• Journal of the Earthquake Engineering Society of Korea
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• v.19 no.2
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• pp.45-53
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• 2015

This paper reviews the current seismic design code and research for dynamic earth pressure on retaining structures. Domestic design codes do not clearly define the estimation of dynamic earth pressure and give different comments for seismic coefficient, wall inertia and distribution of dynamic earth pressure using Mononobe-Okabe method. AASHTO has been revised reflecting current research and aims for effective seismic design. Various design codes are analyzed to compare their performance and economic efficiency. The results are used to make improvement of current domestic seismic design code. Further, it is concluded that the experimental investigation is also needed to verify and improve domestic seismic code for dynamic earth pressure.

• Geomechanics and Engineering
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• v.5 no.1
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• pp.37-55
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• 2013

An important issue in the design of soil-nailing systems, as long-term retaining walls, is to assess their stability during seismic events. As such, this study is aimed at simulating the dynamic behavior and failure pattern of nailed structures using two series of numerical analyses, namely dynamic time history and pseudo-static. These numerical simulations are performed using the Finite Difference Method (FDM). In order to consider the actual response of a soil-nailed structure, nonlinear soil behaviour, soil-structure interaction effects, bending resistance of structural elements and construction sequences have been considered in the analyses. The obtained results revealed the efficiency of both analysis methods in simulating the seismic failure mechanism. The predicted failure pattern consists of two sliding blocks enclosed by three slip surfaces, whereby the bottom nails act as anchors and the other nails hold a semi-rigid soil mass. Moreover, it was realized that an increase in the length of the lowest nails is the most effective method to improve seismic stability of soil-nailed structures. Therefore, it is recommended to first estimate the nails pattern for static condition with the minimum required static safety factor. Then, the required seismic stability can be obtained through an increase in the length of the lowest nails. Moreover, placement of additional long nails among lowest nails in existing nailed structures can be considered as a simple retrofitting technique in seismic prone areas.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.14 no.2
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• pp.41-48
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• 2018

In this study, the dynamic absorber and the damper are applied to improve the seismic performance of the piping system, and their quantitative effects on the piping system performance are examined. For this purpose, the response performances of piping system applied with the dynamic absorber/damper are compared with those of the original piping system. Firstly, the frequency response analyses of the piping system with the presence or the absence of dynamic absorber/damper are performed and these results are compared. It has been shown that the maximum acceleration response per the frequency of the piping system is considerably reduced by installing the dynamic absorber and the damper. Secondly, the seismic responses of the piping systems with and without dynamic absorber/damper are compared. As a result of the numerical analyses, it is confirmed that key responses are reduced by 17%-63% due to the installation of the dynamic absorber and damper. Finally, as a result of the seismic performance evaluation, it is confirmed that the HCLPF (High Confidence of Low Probability of Failure) seismic performances are increased by 1.22 to 2.70 times with respect to the failure modes with an aid of the dynamic absorber and damper.

• 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 Korean Society of Safety
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• v.31 no.4
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• pp.97-103
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• 2016

This study investigates effects of partially earth anchored cable system on the structural safety for a long-span cable-stayed bridge under dynamic loads such as seismic and wind load. For a three span cable-stayed bridge with a main span length of 810 m, two models are analyzed and compared; one is a bridge model with a self anchored cable system, the other is a bridge model with a partially earth anchored cable system. By performing multi-mode spectrum analysis for a prescribed seismic load and multi-mode buffeting analysis for a fluctuating wind component, the structural response of two models are compared. From results, the partially earth anchored cable system reduce the maximum pylon moment by 66% since earth anchored cables affect the natural frequencies of girder vertical modes and pylon longitudinal modes. In addition, the girder axial forces are decreased, specially the decrement of the axial force is large in seismic load, while girder moment is slightly increased. Thus, the partially earth anchored cable system is effective system not only on reduction of girder axial forces but also improvement of structural safety of a cable-stayed bridge under dynamic loads such as seismic and wind loads.

