• Earthquakes and Structures
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• v.15 no.6
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• pp.605-616
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• 2018

In this paper, an extended Cloud analysis method is developed for seismic fragility assessment of existing highway bridges in the southeast Queensland region. This method extends the original Cloud analysis dataset by performing scaled Cloud analyses. The original and scaled Cloud datasets are then paired to generate seismic fragility curves. The seismic hazard in this region is critically reviewed, and the ground motion records are selected for the time-history analysis based on various record selection criteria. A parametric highway bridge model is developed in the OpenSees analysis software, and a sampling technique is employed to quantify the uncertainties of highway bridges ubiquitous in this region. Technical recommendations are also given for the seismic performance evaluation of highway bridges in such low-to-moderate seismic zones. Finally, a probabilistic fragility study is conducted by performing a total of 8000 time-history analyses and representative bridge fragility curves are generated. It is illustrated that the seismic fragility curves generated by the proposed extended Cloud analysis method are in close agreement with those which are obtained by the rigorous incremental dynamic analysis method. Also, it reveals that more than 50% of highway bridges existing in southeast Queensland will be damaged subject to a peak ground acceleration of 0.14 g.

• Structural Engineering and Mechanics
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• v.78 no.3
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• pp.333-350
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• 2021

Motivated by the demand of seismic protection of museum collections and development of performance-based seismic design guidelines, this paper investigates the seismic fragility of sliding artifacts based on incremental dynamic analysis and three-dimensional finite element model of the artifact-showcase-museum system considering nonlinear behavior of the structure and contact interfaces. Different intensity measures (IMs) for seismic fragility assessment of sliding artifacts are compared. The fragility curves of the sliding artifacts in both freestanding and restrained showcases placed on different floors of a four-story reinforced concrete frame structure are developed. The seismic sliding fragility of the artifacts within a real-world museum subjected to bi-directional horizontal ground motions is also assessed using the proposed IM and engineering demand parameter. Results show that the peak floor acceleration including only values initiating sliding is an efficient IM. Moreover, the sliding fragility estimate for the artifact in the restrained showcase increases as the floor level goes higher, while it may not be true in the freestanding showcase. Furthermore, the artifact is more prone to sliding failure in the restrained showcase than the freestanding showcase. In addition, the artifact has slightly worse sliding performance subjected to bi-directional motions than major-component motions.

• Journal of the Earthquake Engineering Society of Korea
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• v.27 no.6
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• pp.283-291
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• 2023

Unlike other facilities, maintaining processes is essential in industrial facilities. Pipe racks, which support pipes of various diameters, are important structures used in industrial facilities. Since the transport process of pipes directly affects the operation of industrial facilities, a fragility curve should be derived based on considering not only the pipe racks' structural safety but also the pipes' transport process. There are several studies where the fragility curves have been determined based on the structural behavior of pipe racks. However, few studies consider the damage criteria of pipes to ensure the transportation process, such as local buckling and tensile failure with surface defects. In this study, an analysis model of a typical straight pipe rack used in domestic industrial facilities is constructed, and incremental dynamic analysis using nonlinear response history analysis is performed to estimate the parameters of the fragility curve by the maximum likelihood estimation. In addition, the pipe rack's structural behavior and the pipe's damage criteria are considered the limit state for the fragility curve. The limit states considered in this paper to evaluate fragility curves are more reasonable to ensure the transportation process of the pipe systems.

• Journal of Korean Tunnelling and Underground Space Association
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• v.25 no.3
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• pp.187-200
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• 2023

This study analyzed the seismic fragility of bored tunnels based on their surrounding conditions and suggested a representative seismic fragility model. By analyzing the existed seismic fragility models developed for bored tunnels, we developed weighted combination models for each surrounding conditions, such as ground conditions and depth of the tunnel. The seismic fragility curves use the peak ground acceleration (PGA) as a parameter. When the PGA was 0.3 g, the probability of damage exceeding minor or slight damage was 20% for depth of 50 m or less, 10% for depth between 50 m and 100 m, and 3% for depth of 100 m or more. It was also found that the probability of damage was higher for the same PGA and depth when the surrounding ground was rock rather than soil. The probability of damage decreases as the depth increase. This study is expected to be used for developing a comprehensive seismic fragility function for tunnels in the future.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.35 no.3
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• pp.149-158
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• 2022

As a bridge ages, its mechanical properties and structural performance deteriorate, degrading its seismic performance during a strong earthquake. In this study, the aging of piers and bridge bearings was quantified in several stages and reflected in the analysis model, enabling the evaluation of the member-level seismic fragility of these bearings. Moreover, by assuming that the failure mechanism of a bridge system is a series system, a method for evaluating the system-level seismic fragility based on the member-level seismic fragility analysis result is formulated and proposed. For piers with rubber and lead-rubber bearings (members vulnerable to aging effects), five quantitative degrees of aging (0, 5, 10, 25, and 40%) are assumed to evaluate the member-level seismic fragility. Then, based on the result, the system-level seismic fragility evaluation was implemented. The pier rather than the bridge bearing is observed to have a dominant effect on the system-level seismic fragility. This means that the seismic fragility of more vulnerable structural members has a dominant influence on the seismic fragility of the entire bridge system.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2003.10a
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• pp.495-502
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• 2003

This study proposed the Probability Density Function (PDF) interpolation technique to evaluate the seismic fragility curves as a function of the return period. Seismic fragility curves have been developed as a function of seismic intensities such as peak ground acceleration, peak pound velocity, and pseudo-velocity spectrum. The return period of design earthquakes, however, can be more useful among those seismic intensity measurements, because the seismic hazard curves are generally represented with a return period of design earthquakes and the seismic design codes also require to consider the return period of design earthquake spectrum for a specific site. In this respect the PDF interpolation technique is proposed to evaluate the seismic fragility curves as a function of return period. Seismic fragility curves based on the return period are compared with ones based on the peak ground acceleration for the bridge model.

