• 수산해양기술연구
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• 제36권4호
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• pp.337-346
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• 2000

Earthquake is a natural disaster accompanied by damage of human and properties caused by the ground motion, crustal movements, faults as well as tidal wave. The earthquake is known to occur mostly in earthquake-prone areas and the Korean Peninsula is known to be relatively safe in terms of geological characteristics. In order to withstand on severe environmental dynamic random load such as an earthquake, the large structure need to be designed to withstand the anticipated seismic tremor. The seismetic design is essential for building structures, bridges, and large structures which is handles explosive gases. Thus, the necessity of earthquake resistant analysis for large structure is growing and the capability of dynamic analysis should be obtained. In this thesis, dynamic responses of a high building(height 60m, width 18) which subjected to random earthquake load are presented which responses are derived using dynamic analysis methods such as response spectrum analysis, mode superposition and direct integration. Each results are also compared to review the merit of each methods.

• Geomechanics and Engineering
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• 제21권2호
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• pp.143-152
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• 2020

Korean society experienced successive earthquakes exceeding 5.0 magnitude in the past three years resulting in an increasing concern about earthquake stability of urban infrastructures. This study focuses on the significant aspects of earthquake risk assessment for the cut-and-cover underground railway station based on two-dimensional dynamic numerical analysis. Presented are features from a case study performed for the railway station in Seoul, South Korea. The PLAXIS2D was employed for numerical simulation and input of the earthquake ground motion was chosen from Pohang earthquake records (M5.4). The paper shows key aspects of earthquake risk for soil-structure system varying important parameters including embedded depth, supported ground information, and applied seismicity level, and then draws several meaningful conclusions from the analysis results such as seismic risk assessment.

• Earthquakes and Structures
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• 제5권6호
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• pp.657-678
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• 2013

For economical earthquake resistant design of cable-stayed bridge tower, the use of energy dissipation systems for the earthquake protection of steel structures represents an alternative seismic design method where the tower structure could be constructed to dissipate a large amount of earthquake input energy through inelastic deformations in certain positions, which could be easily retrofitted after damage. The design of energy dissipation systems for bridges could be achieved as the result of two conflicting requirements: no damage under serviceability limit state load condition and maximum dissipation under ultimate limit state load condition. A new concept for cable-stayed bridge tower seismic design that incorporates sacrificial link scheme of low yield point steel horizontal beam is introduced to enable the tower frame structure to remain elastic under large seismic excitation. A nonlinear dynamic analysis for the tower model with the proposed energy dissipation systems is carried out and compared to the response obtained for the tower with its original configuration. The improvement in seismic performance of the tower with supplemental passive energy dissipation system has been measured in terms of the reduction achieved in different response quantities. Obtained results show that the proposed energy dissipation system of low yield point steel seismic link could strongly enhance the seismic performance of the tower structure where the tower and the overall bridge demands are significantly reduced. Low yield point steel seismic link effectively reduces the damage of main structural members under earthquake loading as seismic link yield level decreases due their exceptional behavior as well as its ability to undergo early plastic deformations achieving the concentration of inelastic deformation at tower horizontal beam.

• 한국지진공학회논문집
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• 제9권5호
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• pp.53-61
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• 2005

부재의 내력비, 강성비에 영향을 받는 다층 강구조 골조의 내진성능을 평가하기 위하여 내력비 및 강성비를 설계 파라메타로 하여 동적 비탄성 응답해석을 수행하였다. 해석 결과에 대한 분석을 통하여 내력비와 강성비의 변화폭이 큰 다층골조의 손상분포 예측식을 제안하였다. 본 연구에서 얻어진 결과는 다음과 같이 요약할 수 있다. 1) 보기둥 내력비 및 강성비가 작아질수록 1층의 기둥 주각부에서의 손상집중 현상이 크게 나타났다. 2) 보기둥 내력비 및 강성비를 고려하여 보붕괴형 강구조 다층골조의 손상분포를 예측할 수 있는 식을 제안하였으며, 예측식은 응답해석 결과와 좋은 대응을 보였다. 3) 본 연구에서 제안한 손상분포 예측식은 강접 및 반강접 보붕괴형 강구조 다층골조의 손상분포를 예측할 수 있을 것으로 판단된다.