• Journal of the Earthquake Engineering Society of Korea
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• v.24 no.4
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• pp.169-178
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• 2020

In a previous paper, ambient vibration tests were conducted on a cable stayed bridge with resilient-friction base isolation systems (R-FBI) to extract the dynamic characteristics of the bridge and compare the results with a seismic analysis model. In this paper, a nonlinear seismic analysis model was established for analysis of the bridge to compare the difference in seismic responses between nonlinear time history analysis and multi-mode spectral analysis methods in the seismic design phase of cable supported bridges. Through these studies, it was confirmed that the seismic design procedures of the "Korean Highway Bridge Design Code (Limit State Design) for Cable Supported Bridges" is not suitable for cable supported bridges installed with R-FBI. Therefore, to reflect the actual dynamic characteristics of the R-FBI installed on cable-supported bridges, an improved seismic design procedure is proposed that applies the seismic analysis method differently depending on the seismic isolation effect of the R-FBI for each seismic performance level.

• Nuclear Engineering and Technology
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• v.54 no.5
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• pp.1712-1725
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• 2022

For improving the seismic performance of the nuclear power plant (NPP) piping system, attempts have been made to apply a dynamic absorber (DA). However, the current piping DA design method is limited because it cannot provide the globally optimum values for the target design seismic loading. Therefore, this study proposes a seismic time history analysis-based DA optimal design method for piping. To this end, the Kriging approach is introduced to reduce the numerical cost required for seismic time history analyses. The appropriate design of the experiment method is used to increase the efficiency in securing response data. A gradient-based method is used to efficiently deal with the multi-dimensional unconstrained optimization problem of the DA optimal design. As a result, the proposed method showed an excellent response reduction effect in several responses compared to other optimal design methods. The proposed method showed that the average response reduction rate was about 9% less at the maximum acceleration, about 5% less at the maximum value of the response spectrum, about 9% less at the maximum relative displacement, and about 4% less at the maximum combined stress compared to existing optimal design methods. Therefore, the proposed method enables an effective optimal DA design method for mitigating seismic response in NPP piping in the future.

• Journal of the Earthquake Engineering Society of Korea
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• v.8 no.2
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• pp.9-17
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• 2004

The seismic performance evaluation and retrofit process are very important in old existing bridges. If the result is not appropriate. then a retrofit process are required. Among various retrofit methods, the seismic isolation is a very useful method. because it can be applied by replacing old bridge bearings. In this study, the effectiveness of seismic isolation is rationally verified. For this purpose, two seismic isolations used widely are selected and non-linear static and dynamic analyses are performed. The responses of existing bridges are compared with those of retrofited bridges by seismic isolation bridge for earthquake of target level. and seismic performances are evaluated.

• Structural Engineering and Mechanics
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• v.45 no.6
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• pp.821-835
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• 2013

The acceleration that the electrical equipment experiences on a structure can be several times the ground acceleration. Currently, substation support structures are being designed according to ASCE (Substation Structure Design Guide 2008), without any consideration about effects of these structures on dynamic behavior of mounted equipment. In this paper, a parametric study is implemented in order to improve seismic design of candlestick substation structures based on this design guide. To do this, dynamic amplification factor (DAF) of different candlestick support-equipment combinations is evaluated and compared to the target DAF presented in IEEE STD 693 (2006). Based on this procedure, a new criterion is developed to restrict maximum acceleration at support-equipment intersection.

• Structural Monitoring and Maintenance
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• v.10 no.3
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• pp.243-260
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• 2023

Indonesia has had seismic codes for earthquake-resistant structures designs since 1970 and has been updated five times to the latest in 2019. In updating the Indonesian seismic codes, seismic hazard maps for design also update, and there are changes to the Peak Ground Acceleration (PGA). Indonesian seismic design uses the concept of building performance levels consisting of Immediate occupancy (IO), Life Safety (LS), and Collapse Prevention (CP). Related to this performance level, cases still found that buildings were damaged more than their performance targets after the earthquake. Based on the above issues, this study aims to analyze the performance of base isolation design on existing target buildings and analyze the seismic fragility for a case study in Indonesia. The target building is a prototype design 8-story medium-rise residential building using the reinforced concrete moment frame structure. Seismic fragility analysis uses Incremental Dynamic Analysis (IDA) with Nonlinear Time History Analysis (NLTHA) and eleven selected ground motions based on soil classification, magnitude, fault distance, and earthquake source mechanism. The comparison result of IDA shows a trend of significant performance improvement, with the same performance level target and risk category, the base isolation structure can be used at 1.46-3.20 times higher PGA than the fixed base structure. Then the fragility analysis results show that the fixed base structure has a safety margin of 30% and a base isolation structure of 62.5% from the PGA design. This result is useful for assessing existing buildings or considering a new building's performance.