• Journal of the Earthquake Engineering Society of Korea
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• v.19 no.5
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• pp.207-217
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• 2015

In order to increase seismic performance of nuclear power plant (NPP) in strong seismic zone, lead-rubber bearing (LRB) can be applied to seismic isolation system of NPP structures. Simple equivalent linear model as structural analysis model of LRB is more widely used in initial design process of LRB than a bilinear model. Seismic responses for seismically isolated NPP containment structures subjected to earthquakes categorized into 5 different soil-site classes are calculated by both of the equivalent linear- and bilinear- LRB models and compared each others. It can be observed that the maximum displacements of LRB and shear forces of containment in the case of the equivalent linear LRB model are larger than those in the case of bilinear LRB model. From the seismic fragility curves of NPP containment structures isolated by LRB, it can be observed that seismic fragility in the case of equivalent linear LRB model are about 5~30 % larger than those in the case of bilinear LRB model.

• International Journal of High-Rise Buildings
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• v.9 no.2
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• pp.175-185
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• 2020

Currently, few studies have been conducted to comprehend the seismic reliability of post-tensioned (PT) CLT shear wall structures, due to the complexity of this kind of structural system as well as due to lack of a reliable structural model. In this paper, a set of 4-, 8-, 12-, and 16-storey benchmark PT CLT shear wall structures (PT-CLTstrs) were designed using the direct displacement-based design method, and their calibrated structural models were developed. The seismic reliability of each PT-CLTstr was assessed based on the fragility analysis and based on the response surface method (RSM), respectively. The fragility-based reliability index and the RSM-based reliability index were then compared, for each PT-CLTstr and for each seismic hazard level. Results show that the RSM-based reliabilities are slightly less than the fragility-based reliabilities. Overall, both the RSM and the fragility-based reliability method can be used as efficient approaches for assessing the seismic reliabilities of the PT-CLTstrs. For these studied mid- and high-rise benchmark PT-CLTstrs, following their fragility-based reliabilities, the 8-storey PT-CLTstr is subjected to the least seismic vulnerability; while, following their RSM-based reliabilities, the 4-storey PT-CLTstr is subjected to the least seismic vulnerability

• Structural Engineering and Mechanics
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• v.63 no.1
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• pp.47-53
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• 2017

The fundamental goal of this study is to minimize the uncertainty of the median fragility curve and to assess the structural vulnerability under earthquake excitation. Bayesian Inference with Markov Chain Monte Carlo (MCMC) simulation has been presented for efficient collapse response assessment of the independent intake water tower. The intake tower is significantly used as a diversion type of the hydropower station for maintaining power plant, reservoir and spillway tunnel. Therefore, the seismic fragility assessment of the intake tower is a pivotal component for estimating total system risk of the reservoir. In this investigation, an asymmetrical independent slender reinforced concrete structure is considered. The Bayesian Inference method provides the flexibility to integrate the prior information of collapse response data with the numerical analysis results. The preliminary information of risk data can be obtained from various sources like experiments, existing studies, and simplified linear dynamic analysis or nonlinear static analysis. The conventional lognormal model is used for plotting the fragility curve using the data from time history simulation and nonlinear static pushover analysis respectively. The Bayesian Inference approach is applied for integrating the data from both analyses with the help of MCMC simulation. The method achieves meaningful improvement of uncertainty associated with the fragility curve, and provides significant statistical and computational efficiency.

• Journal of Preventive Medicine and Public Health
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• v.47 no.6
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• pp.289-297
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• 2014

Objectives: This community-based cohort study was performed to investigate the incidence of and factors related to self-reported fragility fractures among middle-aged and elderly women living in rural Korea. Methods: The osteoporosis cohort recruited 430 women 40 to 69 years old in 1999, and 396 of these women were followed over 11 years. In 1999, questionnaires from all participants assessed general characteristics, medical history, lifestyle, menstrual and reproductive characteristics, and bone mineral density. In 2010, self-reported fractures and the date, site, and cause of these fractures were recorded. Cox proportional hazards models were used to calculate hazard ratios (HRs). Results: Seventy-six participants among 3949.7 person-years experienced fragility fractures during the 11-year follow-up. The incidence of fragility fractures was 1924.2 per 100 000 person-years (95% confidence interval [CI], 1491.6 to 2356.8). In the multivariate model, low body mass index (HR, 2.66; 95% CI, 1.13 to 6.24), a parental history of osteoporosis (HR, 2.03; 95% CI, 1.18 to 3.49), and postmenopausal status (HR, 3.50; 95% CI, 1.05 to 11.67) were significantly related to fragility fracture. Conclusions: Fracture prevention programs are needed among postmenopausal, rural, Korean women with a low body mass index and parental history of osteoporosis Korea.