A new methodology of the development of seismic fragility curves

이영주,Do-Soo Moon 국제구조공학회 2014 Smart Structures and Systems, An International Jou Vol.14 No.5

There are continuous efforts to mitigate structural losses from earthquakes and manage risk through seismic risk assessment; seismic fragility curves are widely accepted as an essential tool of such efforts. Seismic fragility curves can be classified into four groups based on how they are derived: empirical, judgmental, analytical, and hybrid. Analytical fragility curves are the most widely used and can be further categorized into two subgroups, depending on whether an analytical function or simulation method is used. Although both methods have shown decent performances for many seismic fragility problems, they often oversimplify the given problems in reliability or structural analyses owing to their built-in assumptions. In this paper, a new method is proposed for the development of seismic fragility curves. Integration with sophisticated software packages for reliability analysis (FERUM) and structural analysis (ZEUS-NL) allows the new method to obtain more accurate seismic fragility curves for less computational cost. Because the proposed method performs reliability analysis using the first-order reliability method, it provides component probabilities as well as useful byproducts and allows further fragility analysis at the system level. The new method was applied to a numerical example of a 2D frame structure, and the results were compared with those by Monte Carlo simulation. The method was found to generate seismic fragility curves more accurately and efficiently. Also, the effect of system reliability analysis on the development of seismic fragility curves was investigated using the given numerical example and its necessity was discussed.

A new methodology of the development of seismic fragility curves

Lee, Young-Joo,Moon, Do-Soo Techno-Press 2014 Smart Structures and Systems, An International Jou Vol.14 No.5

There are continuous efforts to mitigate structural losses from earthquakes and manage risk through seismic risk assessment; seismic fragility curves are widely accepted as an essential tool of such efforts. Seismic fragility curves can be classified into four groups based on how they are derived: empirical, judgmental, analytical, and hybrid. Analytical fragility curves are the most widely used and can be further categorized into two subgroups, depending on whether an analytical function or simulation method is used. Although both methods have shown decent performances for many seismic fragility problems, they often oversimplify the given problems in reliability or structural analyses owing to their built-in assumptions. In this paper, a new method is proposed for the development of seismic fragility curves. Integration with sophisticated software packages for reliability analysis (FERUM) and structural analysis (ZEUS-NL) allows the new method to obtain more accurate seismic fragility curves for less computational cost. Because the proposed method performs reliability analysis using the first-order reliability method, it provides component probabilities as well as useful byproducts and allows further fragility analysis at the system level. The new method was applied to a numerical example of a 2D frame structure, and the results were compared with those by Monte Carlo simulation. The method was found to generate seismic fragility curves more accurately and efficiently. Also, the effect of system reliability analysis on the development of seismic fragility curves was investigated using the given numerical example and its necessity was discussed.

A New Method for Developing Seismic Collapse Fragility Curves Grounded on State-Based Philosophy

Aref Baharvand,Abdolrasoul Ranjbaran 한국강구조학회 2020 International Journal of Steel Structures Vol.20 No.2

Since the current process to achieve the collapse fragility curve in practical applications seems too complicated, also time-consuming to dominant by structure designers, the focus of this study is on introducing of a new approach for establishing collapse fragility curves which requires less analytical effort. To achieve this goal, state-based philosophy (SBP) has been taken into consideration. This theory benefits from some similarities in the nature of every failure process in solid mechanics regardless of its source. In this study these similarities are used intelligently in procedure of formulating new fragility function which has couple of unknown parameters. Next, it will be shown that these parameters can be attained from two different sources: the pushover curves of the structure, some selective damage data from incremental dynamic analysis analyses. Finally a complete form of new collapse fragility function which is called "SBP fragility function" proposed as a substitute for conventional collapse fragility function. The most important advantage of this new fragility function is its non-probabilistic structure that will make a huge difference in the amount of effort required to achieve the fragility curves. In this research, in order to ensure the efficiency, accuracy of this fragility function all steps of SBP fragility analyses are done on some special moment frames models, their results are presented.

