• 한국정보통신설비학회:학술대회논문집
• /
• 2008.08a
• /
• pp.277-280
• /
• 2008

Starting from 2005, as the new city paradigm, the term 'u-City' was created in Korea. U-City service, as defined in "u-City law", is a service that connects and intermediates among government, traffic, welfare, environment, disaster mitigation, etc., and their data based on ubiquitous city technology and infrastructure. According to the survey executed by local governments, the improvements in the standard of living of citizens have in turn increased the needs for anti-mitigation services. Such trend is bolstered with the recent disasters such as the conflagration of Korean Soong-rae Gate and the devastating earthquake of Sichuan province. This article describes a concept of the u-City disaster prevention service and looks into the activities and planning of u-City disaster prevention service of local governments. This paper also briefly looks into the law and policies to derive the needs of u-City disaster prevention service as well as the current technologies and u-City disaster prevention services of local governments. Ultimately, this paper offers the strategic direction of developing u-Disaster Prevention City.

• Structural Engineering and Mechanics
• /
• v.35 no.1
• /
• pp.99-117
• /
• 2010

Beam-column joints are the key structural elements, which dictate the behavior of structures subjected to earthquake loading. Though large experimental work has been conducted in the past, still various issues regarding the post-yield behavior, ductility and failure modes of the joints make it a highly important research topic. This paper presents experimental results obtained for eight beam-column joints of different sizes and configuration under cyclic loads along with the analytical evaluation of their response using a simple and effective analytical procedure based on nonlinear static pushover analysis. It is shown that even the simplified analysis can predict, to a good extent, the behavior of the joints by giving the important information on both strength and ductility of the joints and can even be used for prediction of failure modes. The results for four interior and four exterior joints are presented. One confined and one unconfined joint for each configuration were tested and analyzed. The experimental and analytical results are presented in the form of load-deflection. Analytical plots are compared with envelope of experimentally obtained hysteretic loops for the joints. The behavior of various joints under cyclic loads is carefully examined and presented. It is also shown that the procedure described can be effectively utilized to analytically gather the information on behavior of joints.

• SUVANNABHUMI
• /
• v.13 no.2
• /
• pp.167-186
• /
• 2021

The Grand Stupa is mentioned in historical text as 'Rajakudakan', which means a royal building with a multitiered superstructure. This Grand Stupa is the principal construction of Wat Chedi Luang, and marks the center of the Chiang Mai City Plan. This study argues that the Grand Stupa was built in 1391 during Phaya Saen Mueang Ma's reign, possibly inspired by the construction of Ku Phaya in Bagan. Thereafter, in 1545, the Grand Stupa's superstructure collapsed after the great earthquake, resulted in the irreparable damage since then. Therefore, a survey using a 3D laser scanner is conducted to collect the most precise data on the current condition of the Grand Stupa, yielding an assumption of its reconstruction. Other simultaneous stupas or those that show a close architectural relationship (e.g. stupas in Wat Chiang Man and Wat Lok Moli and the stupa of King Tilokaraj in Wat Chet Yot in Chiang Mai) are also employed as research frameworks for the reconstruction. As a result, the architectural research on the Grands Stupa, compared with simultaneous stupas, yields a fruitful argument that the pre-collapse superstructure form of the Grand Stupa marks the most architectural similarity to the stupa of Wat Chiang Man.

