• Journal of the Computational Structural Engineering Institute of Korea
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• v.36 no.2
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• pp.105-112
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• 2023

In this study, structural analyses were conducted to analyze the performance of a bridge to which friction pendulum systems (FPSs) were applied using different friction models. A Coulomb friction model and a rate dependent friction model were constructed using the friction coefficient of a PVDF/MgO friction material to analyze the effect of different friction analysis models. The Coulomb friction model uses a single friction coefficient regardless of friction velocity, while the rate dependent friction model can reflect the change in the friction coefficient with friction velocity. Nonlinear time history and seismic fragility analyses were conducted to confirm responses of the bridge. The seismic responses of a deck and a column were used to evaluate the performance of the base isolated bridge, and a friction model that can effectively evaluate the performance of isolated bridges was analyzed.

• Structural Engineering and Mechanics
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• v.69 no.6
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• pp.591-605
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• 2019

Investigations on seismic performance of eccentrically braced frames equipped with dual vertical links have received little attention. Therefore, the main goal of this paper is to describe design steps for such frames and evaluate nonlinear performance of this system according to the reliability analysis. In this study, four and eight story frame structures are analyzed and the response modification factors for different intensity and damage levels are derived in a matrix form based on a new approach. According to the obtained results, the system has high ductility and acceptable seismic performance. Moreover, it is concluded that using response modification factor equal to 8 in the design of system provides desirable seismic reliability under the design and maximum probable hazard levels. Due to desirable performance and significant advantages of the dual vertical links, this system can be used as a main lateral load bearing system, in addition to its application for rehabilitation of damaged structures.

• Journal of the Korean Society of Hazard Mitigation
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• v.4 no.1 s.12
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• pp.1-14
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• 2004

The objective of this study is firstly to frame up the seismic safety of concrete gravity dams. It is necessary to analyze seismic response and evaluate seismic performance of concrete gravity dams during earthquake. In this study, seismic damage and dynamic analysis of concrete gravity dams using structural analysis package such as SAP2000 and MIDAS were performed. Additional dynamic water pressure due to earthquake considered as additional mass for numerical seismic analysis. According detailed analysis, the vibration through the dam structure (transverse to water flow) seems to be very critical depending on the shape of the dam. For more precise evaluation of seismic fragility of concrete gravity dams, further research is still needed.

• Journal of the Earthquake Engineering Society of Korea
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• v.7 no.2
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• pp.93-102
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• 2003

A technique for the seismic reliability evaluation of electric power transmission network system(EPTS) was developed to evaluate reliability indices corresponding to the whole network system and to each node within. A network model with nodes and links for EPTS was established, and a seismic substation fragility curve obtained from seismic fragilities of power system facilities was derived. A point source model, the doubly truncated Gutenberg-Richter relationship, and earthquake intensity attenuation formula was applied to simulate seismic events. Using Monte-Carlo simulation method, the seismic reliability of EPTS was evaluated and, it appeared that seismic effect on EPTS of korea has to be considered.

• Journal of the Earthquake Engineering Society of Korea
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• v.15 no.3
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• pp.45-55
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• 2011

In this study, the state of the art and characteristics of major Korean port structures were investigated and analyzed. Damage of port structures during earthquakes, evaluation systems of seismic damage and seismic designs have also been investigated. Based on the research, a methodology of seismic damage estimation was proposed considering geotechnical information and the characteristics of the fragility of port structures.

• Smart Structures and Systems
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• v.2 no.4
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• pp.339-355
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• 2006

A procedure to retrofit existing essential facilities subjected to seismic excitation is proposed. The main features of this procedure are to reduce maximum acceleration and associated forces in buildings subjected to seismic excitation by reducing their strength (weakening). The weakening retrofit, which is an opposite strategy to strengthening, is particularly suitable for buildings having overstressed components and foundation supports or having weak brittle components. However, by weakening the structure large deformations are expected. Supplementaldamping devices however can control the deformations within desirable limits. The structure retrofitted with this strategy will have, therefore, a reduction in the acceleration response and a reduction in the deformations, depending on the amount of additional damping introduced in the structure. An illustration of the above strategy is presented here through an evaluation of the inelastic response of the structure through a nonlinear dynamic analysis. The results are compared with different retrofit techniques. A parametric analysis has also been carried out to evaluate the effectiveness of the retrofitting method using different combination of the performance thresholds in accelerations and displacements through fragility analysis.

