• Earthquakes and Structures
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• v.17 no.1
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• pp.91-99
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• 2019

Fragility analysis is an effective tool that is frequently used for seismic risk assessment of bridges. There are three different approaches to derive a fragility curve: experimental, empirical and analytical. Both experimental and empirical methods to derive fragility curve are based on past earthquake reports and expert opinions which are not suitable for all bridges. Therefore, analytical fragility analysis becomes important. Nonlinear time history analysis is commonly used which is the most reliable method for determining probabilistic demand models. In this study, to determine the probabilistic demand models of bridges, time history analyses were performed considering both material and geometrical nonlinearities. Serviceability limit states for three different service velocities were considered as a performance goal. Also, support displacements, component yielding and collapse limits were taken into account. Both serviceability and component fragility were derived by using maximum likely hood methods. Finally, the seismic performance and critical members of the bridge were probabilistically determined and clearly presented.

• Journal of the Korean Society of Safety
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• v.28 no.5
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• pp.49-53
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• 2013

This paper describes the assessment of seismic performance of the concrete gravity dam seismically reinforced by post-tensioned anchors. In order to evaluate the seismic performance, the response spectrum analyses have been carried out for 7 different configurations of the post-tensioned anchors, and then their performance improvement in the maximum tensile and compressive stresses is compared to each other. The comparative results demonstrate that the layout of the post-tensioned anchors strongly influences the seismic performance of the concrete gravity dam. In this study, the slightly-inclined vertical anchorage system shows the largest improvement on the overall performance of the seismically-excited concrete gravity dam.

• Journal of the Earthquake Engineering Society of Korea
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• v.17 no.2
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• pp.89-95
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• 2013

Structures in a nuclear power system are designed to be elastic even under an earthquake excitation. However a structural component such as an isolator shows inelastic behavior inherently. For the seismic assessment of nonlinear structures, response history analysis should be performed. In this study, the response of base isolation system was analyzed by response history analysis for the seismic performance assessment. Firstly, several seismic assessment criteria for a nuclear power plant structure were reviewed for the nonlinear response history analysis. Based on these criteria, the spectrum matched ground motion generation method modifying a seed earthquake ground motion time history was adjusted. Using these spectrum matched accelerograms, the distribution of displacement responses of the simplified base isolation system was evaluated. The resulting seismic responses excited by the modified ground motion time histories and the synthesized time history generated by stochastic approach were compared. And the response analysis of the base isolation system considering the different intensities in each orthogonal direction was performed.

• Earthquakes and Structures
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• v.22 no.5
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• pp.487-502
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• 2022

China is prone to earthquake disasters, and the higher seismic performance is required by many existing civil buildings. And seismic evaluation and retrofit are effective measures to mitigate seismic hazards. With the development of performance-based seismic design and diverse retrofit technology for buildings, advanced evaluation methods and retrofit strategies are in need. In this paper, we introduced the evolution of seismic performance objectives in China combined with performance-based seismic design. Accordingly, multi-phase evaluation methods and comprehensive seismic capacity assessment are introduced. For buildings with seismic deficiency or higher performance requirements, the retrofit technologies are categorized into three types: component strengthening, system optimization, and passive control. Both engineering property and social property for the retrofit methods are discussed. The traditional seismic retrofit methods usually are costly and disturbing, and for example in Beijing, seismic strengthening costs approx. 1000 RMB/m² (for 160 USD/m²), for hospital building even more expensive as 5000 RMB/m²(for 790 USD/m²). So cost-efficient and little disturbance methods are promising techniques. In the end, some opinions about the retrofit strategy and schemes category are shared and wish to discuss the situation and future of seismic retrofit in China.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.85-88
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• 2005

The purpose of this study is to assess the seismic performance of reinforced concrete bridge piers using inelastic finite element analysis. The accuracy and objectivity of the assessment process may be enhanced by the use of sophisticated nonlinear finite element analysis program. A computer program, named RCAHEST(Reinforced Concrete Analysis in Higher Evaluation System Technology), for the analysis of reinforced concrete structures was used. The proposed numerical method for the seismic performance assessment of reinforced concrete bridge piers is verified by comparison with the reliable experimental results.

