• Earthquakes and Structures
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• v.24 no.4
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• pp.289-301
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• 2023

Developing a competent soil-bridge interaction model for the seismic analysis of piled foundation bridges is of utmost importance for investigating the seismic response and assessing fragility of these lifeline structures. To this end, ground motion histories are deemed necessary at various depths along the piles supporting the bridge. This may be effectively accomplished through time history analysis of a free-field standalone soil column extending from bedrock level to ground surface subjected to an input bedrock motion at its base. A one-dimensional site/ground response analysis (vide one-directional shear wave propagation through the soil column) is hence conducted in the present research accounting for the nonlinear hysteretic behavior of the soil stratum encompassing the bridge piled foundation. Two homogeneous soil profiles atop of bedrock have been considered for comparison purposes, namely, loose and dense sand. Analysis of the standalone soil column has been performed under a set of ten selected actual bedrock ground motions adopting a nonlinear time domain approach in an incremental dynamic analysis framework. Amplified retrieved PGA and maximum soil shear strains have been generally observed at various depths of the soil column when moving away from bedrock towards ground surface especially at large hazards associated with high (input) PGA values assigned at bedrock. This has been accompanied, however, by some attenuation of the amplified PGA values at shallower depths and at ground surface especially for the loose sand soil and particularly for cases with higher seismic hazards associated with large scaling factors of bedrock records.

• Earthquakes and Structures
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• v.18 no.5
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• pp.527-542
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• 2020

In traditional eccentrically braced steel frames, damages and plastic deformations are limited to the links and the main structure members are required tremendous sizes to ensure elasticity with no damage based on the force-based seismic design method, this limits the practical application of the structure. The high strength steel frames with eccentric braces refer to Q345 (the nominal yield strength is 345 MPa) steel used for links, and Q460 steel utilized for columns and beams in the eccentrically brace steel frames, the application of high strength steels not only brings out better economy and higher strength, but also wider application prospects in seismic fortification zone. Here, the structures with four type eccentric braces are chosen, including K-type, Y-type, D-type and V-type. These four types EBFs have various performances, such as stiffness, bearing capacity, ductility and failure mode. To evaluate the seismic behavior of the high strength steel frames with variable eccentric braces within the similar performance objectives, four types EBFs with 4-storey, 8-storey, 12-storey and 16-storey were designed by performance-based seismic design method. The nonlinear static behavior by pushover analysis and dynamic performance by time history analysis in the SAP2000 software was applied. A total of 11 ground motion records are adopted in the time history analysis. Ground motions representing three seismic hazards: first, elastic behavior in low earthquake hazard level for immediate occupancy, second, inelastic behavior of links in moderate earthquake hazard level for rapid repair, and third, inelastic behavior of the whole structure in very high earthquake hazard level for collapse prevention. The analyses results indicated that all structures have similar failure mode and seismic performance.

• Journal of the Korean Geophysical Society
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• v.8 no.4
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• pp.207-209
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• 2005

The local magnitude scales yield in the Southern Korean Peninsula following the Richter's original definition are reviewed. In order to compare the previous ML scales, the new distance correction term of ML scale is derived as - log A 0 = 1.017 log ( r/17) + 0.00028 ( r-17)2 + 2 .0 using broadband velocity seismograms from 126 local events occured from 2000 to 2004. The attenuation rate of this formula fall between those of western and eastern North America. This result is in nearly accord with the ML scales proposed by Kim and Park(2002). The differences between various ML scales is owing to insufficient seismic data not to distribute whole area of Southern Korea.

• Journal of the Earthquake Engineering Society of Korea
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• v.23 no.6
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• pp.301-309
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• 2019

A methodology to assess seismic fragility of a nuclear power plant (NPP) using a conditional mean spectrum is proposed as an alternative to using a uniform hazard response spectrum. Rather than the single-scenario conditional mean spectrum, which is the conventional conditional mean spectrum based on a single scenario, a multi-scenario conditional mean spectrum is proposed for the case in which no single scenario is dominant. The multi-scenario conditional mean spectrum is defined as the weighted average of different conditional mean spectra, each one of which corresponds to an individual scenario. The weighting factors for scenarios are obtained from a deaggregation of seismic hazards. As a validation example, a seismic fragility assessment of an NPP containment structure is performed using a uniform hazard response spectrum and different single-scenario conditional mean spectra and multi-scenario conditional mean spectra. In the example, the number of scenarios primarily influences the median capacity of the evaluated structure. Meanwhile, the control frequency, a key parameter of a conditional mean spectrum, plays an important role in reducing logarithmic standard deviation of the corresponding fragility curves and corresponding high confidence of low probability of failure (HCLPF) capacity.

