• 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 the Korea institute for structural maintenance and inspection
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• v.24 no.5
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• pp.77-85
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• 2020

In this study, the seismic fragility curve according to the boundary conditions is created for a two-pylon concrete cable-stayed bridge, and the effect of the boundary conditions on the seismic fragility of the target bridge is evaluated. An analysis model for the target bridge is constructed using Midas Civil, and a nonlinear time history analysis is performed by applying the fiber element, concrete and rebar material models. The boundary conditions between the pylon and the stiffened girder are classified into four types: rigid, unconstrained, pot bearing, and seismic isolation bearing, and the seismic fragility curves are created for each boundary condition. The plastic hinge section of the pylon, the connection part, and the cable are selected as weak members, and the earthquake vulnerability curve is created for them. As a result of the analysis, it is found that the seismic isolation bearing model shows the lowest damage probability in the pylon and the connection part, and the seismic fragility of the cable is less affected by the boundary conditions than other members.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.37 no.3
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• pp.151-162
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• 2024

As the incidence direction of ground motion (or seismic wave) changes, the seismic response of the structure will also change according to that direction. In order to analyze the effect of the seismic response of the example bridge according to the direction of incidence of ground motion, the acceleration response spectra (S_a-T1) corresponding to the 1-second period obtained for various angles of incidence were obtained. Using S_a-T1, 40 sets of orthogonal pairs of horizontal component seismic waves corresponding to 5 types of percentiles were generated. Seismic vulnerability analysis of the bridge piers was performed by obtaining the seismic response of an example bridge according to the direction of incidence of ground motion. By analyzing the seismic vulnerability analysis of seismic waves corresponding to five types of percentiles, it was found that the median value of the seismic vulnerability curve differs by about 1.2 to 2.6 times depending on the incident direction of the seismic wave. In other words, depending on the incidence direction of seismic waves, the degree of damage to the bridge structure can vary by about 1.2 to 2.6 times.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.9
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• pp.724-731
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• 2016

As the structural damage caused by earthquakes has been gradually increasing, estimating the seismic fragility of structures has become essential for earthquake preparation. Seismic fragility curves are widely used as a probabilistic indicator of structural safety against earthquakes, and many researchers have made efforts to develop them in a more accurate and effective manner. However, most of the previous research studies used simplified 2D analytical models when deriving fragility curves, mainly to reduce the numerical simulation time; however, in many cases 2D models are inadequate to accurately evaluate the seismic behavior of a structure and its seismic vulnerability. Thus, this study provides a way to derive more accurate, but still effective, seismic fragility curves by using 3D analytical models. In this method, the reliability analysis software, FERUM, is integrated with the structural analysis software, ZEUS-NL, enabling the automatic exchange of data between these two software packages, and the first order reliability method (FORM), which is not a sampling-based method, is utilized to calculate the structural failure probabilities. These tools make it possible to conduct structural reliability analyses effectively even with 3D models. By using the proposed method, this study conducted a seismic vulnerability assessment of RC frame structures with their 3D analytical models.

• Earthquakes and Structures
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• v.4 no.2
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• pp.157-179
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• 2013

Vulnerability studies on the existing building stock require that a large number of buildings is analyzed to obtain statistically significant evaluations of the seismic performance. Therefore, analytical evaluation methods need to be based on simplified methodologies of analysis which can afford the treatment of a large building population with a reasonable computational effort. Simplified Pushover-Based Earthquake Loss Assessment approach (SP-BELA), where a simplified methodology to identify the structural capacity of the building through the definition of a pushover curve is adopted, was developed on these bases. Main objective of the research work presented in this paper is to validate the simplified methodology implemented in SP-BELA against the results of more sophisticated nonlinear dynamic analyses (NLDAs). The comparison is performed for RC buildings designed only to vertical loads, representative of the "as built" in Italy and in Mediterranean countries with a building stock very similar to the Italian one. In NLDAs the non linear and degrading behaviour, typical of the structures under consideration when subjected to high seismic loads, is evaluated using models able to capture, with adequate accuracy, the non linear behaviour of RC structural elements taking into account stiffness degradation, strength deterioration, and pinching effect. Results show when simplified analyses are in good agreement with NLDAs. As a consequence, unsatisfactory results from simplified analysis are pointed out to address their current applicability limits.