• Earthquakes and Structures
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• 제10권5호
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• pp.1013-1032
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• 2016

Several historical earthquakes demonstrated that local amplification and soil nonlinearity are responsible for the uneven damage pattern of the structures and lifelines. On April $25^{th}$ 2015 the Mw7.8 Gorkha earthquake stroke Nepal and neighboring countries, and caused extensive damages throughout Kathmandu valley. In this paper, comparative studies between equivalent-linear and nonlinear seismic site response analyses in five affected strategic locations are performed in order to relate the soil behavior with the observed structural damage. The acceleration response spectra and soil amplification are compared in both approaches and found that the nonlinear analysis better represented the observed damage scenario. Higher values of peak ground acceleration (PGA) and higher spectral acceleration have characterized the intense damage in three study sites and the lower values have also shown agreement with less to insignificant damages in the other two sites. In equivalent linear analysis PGA varies between 0.29 to 0.47 g, meanwhile in case of nonlinear analysis it ranges from 0.17 to 0.46 g. It is verified from both analyses that the PGA map provided by the USGS for the southern part of Kathmandu valley is not properly representative, in contrary of the northern part. Similarly, the peak spectral amplification in case of equivalent linear analysis is estimated to be varying between 2.3 to 3.8, however in case of nonlinear analysis, the variation is observed in between 8.9 to 18.2. Both the equivalent linear and nonlinear analysis have depicted the soil fundamental period as 0.4 and 0.5 sec for the studied locations and subsequent analysis for seismic demands are correlated.

• Earthquakes and Structures
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• 제12권1호
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• pp.1-12
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• 2017

Historical earthquakes have shown that successive seismic events may occur in regions of high seismicity. Such a sequence of earthquakes has the potential to increase the damage level of the structures, since any rehabilitation between the successive ground motions is practically impossible due to lack of time. Few studies about this issue can be found in literature, most of which focused their attention on the seismic response of SDOF systems or planar frame structures. The aim of the present study is to examine the impact of seismic sequences on the damage level of 3D multistorey R/C buildings with various structural systems. For the purposes of the above investigation a comprehensive assessment is conducted using three double-symmetric and three asymmetric in plan medium-rise R/C buildings, which are designed on the basis of the current seismic codes. The buildings are analyzed by nonlinear time response analysis using 80 bidirectional seismic sequences. In order to account for the variable orientation of the seismic motion, the two horizontal accelerograms of each earthquake record are applied along horizontal orthogonal axes forming 12 different angles with the structural axes. The assessment of the results revealed that successive ground motions can lead to significant increase of the structural damage compared to the damage caused by the corresponding single seismic events. Furthermore, the incident angle can radically alter the successive earthquake phenomenon depending on the special characteristics of the structure, the number of the sequential earthquakes, as well as the distance of the record from the fault.

• Smart Structures and Systems
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• 제12권3_4호
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• pp.327-344
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• 2013

Beam string structure (BSS) is introduced as a new type of hybrid prestressed string structures. The composition and mechanics features of BSS are discussed. The main principles of wavelet packet transform (WPT), principal component analysis (PCA) and support vector machine (SVM) have been reviewed. WPT is applied to the structural response signals, and feature vectors are obtained by feature extraction and PCA. The feature vectors are used for training and classification as the inputs of the support vector machine. The method is used to a single one-way arched beam string structure for damage detection. The cable prestress loss and web members damage experiment for a beam string structure is carried through. Different prestressing forces are applied on the cable to simulate cable prestress loss, the prestressing forces are calculated by the frequencies which are solved by Fourier transform or wavelet transform under impulse excitation. Test results verify this method is accurate and convenient. The damage cases of web members on the beam are tested to validate the efficiency of the method presented in this study. Wavelet packet decomposition is applied to the structural response signals under ambient vibration, feature vectors are obtained by feature extraction method. The feature vectors are used for training and classification as the inputs of the support vector machine. The structural damage position and degree can be identified and classified, and the test result is highly accurate especially combined with principle component analysis.