Seismic Fragility Functions Grounded on State-Based Philosophy: Application to Low to Midrise Steel Frame Buildings

Aref Baharvand,Abdolrasoul Ranjbaran 대한토목학회 2020 KSCE Journal of Civil Engineering Vol.24 No.6

In this study, a new formulation for structural fragility function based on the theory of state-based philosophy (SBP) is introduced. In this innovative approach, gradual changes in stiffness (or flexibility) of the structure is considered as a firm base for describing changes in the state of the structure due to damage from various sources. In this study, the source of damage data is considered ground motions. After formulating state changes by using SBP theory, a new fragility function is proposed. Therefore, this new function is based on observations of various failure stages of the structure and, besides, it is organized specifically for the structural damage data. In order to prove the accuracy of this method, some special moment frames (SMFs) are modeled, and incremental dynamic analysis (IDA) is performed on them. Thus damage data are provided as initial input to the fragility function. After that, the final results of the SBP fragility function are compared with the results of the conventional methods of plotting the fragility curve, and lastly, the fragility curve's accuracy obtained by using this new function is verified. This new fragility function is called ‘SBP fragility function’ and has some advantages over the ordinary fragility functions, which are discussed in this article.

매설가스배관의 지진 취약도 해석

이도형,전정문,오장균,이두호 한국지진공학회 2010 한국지진공학회논문집 Vol.14 No.5

본 연구에서는 국내에서 널리 사용되고 있는 매설가스배관인 API X65에 대해 지진 취약도 해석을 수행하였다. 이를 위해, 15가지 경우의 배관 해석모델에 대해 12본 세트의 다양한 지진파를 0.1g 등간격으로 스케일링하여 비선형 시간이력해석을 수행한 후, 비선형 시간이력해석으로 얻어진 매설가스배관의 최대 변형률을 이용하여 지진취약도 해석을 수행하였다. 지진 취약도 해석을 위해 본 연구에서는 또한, 지반조건, 단부지점조건, 매립깊이 및 배관형태 등을 변수로 고려하여 지진 취약도 해석을 수행하였다. 지진 취약도 해석결과, 지반조건, 단부지점조건 및 매립깊이는 매설가스배관의 취약도 곡선에 영향을 끼치는 것으로 판단되었고, 특히 지반조건이 미치는 영향은 다른 두 변수에 비해 다소 큰 것을 확인할 수 있었다. 반면에, 배관형태가 취약도 곡선에 미치는 영향은 미미한 것을 알 수 있었다. 종합적으로, 매설가스배관의 지진 취약도 해석과 관련된 연구가 많지 않은 현실을 감안할 때, 본 연구결과는 매설가스배관의 지진 취약성 평가해석에 초석으로 고려되어질 수 있고, 추후 관련분야 연구에 좋은 참고자료가 될 것으로 사료된다. In this paper, earthquake fragility analysis has been comparatively performed with regard to a buried gas pipeline of API X65 which has been widely used in Korea. For this purpose, a nonlinear time-history analyses has been carried out for 15 different analytical models of a buried gas pipeline in terms of the selected 12 sets of earthquake ground motions with 0.1g of scaling interval. Following that, earthquake fragility analyses have been conducted using the maximum axial strain of the pipeline obtained from the nonlinear time-history analyses. Parameters under consideration for subsequent earthquake fragility analyses are soil conditions, end-restraint conditions, burial depth and the type of pipeline. Comparative analyses reveal that whereas the first three parameters influence the fragility curves, particularly soil conditions amongst the three parameters, the last parameter has a little effect on the curves. In all, the present study can be considered as a benchmark fragility analysis of a buried gas pipeline in the absence of an earthquake fragility analysis of the pipeline and thus is expected to be a useful source regarding earthquake fragility analyses of a buried gas pipelines.

PSC 상자형교의 지진취약도 곡선에 대한 근거리 및 원거리 지진의 영향

김학수,송종걸 한국지진공학회 2010 한국지진공학회논문집 Vol.14 No.5

구조물의 지진취약도 곡선은 지진의 다양한 강도를 최대지반가속도 등의 함수로 하여 몇 가지로 구분된 손상상태를 초과할 확률을 나타내는 것으로 구조물의 내진성능과 지진위험도를 평가하는데 유용하게 활용된다. 기존의 많은 연구자들이 수행한 지진취약도 곡선에 대한 연구에서 근거리 및 원거리 지진하중의 특성에 대하여 고려하지 못하였다. 본 연구에서는 근거리 및 원거리 지진으로 구분되는 지진가속도 기록을 사용하여 국내 교량의 대표적인 형식의 하나인 PSC상자형교에 대한 지진취약도 곡선을 평가하였으며 근거리와 원거리로 구분된 지진 특성이 지진취약도 곡선에 미치는 영향을 분석하였다. 예제교량의 지진취약도 곡선에 대한 근거리 및 원거리 지진의 영향이 현저한 차이를 나타내므로 지진취약도 해석시 근거리와 원거리로 구분되는 지진의 특성을 반영하여야 할 것이다. Seismic fragility curves of structures represent the probability of exceeding the prescribed structural damage state for a given various levels of ground motion intensity, such as peak ground acceleration (PGA). This means that seismic fragility curves are essential to the evaluation of structural seismic performance and assessments of risk. Most of existing studies have not considered the near- and far-fault earthquake effect on the seismic fragility curves. In order to evaluate the effect of near- and far-fault earthquakes, seismic fragility curves for PSC box girder bridges subjected to near- and far-fault earthquakes are calculated and compared. The seismic fragility curves are strongly dependent on the earthquake characteristics such as fault distance. This paper suggests that the effect of near- and far-fault earthquakes on seismic fragility curves of PSC box girder bridge structure should be considered.