• Advances in environmental research
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• v.5 no.2
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• pp.95-108
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• 2016

Urban geology is the study of urban geologic environments to provide a scientific basis for rational land use planning and urban development and provides information on geologic environments as a basis for city planners. Based on AEG recommendations, urban geological studies covered the urbanism and historical backgrounds, geological setting, engineering geological constraints and environmental assessments of understudied cities. The aim of this study is to provide a good view of urban geology of Tabriz city the capital of East Azerbaijan province in Iran. The topics of discussions about Tabriz city urban geology are included geologic (geomorphology, geology, climatology and hydrogeology), engineering geological (earthquake, landslide and geotechnical hazards investigations) and environmental characteristics (air, soil and water hazards assessment).The results of the urban geologic studies indicated that Tabriz city in terms of engineering geological and environmental constraints is at high risk potential and in terms of seismic activity and landslide instability is highly potential. In terms of air, soil and water pollution there are many important environmental concern in this city.

• Journal of the Korea Institute of Building Construction
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• v.23 no.4
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• pp.405-416
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• 2023

Recent seismic activities in countries like China and Turkey have underscored the widespread and severe damages that earthquakes can inflict globally. Being situated in a seismically active zone, South Korea can no longer regard itself as immune to earthquake hazards, necessitating the urgent adoption of proactive measures against such threats. The government has been proactive in evaluating, formulating processes, and methods for the seismic retrofitting of public buildings lacking in earthquake resistance. However, enforcement mechanisms for privately-owned apartment complexes are absent, and in the face of insufficient previous research and guidelines, preemptive measures for public safety remain alarmingly inadequate. With over 48% of residential structures in Korea aged over 30 years, and apartment complexes constituting more than 80% of these, the gravity of the situation is undeniable. This study deduces key factors for seismic retrofitting of apartment buildings like earthquake zones, soil type, building significance, aging degree, vulnerability, etc., based on building seismic design codes. It further proposes an algorithm for a more succinct and efficient determination of the priority of seismic reinforcements for apartment buildings.

• Journal of Korean Association for Spatial Structures
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• v.20 no.1
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• pp.79-86
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• 2020

The performance enhancement of various damping systems from natural hazards has become an highly important issue in engineering field. In this paper, ENTA hysteretic dampers were tested under cyclic loadings to evaluate their performance in terms of ductility and energy dissipation. The test results showed that the hysteretic dampers are effective damping systems to enhance the buildings performance for remodeling and retrofit of buildings. Also, the hysteretic dampers were modeled in FEM(Finite Element Method) structural analysis program. As comparing the computer modeling and the experiment, this study model reflects the nonlinear behavior of steel and derives the hysteresis loop.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2001.09a
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• pp.276-283
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• 2001

Performance-based design concepts require the next generation of codes. To implement the main concepts several design methodologies have been proposed. This paper reviews the framework of Korea Seismic Code and shows necessary modification for adoption of appropriate design methods. The selection of design earthquake levels with the introduction of risk factor is discussed for proper risk levels for all earthquake hazards. Displacement-based design, energy-based design, comprehensive design, and force-strength design methods are reviewed as one of possible next generation design methods. This paper proposes the direction of reconstruction for design earthquake levels with performance matrix, introduction of new design methods, and emphasis on non- structural components.

• Structural Engineering and Mechanics
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• v.14 no.2
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• pp.237-243
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• 2002

It is well known that torsionally unbalanced buildings are more vulnerable to earthquake hazards than are the regular structural systems. In this paper, a parametric investigation is presented, in order to observe the amplification in the internal forces, when increased eccentricities are used instead of the ones corresponding to the 5% accidental eccentricity. A series of five, ten-story framed and walled structures, with rather high torsional irregularity coefficients, are selected and a numerical test procedure is applied. Numerical results show that the maximum amplification in the internal forces at the most critical beams and columns at the flexible sides of the structures is about 10%. It is concluded that, more serious measures in the codes are needed in the case of this rather dangerous type of irregularity.

• Journal of the Korean GEO-environmental Society
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• v.15 no.9
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• pp.29-36
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• 2014

Under the situation that the seismic vulnerability are a worsening problem in many world's megacities, the disaster preparedness including earthquake hazards is a matter of primary concern in the capital city of Korea, Seoul. Especially, because it is hard to move or dismantle the architectural heritages, the mitigation of earthquake damages is potentially more difficult than other structures. Moreover, in order to decide the proper preparedness plan against future earthquakes, it is very important to understand how soils pass the seismic waves to architectural heritages. In this paper, therefore, the ground condition and depth of bedrock was investigated by the MASW-method at heritages located in Seoul. Then one-dimensional seismic response analysis was conducted based on the distribution of shear wave velocity. As the major result of analyses, peak acceleration, site amplification factor and natural period are proposed in each site for recurrence period.