• Earthquakes and Structures
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• v.15 no.3
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• pp.253-261
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• 2018

This article details a bridge-specific fragility method developed to enhance the seismic design and resilience of bridges. Current seismic design processes provide guidance for the design of a bridge that will not collapse during a design hazard event. However, they do not provide performance information of the bridge at different hazard levels or due to design changes. Therefore, there is a need for a supplement to this design process that will provide statistical information on the performance of a bridge, beyond traditional emphases on collapse prevention. This article proposes a bridge-specific parameterized fragility method to enable efficient estimation of various levels of damage probability for alternative bridge design parameters. A multi-parameter demand model is developed to incorporate bridge design details directly in the fragility estimation. Monte Carlo simulation and Logistic regression are used to determine the fragility of the bridge or bridge component. The resulting parameterized fragility model offers a basis for a bridge-specific design tool to explore the influence of design parameter variation on the expected performance of a bridge. When used as part of the design process, these tools can help to transform a prescriptive approach into a more performance-based approach, efficiently providing probabilistic performance information about a new bridge design. An example of the method and resulting fragility estimation is presented.

• Earthquakes and Structures
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• v.3 no.5
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• pp.767-781
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• 2012

The residual capacity against collapse of a main shock-damaged bridge can be coupled with the aftershock ground motion hazard to make an objective decision on its probability of collapse in aftershocks. In this paper, a steel tower suspension bridge with a main span of 2000 m is adopted for a case-study. Seismic responses of the bridge in longitudinal and transversal directions are analyzed using dynamic elasto-plastic finite displacement theory. The analysis is conducted in two stages: main shock and aftershocks. The ability of the main shock-damaged bridge to resist aftershocks is discussed. Results show that the damage caused by accumulated plastic strain can be ignored in the long-span suspension bridge. And under longitudinal and transversal seismic excitations, the damage is prone to occur at higher positions of the tower and the shaft-beam junctions. When aftershocks are not large enough to cause plastic strain in the structure, the aftershock excitation can be ignored in the seismic damage analysis of the bridge. It is also found that the assessment of seismic damage can be determined by superposition of damage under independent action of seismic excitations.

• The Journal of Asian Finance, Economics and Business
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• v.8 no.8
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• pp.1-12
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• 2021

Altman's Z-score is used to measure a company's financial health and to predict the probability that a company will collapse within 2 years. It is proven to be very accurate to forecast bankruptcy in a wide variety of contexts and markets. The goal of this study is to use Altman's Z-score model to forecast insolvency in non-financial publicly traded enterprises. Non-financial firms are a significant industry in Malaysia, and current trends of consolidation and long-term government subsidies make assessing the financial health of such businesses critical not just for the owners, but also for other stakeholders. The sample of this study includes 84 listed companies in the Kuala Lumpur Stock Exchange. Of the 84 companies, 52 are considered high risk, and 32 are considered low-risk companies. Secondary data for the analysis was gathered from chosen companies' financial reports. The findings of this study show that the Altman model may be used to forecast a company's financial collapse. It dispelled any reservations about the model's legitimacy and the utility of applying it to predict the likelihood of bankruptcy in a company. The findings of this study have significant consequences for investors, creditors, and corporate management. Portfolio managers may make better selections by not investing in companies that have proved to be in danger of failing if they understand the variables that contribute to corporate distress.

• Earthquakes and Structures
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• v.21 no.5
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• pp.477-487
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• 2021

This study focuses on the influence of strong ground motion duration on the response and collapse probability of reinforced concrete walls with a predominant response in flexure. Walls with different height and mass were used to account for a broad spectrum of configurations and fundamental periods. The walls were designed following the specifications of the Chilean design code. Non-linear models of the reinforced concrete walls using a distributed plasticity approach were performed in OpenSees and calibrated with experimental data. Special attention was put on modeling strength and stiffness degradation. The effect of duration was isolated using spectrally equivalent ground motions of long and short duration. In order to assess the behavior of the RC shear walls, incremental dynamic analyses (IDA) were performed, and fragility curves were obtained using cumulative and non-cumulative engineering demand parameters. The spectral acceleration at the fundamental period of the wall was used as the intensity measure (IM) for the IDAs. The results show that the long duration ground motion set decreases the average collapse capacity in walls of medium and long periods compared to the results using the short duration set. Also, it was found that a lower median intensity is required to achieve moderate damage states in the same medium and long period wall models. Finally, strength and stiffness degradation are important modelling parameters and if they are not included, the damage in reinforced concrete walls may be greatly underestimated.

• The Bulletin of The Korean Astronomical Society
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• v.46 no.2
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• pp.80.1-80.1
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• 2021

Intensive Monitoring Survey of Nearby Galaxies (IMSNG) is a program monitoring nearby galaxies with a high cadence within a day. The main goal of the project is to constrain the SNe explosion mechanism and properties of their progenitors by catching the early lights from the shock-heated cooling emission. The observation campaign began in 2014 with two 1-m class telescopes in the northern hemisphere. Now more than ten telescopes are monitoring galaxies with 60 IMSNG targets, which have a high probability of supernova explosion every night all around the world. Since the project started, the following observations have been carried out on 14 SNe Ia(including -pec), 27 core-collapse supernovae (CCSNe), and around 40 transients in other types. In this poster, we present the current status of IMSNG SNe data first and then focus more on the CCSNe. CCSNe are the explosion of massive stars, more massive than eight times of the Sun. They have been studied for more than a half decades but still have key questions to be solved, such as distinct types, the characteristics driving their diversity, and so on. Here, we show our ongoing studies of CCSNe in IMSNG, focusing on their usefulness as distance indicators and properties of early light curves.

