• Journal of the Earthquake Engineering Society of Korea
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• v.5 no.2
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• pp.33-47
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• 2001

성능에 기초한 내진설계에서는 구조물이 보유하고 있는 능력을 효과적으로 파악하기 위해서 비선형 정적 해석이 적용되고 있다. 그러나 비선형 정적해석은 고차모드에 대한 효과를 고려하지 못함으로써 고층구조물이나 비정형 구조물과 같은 경우에는 정확한 비선형 지진응답의 산정과 내진성능을 평가하는데 문제점을 가지고 있다. 본 연구에서는 건축구조물의 선형 및 비선형 지진응답 평가를 위하여 응답 스펙트럼해석을 통하여 얻어지는 층전단력으로부터 층하중을 산정하는 유사동적해석법이 적용되었다. 제안된 방법을 비선형 정적 해석에 적용하여 구조물의 비선형 자동응답을 비선형 시간이력해석의 결과와 비교하였다. 기존의 층분포하중에 의한 비선형 지진응답과 비교하였으며, 제안된 방법에 의한 지진 응답이 구조물의 비선형 거동특성을 가장 정확하게 표현하였다. 그러므로 본 연구에서 제안된 방법을 사용하여 비선형 정적 해석을 수행한다면 비교적 명확한 건축물의 비선형 거동특성과 내진성능을 평가할 수 있을 것으로 판단된다.

• Journal of the Earthquake Engineering Society of Korea
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• v.20 no.7_spc
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• pp.545-551
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• 2016

This paper investigates seismic performance of a small-sized single story building in Korea. Nonlinear pushover anlaysis is performed to verify shear failure of RC short columns eventually led to performance degradation. Also, nonlinear time history analysis is performed using the same earthquakes from Gyeongju. Similar failure mode was obtained as in the report where a sudden rupture of the RC columns happened.

• Journal of Ocean Engineering and Technology
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• v.19 no.1 s.62
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• pp.26-32
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• 2005

Recent earthquakes, measuring over a magnitude of 5.0, on the eastern coast of Korea, have aroused interest in earthquake analyses and the seismic design of caisson-type breakwaters. Most earthquake analysis methods, such as equivalent static analysis, response spectrum analysis, nonlinear analysis, and capacity analysis, are deterministic and have been used for seismic design and performance evaluation of coastal structures. However, deterministic methods are difficult for reflecting on one of the most important characteristics of earthquakes, i.e. the uncertainty of earthquakes. This paper presents results of probabilistic seismic hazard assessment(PSHA) of an actual caisson-type breakwater, considering uncertainties of earthquake occurrences and soil properties. First, the seismic vulnerability of a structure and the seismic hazard of the site are evaluated, using earthquake sets and a seismic hazard map; then, the seismic risk of the structure is assessed.

• Structural Engineering and Mechanics
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• v.63 no.2
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• pp.259-268
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• 2017

In this paper, the incremental nonlinear dynamic analysis is used to evaluate the seismic performance of steel moment frame structures. To this purpose, three special moment frame structure with 5, 10 and 15 stories are designed according to the Iran's national building code for steel structures and the provisions for design of earthquake resistant buildings (2800 code). Incremental Nonlinear Analysis (IDA) is performed for 15 different ground motions, and responses of the structures are evaluated. For the immediate occupancy and the collapse prevention performance levels, the probability that seismic demand exceeds the seismic capacity of the structures is computed based on FEMA350. Also, fragility curves are plotted for three high-code damage levels using HASUS provisions. Based on the obtained results, it is evident that increase in the height of the frame structures reduces the reliability level. In addition, it is concluded that for the design earthquake the probability of exceeding average collapse prevention level is considerably larger than high and full collapse prevention levels.9.

• Journal of the Earthquake Engineering Society of Korea
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• v.18 no.4
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• pp.181-191
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• 2014

This research presents the nonlinear analysis model for reinforced concrete shear wall systems with special boundary elements as proposed by the Korean Building Code (KBC, 2009). In order to verify the analysis model, analytical results were compared with the experimental results obtained from previous studies. Established analytical model was used to perform nonlinear static and dynamic analyses. Analytical results showed that the semi-special shear wall improved significantly the performance in terms of ductility and energy dissipation as expected based on previous test results. Furthermore, nonlinear incremental dynamic analysis was performed using 20 ground motions. Based on computer analytical results, the ordinary shear wall, special shear wall and newly proposed semi-special shear wall systems were evaluated based on the methods in FEMA P965. The results based on the probabilistic approaches accounting for inherent uncertainties showed that the semi-special shear wall systems provide a high capacity/demand (ACMR) ratio owing to their details, which provide enough capacity to sustain large inelastic deformations.