• Journal of the Korean earth science society
• /
• v.30 no.7
• /
• pp.810-823
• /
• 2009

One of the critical factors in accurate determination of earthquake source parameters, and in prediction of seismic hazards is the detailed information related to the site amplification characteristics. The site amplification characteristics of the broad-band seismic stations in Korea were estimated as a function of frequency in the range of 0.2 to 20 Hz. A total of 1275 seismograms recorded from 43 earthquakes observed from 2003 to 2008 in the southern Korean Peninsula were used. It was found that the site amplification ratios for 28 stations estimated from the inversion of the ground motion model were approximately concordant with those obtained from the horizontal-to-vertical (H/V) spectral ratio except for some stations. The spectral site amplification characteristics obtained in this study did not show any considerable spatial distribution. It revealed to be largely correlated with the degree of weathering rather than the basement rock type. Considering the spectral site amplification ratio, 28 broad-band stations were classified into four groups and the characteristics of each group were described in the text.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.44 no.4
• /
• pp.503-512
• /
• 2024

In the seismic design standard, input waves for different levels of seismic performance are proposed in the form of design response spectra. At the time of establishing these standards, measured records of significant earthquakes that occurred domestically, such as the 2016 Gyeongju earthquake and the 2017 Pohang earthquake, were not included. Additionally, for the ground response analysis, shear wave velocities representing ground amplification characteristics were derived from the results of standard penetration tests (N-values) and applied in empirical formulas. This approach may not adequately capture sufficient information about the characteristics of domestic ground properties. Therefore, in this study, seismic records from the Gyeongju and Pohang earthquakes were modified to adjust the bedrock standard design response spectra. Ground response analyses were conducted using shear wave velocity profiles obtained from borehole tests in the Sejong City area. The shape of the response spectrum and ground amplification coefficient obtained from the ground response analysis were then compared with those from existing studies and seismic design standard.

• Structural Engineering and Mechanics
• /
• v.63 no.1
• /
• pp.47-53
• /
• 2017

The fundamental goal of this study is to minimize the uncertainty of the median fragility curve and to assess the structural vulnerability under earthquake excitation. Bayesian Inference with Markov Chain Monte Carlo (MCMC) simulation has been presented for efficient collapse response assessment of the independent intake water tower. The intake tower is significantly used as a diversion type of the hydropower station for maintaining power plant, reservoir and spillway tunnel. Therefore, the seismic fragility assessment of the intake tower is a pivotal component for estimating total system risk of the reservoir. In this investigation, an asymmetrical independent slender reinforced concrete structure is considered. The Bayesian Inference method provides the flexibility to integrate the prior information of collapse response data with the numerical analysis results. The preliminary information of risk data can be obtained from various sources like experiments, existing studies, and simplified linear dynamic analysis or nonlinear static analysis. The conventional lognormal model is used for plotting the fragility curve using the data from time history simulation and nonlinear static pushover analysis respectively. The Bayesian Inference approach is applied for integrating the data from both analyses with the help of MCMC simulation. The method achieves meaningful improvement of uncertainty associated with the fragility curve, and provides significant statistical and computational efficiency.

• Journal of the Korean earth science society
• /
• v.23 no.1
• /
• pp.15-29
• /
• 2002

Bayesian inversion for gravity and resistivity data was performed to investigate the cavity structure appearing as a lava tunnel in Cheju Island, Korea. Dipole-dipole DC resistivity data were proposed for a prior information of gravity data and we applied the geostatistical techniques such as kriging and simulation algorithms to provide a prior model information and covariance matrix in data domain. The inverted resistivity section gave the indicator variogram modeling for each threshold and it provided spatial uncertainty to give a prior PDF by sequential indicator simulations. We also presented a more objective way to make data covariance matrix that reflects the state of the achieved field data by geostatistical technique, cross-validation. Then Gaussian approximation was adopted for the inference of characteristics of the marginal distributions of model parameters and Broyden update for simple calculation of sensitivity matrix and SVD was applied. Generally cavity investigation by geophysical exploration is difficult and success is hard to be achieved. However, this exotic multiple interpretations showed remarkable improvement and stability for interpretation when compared to data-fit alone results, and suggested the possibility of diverse application for Bayesian inversion in geophysical inverse problem.