• Earthquakes and Structures
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• 제22권1호
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• pp.1-13
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• 2022

When a building suffers damages under moderate to severe loading condition, its physical properties such as damping and stiffness parameters will change. There are different practical methods besides various numerical procedures that have successfully detected a range of these changes. Almost all the previous proposed methods used to work with translational components of mode shapes, probably because extracting these components is more common in vibrational tests. This study set out to investigate the influence of using both rotational and translational components of mode shapes, in detecting damages in 3-D steel structures elements. Three different sets of measured components of mode shapes are examined: translational, rotational, and also rotational/translational components in all joints. In order to validate our assumptions two different steel frames with three damage scenarios are considered. An iterative model updating program is developed in the MATLAB software that uses the OpenSees as its finite element analysis engine. Extensive analysis shows that employing rotational components results in more precise prediction of damage location and its intensity. Since measuring rotational components of mode shapes still is not very convenient, modal dynamic expansion technique is applied to generate rotational components from measured translational ones. The findings indicated that the developed model updating program is really efficient in damage detection even with generated data and considering noise effects. Moreover, methods which use rotational components of mode shapes can predict damage's location and its intensity more precisely than the ones which only work with translational data.

• 한국지진공학회논문집
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• 제22권3호
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• pp.193-199
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• 2018

This study aims to create a disaster management system after an earthquake. Japan's earthquake disaster management system, including the Disaster Countermeasures Basic Act, addresses all of the disaster phases of prevention, mitigation, preparedness and emergency response as well as recovery and reconstruction with roles and responsibilities among the national and local governments clearly defined. Korea's earthquake disaster management system are including the Disaster Countermeasures Basic, but when the 9.12 earthquake occurred, problems such as insufficient early response, study on the earthquake lack were revealed. This study conducted a field survey and analyzed coping process after Po Hang earthquake. Therefore, this study have found that Disaster Management Headquarters are operated rapidly. They are coped with urgent safety inspection for damage facilities and soil liquefaction with advanced equipment. And The headquarters interviewed with victims. So they found out What the victims needed. However, when carrying out relief activities, Research of temporary housing and allocation of donations was not rapid. Further, this study have found that earthquake specialists were lack and disaster information transfer was not working. This study will be utilized as fundamental data in planning disaster management system after an earthquake.

• Journal of Information Processing Systems
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• 제17권1호
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• pp.14-27
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• 2021

Strong earthquakes have caused substantial losses in recent years, and earthquake risk prevention has aroused a significant amount of attention. Earthquake risk prevention products can help improve the self and mutual-rescue abilities of people, and can create convenient conditions for earthquake relief and reconstruction work. At present, it is difficult for earthquake risk prevention information systems to meet the information requirements of multiple scenarios, as they are highly specialized. Aiming at mitigating this shortcoming, this study investigates and analyzes four user roles (government users, public users, social force users, insurance market users), and summarizes their requirements for earthquake risk prevention products in the whole disaster chain, which comprises three scenarios (pre-quake preparedness, in-quake warning, and post-quake relief). A targeted recommendation rule base is then constructed based on the case analysis method. Considering the user's location, the earthquake magnitude, and the time that has passed since the earthquake occurred, a targeted recommendation model is built. Finally, an Android APP is implemented to realize the developed model. The APP can recommend multi-form earthquake risk prevention products to users according to their requirements under the three scenarios. Taking the 2019 Lushan earthquake as an example, the APP exhibits that the model can transfer real-time information to everyone to reduce the damage caused by an earthquake.