• Journal of the Earthquake Engineering Society of Korea
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• v.27 no.2
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• pp.83-90
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• 2023

The recent increase in earthquake activities has highlighted the importance of seismic performance evaluation for civil infrastructures. In particular, the container crane essential to maintaining the national logistics system with port operation requires an exact evaluation of its seismic response. Thus, this study aims to assess the seismic vulnerability of container cranes considering their seismic characteristics. The seismic response of the container crane should account for the structural members' yielding and buckling, as well as the crane wheel's uplifting derailment in operation. The crane's yielding and buckling limit states were defined using the stress of crane members based on the load and displacement curve obtained from nonlinear static analysis. The derailment limit state was based on the height of the rail, and nonlinear dynamic analysis was performed to obtain the seismic fragility curves considering defined limit states and seismic characteristics. The yield and derailment probabilities of the crane in the near-fault ground motion were approximately 1.5 to 4.7 and 2.8 to 6.8 times higher, respectively, than those in the far-fault ground motion.

• Earthquakes and Structures
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• v.22 no.1
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• pp.15-23
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• 2022

One of the key tools in assessing the seismic vulnerability of the structures is the use of fragile functions, which is the possibility of damage from a particular damage surface for several levels of risk from the seismic movements of the earth. The aim of this study is to investigate the effect of two categories of earthquake events on the fragile curve (FRC) of the steel construction system. In this study, the relative lateral displacement of the structures is considered as a damage criterion. The limits set for modifying the relative lateral position in the HAZUS instruction are used to determine the failure modes, which include: slight, moderate, extensive and complete. The results show, as time strong-motion increases, the probability of exceeding (PoE) increases (for Peak ground acceleration (PGA) less than 0.5). The increase in seismic demand increases the probability of exceeding. In other words, it increases the probability of exceeding, if the maximum earthquake acceleration increases. Also, 7-storey model in extensive mode has 20 and 26.5% PoE larger than 5- and 3-storey models, respectively.

• Computers and Concrete
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• v.16 no.1
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• pp.99-123
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• 2015

In this study, structural vulnerability of reinforced concrete moment resisting frames (RC-MRFs) by considering the Iran-specific characteristics is investigated to manage the earthquake risk in terms of multicomponent seismic excitations. Low and medium rise RC-MRFs, which constitute approximately 80-90% of the total buildings stock in Iran, are focused in this fragility-based assessment. The seismic design of 3-12 story RC-MRFs are carried out according to the Iranian Code of Practice for Seismic Resistant Design of Buildings (Standard No. 2800), and the analytical models are formed accordingly in open source nonlinear platforms. Frame structures are categorized in three subclasses according to the specific characteristics of construction practice and the observed seismic performance after major earthquakes in Iran. Both far and near fields' ground motions have been considered in the fragility estimation. An optimal intensity measure (IM) called Sa, avg and beta probability distribution were used to obtain reliable fragility-based database for earthquake damage and loss estimation of RC buildings stock in urban areas of Iran. Nonlinear incremental dynamic analyses by means of lumped-parameter based structural models have been simulated and performed to extract the fragility curves. Approximate confidence bounds are developed to represent the epistemic uncertainties inherent in the fragility estimations. Consequently, it's shown that including vertical ground motion in the analysis is highly recommended for reliable seismic assessment of RC buildings.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.1
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• pp.175-182
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• 2008

In performing a risk analysis of structure for earthquake, it is imperative to identify the vulnerability of structures associated with various stages of damage. And the earthquake resisting capability is needed for structures like bridge. So the damage analysis of bridges with or without isolator for earthquake effects is necessary. In this paper, the risk analysis of seismic isolated LRB bridges considering earthquake effects such as PGA, PGV, SA, SV, and SI is performed using fragility curves to assure the earthquake resisting capability of the structures. And, the stability of fragility curve is investigated with respect to elastic modulus.

• Journal of the Korea institute for structural maintenance and inspection
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• v.13 no.2 s.54
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• pp.145-152
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• 2009

In performing a risk analysis on structure for earthquake, it is imperative to identify the vulnerability of structures associated with various stages of damage. And the earthquake resisting capability is needed for structures like bridge. So the damage analysis of bridges with or without isolator for earthquake effects is necessary. In this paper, the risk analysis of seismic isolated LRB bridges considering earthquake effects such as PGA, PGV, SA, SV, and SI is performed using fragility curves to assure the earthquake resisting capability of the structures. And, the stability of fragility curve is investigated with respect to input earthquake.