Yeonil Group and the faults (sub)parallel to them, and the conjugate normal-slip faults (Heunghae fault and Hyeongsan fault) which strike E-W and dip at middle or low angles and the accompanying E-W folds, and the conjugate strike-slip faults dipped at high angles in which the (N)NW and E-W (NE) striking fault sets show the (reverse) sinistral and dextral strike-slips, respectively, and the conjugate reverse-slip faults in which the NNE and NNW striking fault sets dip at middle angles and the accompanying N-S folds. Sand volcanoes often exhibit linear arrangements (sub)parallel to ground cracks in the coseismic ground deformations. The N-S or (N)NE trending pop-up structures and ground cracks and E-W or (W)NW trending ground were formed by the reverse-slip movement of the earthquake source fault and the accompanying buckling folding of its hanging wall due to the maximum horizontal stress of the Pohang Earthquake source. These structural activities occurred extensively in the Heunghae area, which is at the hanging wall of the earthquake source fault, and caused enormous property damages here.

• Journal of the Korean Society of Hazard Mitigation
• /
• v.7 no.5
• /
• pp.27-35
• /
• 2007

This study presents a non -prismatic beam element for modeling the elastic and inelastic behavior of the steel beam, which has the post-Northridge connections in steel moment frames that are subjected to earthquake ground motions. The elastic stiffness matrix for non-prismatic members with reduced beam section (RES) connection is in the closed-form. The plasticity model is of a discrete type and is composed of a series of nonlinear hinges connected by rigid links. The hardening rules can model the inelastic behavior for monotonic and random cyclic loading, and the effects of local buckling. Verification and calibration of the model are presented in a companion paper.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.13 no.5
• /
• pp.13-18
• /
• 1993

The purpose of this study is to analyze the seismic effects of Lead Rubber Bearing base isolators on bridges. Base isolation is the tool to minimize the effect of earthquake before the seismic force is transfered to the structure. Currently, many structures including the buildings, power plants, and bridges, were built and planned with base isolation method. The simple model is developed for bridges with Lead Rubber Bearings. Equations of motion are solved by Newmark ${\beta}$ method. Springs representing the base isolators are assumed as bilinear springs and piers are modeled as nonlinear springs implementing Q-HYST model. Analysis is performed for the selected bridge. El Centro (N-S) earthquake(1940) is used. Deck displacement, pier ductility and pier shear force are calculated for the various Lead Rubber Bearings.