• Earthquakes and Structures
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• v.1 no.2
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• pp.197-214
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• 2010

The paper presents a methodology for developing earthquake damage and loss scenarios for urban areas, as well as its application to two cities located in Mediterranean countries, Grevena (in Greece) and D$\ddot{u}$zce (in Turkey), that were struck by strong earthquakes in the recent past. After compiling the building inventory in each city, fragility curves were derived using a hybrid approach previously developed by the authors, and a series of seismic scenarios were derived based on microzonation studies that were specifically conducted for each city (see companion paper by Pitilakis et al.). The results obtained in terms of damage estimates, required restoration times and the associated costs are presented in a GIS environment. It is deemed that both the results obtained, and the overall methodology and tools developed, contribute towards the enhancement of seismic safety in the Mediterranean area (as well as other earthquake-prone regions), while they constitute a useful pre-earthquake decision-making tool for local authorities.

• Nuclear Engineering and Technology
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• v.53 no.7
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• pp.2396-2406
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• 2021

The Pacific Earthquake Engineering Research (PEER) Center has been developing a performance-based earthquake engineering (PBEE) methodology, which is based on explicit determination of performance, e.g., monetary losses, in a probabilistic manner where uncertainties in earthquake ground motion, structural response, damage estimation, and losses are explicitly considered. To carry out the PEER PBEE procedure for a component of the nuclear power plant (NPP) such as the cable tray system, hazard curve and spectra were defined for two hazard levels of the ground motions, namely, operation basis earthquake, and safe shutdown earthquake. Accordingly, two sets of spectral compatible ground motions were selected for dynamic analysis of the cable tray system. In general, the PBEE analysis of the cable tray in NPP was introduced where the resulting floor motions from the time history analysis (THA) of the NPP structure should be used as the input motion to the cable tray. However, for simplicity, a finite element model of the cable tray was developed for THA under the effect of the selected ground motions. Based on the structural analysis results, fragility curves were generated in terms of specific engineering demand parameters. Loss analysis was performed considering monetary losses corresponding to the predefined damage states. Then, overall losses were evaluated for different damage groups using the PEER PBEE methodology.

• Journal of the Earthquake Engineering Society of Korea
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• v.26 no.6
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• pp.255-265
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• 2022

In order to determine fragility curves, the limit state of piers for each damage level is suggested in this paper based on the previous test results in Korea, including our test results. In previous studies, the quantitative measures for damage levels of piers have been represented by curvature ductility, lateral drift ratio, or displacement ductility. These measures are transformed to lateral drift ratios of piers for consistency, and the transformed values are compared and verified with our push-over test results for flexural RC piers with a circular cross-section. The test specimens are categorized concerning the number of lap-splices in the plastic hinge region and whether seismic design codes are satisfied or not. Based on the collected test results in Korea, including ours, the lateral drift ratio for each pier damage level is suggested.

• Steel and Composite Structures
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• v.23 no.1
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• pp.95-105
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• 2017

The use of superelastic shape memory alloys (SMAs) as reinforcements in concrete structures is gradually gaining interest among researchers. Because of different mechanical properties of SMAs compared to the regular steel bars, the use of SMAs as reinforcement in the concrete may change the response of structures under seismic loads. In this study, the effect of SMAs as reinforcement in concrete structures is analytically investigated for 3-, 6- and 8-story reinforced concrete (RC) buildings. For each concrete building, three different reinforcement details are considered: (1) steel reinforcement (Steel) only, (2) SMA bar used in the plastic hinge region of the beams and steel bar in other regions (Steel-SMA), and (3), beams fully reinforced with SMA bar (SMA) and steel bar in other regions. For each case, columns are reinforced with steel bar. Incremental Dynamic Analyses (IDA) are performed using ten different ground motion records to determine the seismic performance of Steel, Steel-SMA and SMA RC buildings. Then fragility curves for each type of RC building by using IDA results for IO, LS and CP performance levels are calculated. Results obtained from the analyses indicate that 3-story frames have approximately the same spectral acceleration corresponding with failure of frames, but in the cases of 6 and 8-story frames, the spectral acceleration is higher in frames equipped with steel reinforcements. Furthermore, the probability of fragility in all frames increases by the building height for all performance levels. Finally, economic evaluation of the three systems are compared.