• Earthquakes and Structures
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• v.25 no.5
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• pp.343-358
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• 2023

The superelastic viscous damper (SVD) is a hybrid passive control device comprising a viscoelastic damper and shape memory alloy (SMA) cables connected in series. The SVD is an innovative damper through which a large amount of seismic energy can dissipate. The current study assessed the seismic collapse induced by steel moment-resisting frames (SMRFs) equipped with SVDs and compared them with the performance of special MRFs and buckling restrained brace frames (BRBFs). For this purpose, nonlinear dynamic and incremental dynamic analysis (IDA) were conducted in OpenSees software. Both 5- and 9-story special MRFs, BRBFs, and MRFs equipped with the SVDs were examined. The results indicated that the annual exceedance rate for maximum residual drifts of 0.2% and 0.5% for the BRBFs and MRFs with SVDs, respectively, were considerably less than for SMRFs with reduced-beam section (RBS) connections and that the seismic performances of these structures were enhanced with the use of the BRB and SVD. The probability of collapse due to residual drift in the SVD, BRB, and RBS frames in the 9-story structure was 1.45, 1.75, and 1.05 times greater than for the 5-story frame.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.13 no.4
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• pp.217-226
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• 1993

This study is related to the surface subsidence due to the collapse of a underground void during earthquakes. The amount of the settlement due to the collapse of a underground void will depend on the depth of the void, the initial condition of unit weight of sand, the size and type of foundation, the strength of earthquake, the size of a void, etc. The purpose of the paper is to estimate the amount of the subsidence, analyse the factors affecting the subsidence, and develop a program determining the probability of the damages to structures in terms of absolute and differential settlement and rotational settlement. On the base of the results obtained in this study, when the depth of a void is constant and the width of the void increases, the change of the subsidence factor due to the angle of internal friction and the actual effective factor of the void become smaller than that due to the unit weight of sand deposits. In the same condition, the probabilities of damages due to the absolute and differential settlement increase, and those due to the rotational settlement decrease.

• Journal of Korean Society of Steel Construction
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• v.29 no.5
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• pp.369-376
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• 2017

This paper is the sequel of a companion paper (I. Seismic Design) for design and assessment of the torsional irregular structure using ASCE 7-10 criteria. This study evaluates the influence of torsional provisions on the performance of the designed steel moment frame with different eccentricity, taking the collapse probability as performance metric using the methodology in FEMA P695. The result show that torsional irregular structure designed according to ASCE 7-10 has an excessive seismic performance and the collapse strength is low as the eccentricity increases. To make the design reasonable, a new design approach is proposed in this study.

• Journal of the Society of Naval Architects of Korea
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• v.28 no.2
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• pp.251-267
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• 1991

Plastic strength analysis using plastic failure mode as a limit state is adopted instead of a conventional elastic structural analysis to predict the ultimate strength of Web frame idealized by a plane frame. Linear programming arid Compact procedure are developed for determining the collapse load factor. It is found that the final results are good agreement with the results of Elasto-plastic analysis. Besides, the redundant structures like Web frame is known to have multiple failure modes. Web frame may collapse under any of the possible failure modes. Thus, the identification of these possible failure modes is necessary and very important in the reliability analysis of Web frame. In order to deal with multiple failure modes, automatic generation method of all failure modes and basic failure modes is used for selecting the dominant failure modes. The probability of failure pastic collapse of Web frame is calculated using these dominant failure modes. The safety of Web frame is asscssed and compared by performing the deterministic and probabilistic analysis.

• Earthquakes and Structures
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• v.21 no.5
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• pp.531-549
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• 2021

Analytical models were developed and seismic behaviors were analyzed for a three-story stone pagoda at the Cheollyongsa temple site, which was damaged by the Gyeongju earthquake of 2016. Both finite and discrete element modeling were used and the analysis results were compared to the actual earthquake damage. Vulnerable parts of stone pagoda structure were identified and their seismic behaviors via sliding, rocking, and risk analyses were verified. In finite and discrete element analyses, the 3F main body stone was displaced uniaxially by 60 and 80 mm, respectively, similar to the actual displacement of 90 mm resulting from the earthquake. Considering various input conditions such as uniaxial excitation and soil-structure interaction, as well as seismic components and the distance from the epicenter, both models yielded reasonable and applicable results. The Gyeongju earthquake exhibited extreme short-period characteristics; thus, short-period structures such as stone pagodas were seriously damaged. In addition, we found that sliding occurred in the upper parts because the vertical load was low, but rocking predominated in the lower parts because most structural members were slender. The third-floor main body and roof stones were particularly vulnerable because some damage occurred when the sliding and rocking limits were exceeded. Risk analysis revealed that the probability of collapse was minimal at 0.1 g, but exceeded 80% at above 0.3 g. The collapse risks at an earthquake peak ground acceleration of 0.154 g at the immediate occupancy, life safety, and collapse prevention levels were 90%, 52%, and 6% respectively. When the actual damage was compared with the risk analysis, the stone pagoda retained earthquake-resistant performance at the life safety level.