• Journal of the Earthquake Engineering Society of Korea
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• v.26 no.1
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• pp.31-38
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• 2022

Based on the nonlinear static analysis and the approximate seismic evaluation method adopted in "Guidelines for seismic performance evaluation for existing buildings, two methods to calculate strength demand for retrofitting individual structural walls in unreinforced masonry buildings are proposed." The displacement coefficient method to determine displacement demand from nonlinear static analysis results is used for the inverse calculation of overall strength demand required to reduce the displacement demand to a target value meeting the performance objective of the unreinforced masonry building to retrofit. A preliminary seismic evaluation method to screen out vulnerable buildings, of which detailed evaluation is necessary, is utilized to calculate overall strength demand without structural analysis based on the difference between the seismic demand and capacity. A system modification factor is introduced to the preliminary seismic evaluation method to reduce the strength demand considering inelastic deformation. The overall strength demand is distributed to the structural walls to retrofit based on the wall stiffness, including the remaining walls or otherwise. Four detached residential houses are modeled and analyzed using the nonlinear static and preliminary evaluation procedures to examine the proposed method.

• Geomechanics and Engineering
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• v.20 no.4
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• pp.287-297
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• 2020

This paper investigates the stability of a three-dimensional (3D) wedge under the pseudo-static action of an earthquake based on the nonlinear Barton-Bandis (B-B) failure criterion. The influences of the mechanical parameters of the discontinuity surface, the geometric parameters of the wedge and the pseudo-static parameters of the earthquake on the stability of the wedge are analyzed, as well as the sensitivity of these parameters. Moreover, a stereographic projection is used to evaluate the influence of pseudo-static direction on instability mode. The parametric analyses show that the stability coefficient and the instability mode of the wedge depend on the mechanical parameter of the rock mass, the geometric form of the wedge and the pseudo-static state of the earthquake. The friction angle of the rock φ_b, the roughness coefficient of the structure surface JRC and the two angles related to strikes of the joints θ₁ and θ₂ are sensitive to stability. Furthermore, the sensitivity of wedge height h, the compressive strength of the rock at the fracture surface JCS and the slope angle α to the stability are insignificant.

• Journal of the Earthquake Engineering Society of Korea
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• v.21 no.6
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• pp.311-322
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• 2017

In this study, the seismic performance of concrete-steel composite moment frame structures equipped with seismic retrofitting systems such as seismic reinforcement, base isolators, and bracing members, which are typical earthquake damage mitigation systems, is evaluated through nonlinear dynamic analyses. A total of five frame models were designed and each frame model was developed for numerical analyses. A total of 80 ground acceleration data were used to perform the nonlinear dynamic analysis to measure ground shear force and roof displacement, and to evaluate the behavioral performance of each frame model by measuring inter-story drift ratios. The analysis results indicate that the retrofitting device of the base isolator make a significant contribution to generating relatively larger absolute displacement than other devices due to flexibility provided to interface between ground and column base. However, the occurrence of the inter-story drift ratio, which is a relative displacement that can detect the damage of the structure, is relatively small compared with other models. On the other hand, the seismic reinforced frame model enhanced with the steel plate at the lower part of the column was found to be the least efficient.

• Smart Structures and Systems
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• v.5 no.4
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• pp.495-505
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• 2009

Bridges form crucial links in the transportation network especially in high seismic risk regions. This research aims to provide a quantitative methodology for post-earthquake performance evaluation of the bridges. The experimental portion of the research involved shake table tests of a 4-span bridge which was subjected to progressively increasing amplitudes of seismic motions recorded from the Northridge earthquake. As part of this project, a high resolution long gauge fiber optic displacement sensor was developed for post-seismic evaluation of damage in the columns of the bridge. The nonlinear finite element model was developed using Opensees program to simulate the response of the bridge and the abutments to the seismic loads. The model was modified to predict the bent displacements of the bridge commensurate with the measured bent displacements obtained from experimental analysis results. Following seismic events, the tangential stiffness matrix of the whole structure is reduced due to reduction in structural strength. The nonlinear static push over analysis using current damaged stiffness matrix provides the longitudinal and transverse ultimate capacities of the bridge. Capacity loss in the transverse and longitudinal directions following the seismic events was correlated to the maximum displacements of the deck recorded during the events.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.20 no.5
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• pp.623-628
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• 2007

The accurate peak response estimation of a seismically excited structure with frictional damping system(FDS) is very difficult since the structure with FDS shows nonlinear behavior dependent on the structural period, loading characteristics, and relative magnitude between the frictional force and the excitation load. Previous studies have estimated that by replacing a nonlinear system with an equivalent linear one or by employing the response spectrum obtained based on nonlinear time history and statistical analysis. In the case that an earthquake load is defined with probabilistic characteristics, the corresponding response of the structure with FDS has probabilistic distribution. In this study, nonlinear time history analyses were performed for the structure with FDS subjected to artificial earthquake loads generated using Kanai-Tajimi filter. An equation for the probability density function (PDF) of the displacement response is proposed by adapting the PDF of the normal distribution. Finally, coefficients of the proposed PDF are obtained by regression analysis of the statistical distribution of the time history responses. Finally the correlation between PDFs and statistical response distribution is presented.