• Journal of the Earthquake Engineering Society of Korea
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• v.28 no.4
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• pp.193-203
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• 2024

Existing reinforced concrete (RC) building frames constructed before the seismic design was applied have seismically deficient structural details, and buildings with such structural details show brittle behavior that is destroyed early due to low shear performance. Various reinforcement systems, such as fiber-reinforced polymer (FRP) jacketing systems, are being studied to reinforce the seismically deficient RC frames. Due to the step-by-step modeling and interpretation process, existing seismic performance assessment and reinforcement design of buildings consume an enormous amount of workforce and time. Various machine learning (ML) models were developed using input and output datasets for seismic loads and reinforcement details built through the finite element (FE) model developed in previous studies to overcome these shortcomings. To assess the performance of the seismic performance prediction models developed in this study, the mean squared error (MSE), R-square (R²), and residual of each model were compared. Overall, the applied ML was found to rapidly and effectively predict the seismic performance of buildings according to changes in load and reinforcement details without overfitting. In addition, the best-fit model for each seismic performance class was selected by analyzing the performance by class of the ML models.

• Journal of the Earthquake Engineering Society of Korea
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• v.9 no.5 s.45
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• pp.63-74
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• 2005

The purpose of this study is to assess the seismic performance of reinforced concrete bridge columns using inelastic finite element analysis. The accuracy and objectivity of the assessment process may be enhanced by the use of sophisticated nonlinear finite element analysis program. A computer program, named RCAHEST (Reinforced Concrete Analysis in Higher Evaluation System Technology), for the analysis of reinforced concrete structures was used. Damage index aims to provide a means of quantifying numerically the damage in reinforced concrete bridge columns sustained under earthquake loading. The proposed numerical method for the seismic performance assessment of reinforced concrete bridge columns is verified by comparison with reliable experimental results.

• Earthquakes and Structures
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• v.15 no.5
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• pp.487-498
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• 2018

Buckling-restrained braces are passive control devices with high level of energy dissipation ability. However, they suffer from low post-yield stiffness which makes them vulnerable to severe ground motions, especially near-field earthquakes. Among the several methods proposed to improve resistance of BRB frames, mega-brace configuration can be a solution to increase frame lateral strength and stiffness and improve distribution of forces to prevent large displacement in braces. Due to the limited number of research regarding the performance of such systems, the current paper aims to assess seismic performance of BRB frames with mega-bracing arrangement under near-field earthquakes via a detailed probabilistic framework. For this purpose, a group of multi-story mega-BRB frames were modelled by OpenSEES software platform. In the first part of the paper, simplified procedures including nonlinear pushover and Incremental Dynamic Analysis were conducted for performance evaluation. Two groups of near-fault seismic ground motions (Non-pulse and Pulse-like records) were considered for analyses to take into account the effects of record-to-record uncertainties, as well as forward directivity on the results. In the second part, seismic reliability analyses are conducted in the context of performance based earthquake engineering. Two widely-known EDP-based and IM-based probabilistic frameworks are employed to estimate collapse potential of the structures. Results show that all the structures can successfully tolerate near-field earthquakes with a high level of confidence level. Therefore, mega-bracing configuration can be an effective alternative to conventional BRB bracing to withstand near-field earthquakes.

• Journal of the Earthquake Engineering Society of Korea
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• v.10 no.3 s.49
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• pp.21-33
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• 2006

The purpose of this study is to assess the seismic performance of reinforced concrete bridge columns using nonlinear finite element analysis. The accuracy and objectivity of the assessment process may be enhanced by the use of sophisticated nonlinear finite element analysis program. A computer program, named RCAHEST (Reinforced Concrete Analysis in Higher Evaluation System Technology), for the analysis of reinforced concrete structures was used. Damage index aims to provide a means of quantifying numerically the damage in reinforced concrete bridge columns sustained under earthquake loading. The proposed numerical method for the seismic performance assessment of reinforced concrete bridge columns is verified by comparison with reliable experimental results.

• Structural Engineering and Mechanics
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• v.73 no.1
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• pp.53-64
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• 2020

In different high seismic regions around the world, many non-ductile existing reinforced concrete frame buildings, built without adequate seismic detailing requirements, have been damaged or collapsed after past earthquakes. The assessment and the retrofit of these non-ductile concrete structures is crucial theme of research for all the scientific community of engineers. In particular, a careful assessment of the existing building is fundamental for understanding the failure mechanisms that govern the collapse of the structure or the achievement of the recommended limit states. Based on the seismic assessment, the best retrofit strategy can be designed and applied to the structure. A school building located in Avellino province (Italy) is the case study. The analysis of seismic vulnerability carried out on the mentioned building has highlighted deficiencies in both static and seismic load conditions. The retrofit of the building has been designed based on different retrofit options in order to show the real retrofit design developed from the engineers to achieve the seismic safety of the building. The retrofit costs associated to structural operations are calculated for each case and have been summed up to the costs of the in situ tests. The paper shows a real retrofit design case study in which the best solution is chosen based on the results in terms of structural performance and cost among the different retrofit options.