• Journal of Korean Society of Coastal and Ocean Engineers
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• v.25 no.6
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• pp.412-421
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• 2013

Nowadays, small and medium-sized earthquakes occur frequently in the west coast of Korea. The earthquake induced damages on the harbor structure such as quay wall possibly make a severe impact on national economy. Therefore, not only a seismic design for the structures but warning system for seismic damage right after the occurrence of earthquake should be developed. In this study, seismic fragility analysis was performed to be given to earthquake damage prediction system for quay wall structures in Busan and Incheon harbor. Four types of structures such as pier-type, caisson type, counterfort type, block-type were analyzed and fragility curves of functional performance level and collapse prevention level based on displacement criteria were found. Regression analyses by using the results of the two ports were done for possible use in other port structures.

• Advances in concrete construction
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• v.9 no.4
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• pp.337-343
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• 2020

In the present study, by employing fragility analysis, the seismic vulnerability of a concrete girder bridge, one of the most common existing structural bridge systems, has been performed. To this end, drift demand model as a fundamental ingredient of any probabilistic decision-making analyses is initially developed in terms of the two most common intensity measures, i.e., PGA and Sa (T₁). Developing a probabilistic demand model requires a reliable database that is established in this paper by performing incremental dynamic analysis (IDA) under a set of 20 ground motion records. Next, by employing Bayesian statistical inference drift demand models are developed based on pre-collapse data obtained from IDA. Then, the accuracy and reasonability of the developed models are investigated by plotting diagnosis graphs. This graphical analysis demonstrates probabilistic demand model developed in terms of PGA is more reliable. Afterward, fragility curves according to PGA based-demand model are developed.

• Structural Engineering and Mechanics
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• v.83 no.3
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• pp.401-413
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• 2022

The collapse of civil infrastructure due to natural disasters results in financial losses and many casualties. In particular, the recent increase in earthquake activities has highlighted on the importance of assessing the seismic performance and predicting the seismic risk of a structure. However, the nonlinear behavior of a structure and the uncertainty in ground motion complicate the accurate seismic response prediction of a structure. Artificial intelligence can overcome these limitations to reasonably predict the nonlinear behavior of structures. In this study, a deep learning-based algorithm was developed to estimate the time-history seismic response of bridge structures. The proposed deep neural network was trained using structural and ground motion parameters. The performance of the seismic response prediction algorithm showed the similar phase and magnitude to those of the time-history analysis in a single-degree-of-freedom system that exhibits nonlinear behavior as a main structural element. Then, the proposed algorithm was expanded to predict the seismic response and fragility prediction of a bridge system. The proposed deep neural network reasonably predicted the nonlinear seismic behavior of piers and bearings for approximately 93% and 87% of the test dataset, respectively. The results of the study also demonstrated that the proposed algorithm can be utilized to assess the seismic fragility of bridge components and system.

• Earthquakes and Structures
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• v.5 no.6
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• pp.733-751
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• 2013

Near field ground motions have caused several structural damages in recent decades. As a result, seismic codes are being updated with related requirements. In this paper a comparative study on the seismic behavior of concentrically braced frames (CBFs) designed based on different seismic codes is performed. Reliability of various frames with different heights and bracing types are analyzed based on the results of "Incremental Dynamic Analysis" (IDA) under near field ground motions. Fragility curves corresponding to IO (Immediate Occupancy) and CP (Collapse Prevention) limit states are extracted based on IDA curves. Results imply that, frames designed based on the near field seismic design criteria of UBC-97 are more reliable under near field ground motions and their failure probability is less comparing to others.

• Journal of the Society of Disaster Information
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• v.7 no.3
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• pp.171-180
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• 2011

As a great earthquake hit east Japan recently, the interests for the necessity of earthquake resistant design and earthquake resistance ability of existent structures are much increased. The damage or collapse of a bridge, as a social overhead capital structure affects socially and economically. Thus the evaluation of earthquake resistance ability of these structures is very important. The reviewing methods for earthquake resistance ability are mostly deterministic. Although the deterministic methods are fit for the evaluation of safety of each member, they are not practical for the whole structure. For the evaluation of structural safety for earthquake, the method for the evaluation of fragility or damage is needed for some stages of damage. In this paper, fragility curves of steel box bridge using RFPB bearing for PGA, PGV, SA, SV, SI are constructed, and these are compared with the cases of FPB.

• Journal of the Earthquake Engineering Society of Korea
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• v.19 no.1
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• pp.29-36
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• 2015

Base isolation is considered as a seismic protective system in the design of next generation Nuclear Power Plants (NPPs). If seismic isolation devices are installed in nuclear power plants then the safety under a seismic load of the power plant may be improved. However, with respect to some equipment, seismic risk may increase because displacement may become greater than before the installation of a seismic isolation device. Therefore, it is estimated to be necessary to select equipment in which the seismic risk increases due to an increase in the displacement by the installation of a seismic isolation device, and to perform research on the seismic performance of each piece of equipment. In this study, modified NRC-BNL benchmark models were used for seismic analysis. The numerical models include representations of isolation devices. In order to validate the numerical piping system model and to define the failure mode, a quasi-static loading test was conducted on the piping components before the analysis procedures. The fragility analysis was performed by using the results of the inelastic seismic response analysis. Inelastic seismic response analysis was carried out by using the shell finite element model of a piping system considering internal pressure. The implicit method was used for the direct integration time history analysis. In addition, the collapse load point was used for the failure mode for the fragility analysis.

• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.6
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• pp.177-184
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• 2021

In recent years, large-scale earthquake activity has occurred in Korea, and thus public interest in earthquakes is increasing. Accordingly, the importance of seismic performance management of structures is emerging. In particular, the collapse of a bridge, one of main road facilities, directly leads to many casualties. Therefore, engineers need to evaluate the seismic fragility of the bridge and prepare for the earthquake event. The service life of these bridges has been over 30 years, which requires a study on the aging effect on bridges. In this study, seismic analysis of the target RC slab bridge was performed considering the aging effects of each component of the bridge. Components of the bridge included pier and bearing, which dominate the seismic response of the bridge. The seismic performance of the bridge was evaluated using nonlinear static and dynamic analyses. In addition, the limit state and dynamic response of each component were used to evaluate the seismic fragility according to the aging of each component.

• Smart Structures and Systems
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• v.22 no.4
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• pp.383-397
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• 2018

Traditional base isolation systems focus on isolating the seismic response of a structure in the horizontal direction. However, in regions where the vertical earthquake excitation is significant (such as near-fault region), a traditional base-isolated building exhibits a significant vertical vibration. To eliminate this shortcoming, a rocking-isolated system named Telescopic Column (TC) is proposed in this paper. Detailed rocking and isolation mechanism of the TC system is presented. The seismic performance of the TC is compared with the traditional elastomeric bearing (EB) and friction pendulum (FP) base-isolated systems. A 4-storey reinforced concrete moment-resisting frame (RC-MRF) is selected as the reference superstructure. The seismic response of the reference superstructure in terms of column axial forces, base shears, floor accelerations, inter-storey drift ratios (IDR) and collapse margin ratios (CMRs) are evaluated using OpenSees. The results of the nonlinear dynamic analysis subjected to multi-directional earthquake excitations show that the superstructure equipped with the newly proposed TC is more resilient and exhibits a superior response with higher margin of safety against collapse when compared with the same superstructure with the traditional base-isolation (BI) system.

• Steel and Composite Structures
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• v.42 no.1
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• pp.107-121
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• 2022

Past studies have shown that the aspect ratio (width-to-height) of a steel plate shear wall (SPSW) can significantly affect its seismic response. SPSWs with lower aspect ratio (narrow SPSW) may experience low lateral stiffness and flexure dominated drift response. As the height of the frame increases, the narrow SPSWs prove to be uneconomical and demonstrate inferior seismic response than their wider counterparts. Moreover, the thicker web plates required for narrow SPSWs exerts high inward pull on the VBEs. The present study suggests the limiting values of the aspect ratio for an SPSW system by evaluating the seismic collapse performance of 3-, 6- and 9-story SPSW systems using FEMA P695 methodology. For this purpose, nonlinear models are developed. These models are validated with the past quasi-static experimental results. Non-linear static analyses and Incremental dynamic analyses are then carried. The results are then utilized to conservatively suggest the limiting values of aspect ratios for SPSW system. In addition to the conventional-SPSW (Conv-SPSW), the collapse performance of staggered-SPSW (S-SPSW) is also explored. Its performance is compared with the Conv-SPSW and the use of S-SPSW is suggested in the cases where SPSW with lower than recommended aspect ratio is desired.

• Earthquakes and Structures
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• v.13 no.2
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• pp.151-164
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• 2017

This article aims to investigate the possible retrofitting of a deficient building with soft story failure mode by connecting it to an adjacent building which is designed based on current code with friction dampers at all floors. Low cost and high performance reliability along with significant energy dissipation pertaining to stable hysteretic loops may be considered in order to choose the proper damper for connecting adjacent buildings. After connecting two neighbouring floors by friction dampers, the sliding forces of dampers at various stories are set in two arrangements: uniform sliding force and then variable sliding force. In order to account for the stochastic nature of the seismic events, incremental dynamic analyses are employed prior and after the installation of the friction dampers at the various floors. Based on these results, fragility curves and mean annual rate of exceedance of serviceability and ultimate limit states are obtained. The results of this study show that the collapse mode of the deficient building can affect the optimum arrangement of sliding forces of friction dampers at Collapse Prevention (CP) performance level. In particular, the Immediate Occupancy (IO) performance level is not tangible to the sliding force arrangement and it depends solely on sliding force value. Generally it can be claimed that this rehabilitation scheme can turn the challenge of pounding two adjacent buildings into the opportunity of dissipating a large amount of the seismic input energy by the friction dampers, thus improving significantly the poor seismic performance of the deficient structure.