• Earthquakes and Structures
• /
• v.9 no.5
• /
• pp.937-956
• /
• 2015

Seismic isolation systems decouple structures from ground motions to protect them from seismic events. Seismic isolation devices have been implemented in many full-scale buildings and bridges because of their simplicity, economic effectiveness, inherent stability, and reliability. It is well known that the most uncertain aspect for obtaining the accurate responses of an isolated structure from seismic events is the seismic loading itself. It is needed to know the seismic response distributions of the isolated structure resulting from the randomness of earthquakes when probabilistic designing or probabilistic evaluating an isolated structure. Earthquake time histories are useful and often an essential element for designing or evaluating isolated structures. However, it is very challenging to gather the design and evaluation information for an isolated structure from many seismic analyses. In order to evaluate the seismic performance of an isolated structure, numerous nonlinear dynamic analyses need to be performed, but this is impractical. In this paper, the concept of the stochastic response database (SRD) is defined to obtain the seismic response distributions of an isolated structure instantaneously, thereby significantly reducing the computational efforts. An equivalent model of the isolated structure is also developed to improve the applicability and practicality of the SRD. The effectiveness of the proposed methodology is numerically verified.

• Geophysics and Geophysical Exploration
• /
• v.26 no.4
• /
• pp.268-274
• /
• 2023

Finite source inversion is performed with a Green's function matrix and geodetic coseismic displacement. Conventionally, the Green's function matrix is constructed using the Okada model (Okada, 1985). However, for more realistic earthquake simulations, recent research has widely adopted the physics-based model, which can consider various material properties such as elasticity, viscoelasticity, and elastoplasticity. We used the physics-based software PyLith, which is suitable for earthquake modeling. However, the PyLith does not provide a mesh generator, which makes it difficult to perform finite source inversions that require numerous subfaults and observation points within the model. Therefore, in this study, we developed CPInterface (COMSOL-PyLith Interface) to improve the convenience of finite source inversion by combining the processes of creating a numerical model including sub-faults and observation points, simulating earthquake modeling, and constructing a Green's function matrix. CPInterface combines the grid generator of COMSOL with PyLith to generate the Green's function matrix automatically. CPInterface controls model and fault information with simple parameters. In addition, elastic subsurface anomalies and GPS observations can be placed flexibly in the model. CPInterface is expected to enhance the accessibility of physics-based finite source inversions by automatically generating the Green's function matrix.

• Journal of the Korean earth science society
• /
• v.35 no.1
• /
• pp.54-68
• /
• 2014

In order to analyze the land surface properties in Seoul and its surrounding metropolitan area, several indices and land surface temperature were calculated by the Landsat satellites (e.g., Landsat 5, Landsat 7, and Landsat 8). The Landsat data came from only in the fall season with Landsat 5 on October 21, 1985, Landsat 7 on September 29, 2003, and Landsat 8 on September 16, 2013. The land surface properties used are the indices that represented Soil Adjusted Vegetation Index (SAVI), Modified Normalized Difference Wetness Index (MNDWI), Normalized Difference Wetness Index (NDWI), Tasseled cap Brightness, Tasseled cap Greenness, Tasseled cap Wetness Index, Normalized Difference Vegetation Index (NDVI) and Normalized Difference Built-up Index (NDBI) and the land surface temperature of the area in and around Seoul. Most indices distinguish very well between urban, rural, mountain, building, river and road. In particular, most of the urbanization is represented in the new city (e.g., Ilsan) around Seoul. According to NDVI, NDBI and land surface temperature, urban expansion is displayed in the surrounding area of Seoul. The land surface temperature and surface elevation have a strong relationship with the distribution and structure of the vegetation/built-up indices such as NDVI and NDBI. While the NDVI is positively correlated with the land surface temperature and is also negatively correlated with the surface elevation, the NDBI have just the opposite correlations, respectively. The NDVI and NDBI index is closely associated with the characteristics of the metropolitan area. Landsat 8 and Landsat 5 have very strong correlations (more than -0.6) but Landsat 7 has a weak one (lower than -0.5).