Fragility Assessment for Electric Cabinet in Nuclear Power Plant Using Response Surface Methodology

Thanh-Tuan Tran,Anh-Tuan Cao,Thi-Hong-Xuyen Nguyen,김두기 한국원자력학회 2019 Nuclear Engineering and Technology Vol.51 No.3

An approach for collapse risk assessment is proposed to evaluate the vulnerability of electric cabinet innuclear power plants. The lognormal approaches, namely maximum likelihood estimation and linearregression, are introduced to establish the fragility curves. These two fragility analyses are applied for thenumerical models of cabinets considering various boundary conditions, which are expressed by representingrestrained and anchored models at the base. The models have been built and verified using thesystem identification (SI) technique. The fundamental frequency of the electric cabinet is sensitivebecause of many attached devices. To bypass this complex problem, the average spectral accelerationðSaÞ in the range of period that cover the first mode period is chosen as an intensity measure on thefragility function. The nonlinear time history analyses for cabinet are conducted using a suite of 40ground motions. The obtained curves with different approaches are compared, and the variability of riskassessment is evaluated for restrained and anchored models. The fragility curves obtained for anchoredmodel are found to be closer each other, compared to the fragility curves for restrained model. It is alsofound that the support boundary conditions played a significant role in acceleration response of cabinet.

Fragility assessment of RC-MRFs under concurrent vertical-horizontal seismic action effects

Ehsan Noroozinejad Farsangi,Abbas Ali Tasnimi,Babak Mansouri 사단법인 한국계산역학회 2015 Computers and Concrete, An International Journal Vol.16 No.1

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.

Component fragility assessment of a long, curved multi-frame bridge: Uniform excitation versus spatially correlated ground motions

Jeon, Jong-Su,Shafieezadeh, Abdollah,DesRoches, Reginald Techno-Press 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.65 No.5

This paper presents the results of an assessment of the seismic fragility of a long, curved multi-frame bridge under multi-support earthquake excitations. To achieve this aim, the numerical model of columns retrofitted with elliptical steel jackets was developed and validated using existing experimental results. A detailed nonlinear numerical model of the bridge that can capture the inelastic response of various components was then created. Using nonlinear time-history analyses for a set of stochastically generated spatially variable ground motions, component demands were derived and then convolved with new capacity-based limit state models to obtain seismic fragility curves. The comparison of failure probabilities obtained from uniform and multi-support excitation analyses revealed that the consideration of spatial variability significantly reduced the median value of fragility curves for most components except for the abutments. This observation indicates that the assumption of uniform motions may considerably underestimate seismic demands. Moreover, the spatial correlation of ground motions resulted in reduced dispersion of demand models that consequently decreased the dispersion of fragility curves for all components. Therefore, the spatial variability of ground motions needs to be considered for reliable assessment of the seismic performance of long multi-frame bridge structures.

Component fragility assessment of a long, curved multi-frame bridge: Uniform excitation versus spatially correlated ground motions

전종수,Abdollah Shafieezadeh,Reginald DesRoches 국제구조공학회 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.65 No.5

This paper presents the results of an assessment of the seismic fragility of a long, curved multi-frame bridge under multi-support earthquake excitations. To achieve this aim, the numerical model of columns retrofitted with elliptical steel jackets was developed and validated using existing experimental results. A detailed nonlinear numerical model of the bridge that can capture the inelastic response of various components was then created. Using nonlinear time-history analyses for a set of stochastically generated spatially variable ground motions, component demands were derived and then convolved with new capacity-based limit state models to obtain seismic fragility curves. The comparison of failure probabilities obtained from uniform and multi-support excitation analyses revealed that the consideration of spatial variability significantly reduced the median value of fragility curves for most components except for the abutments. This observation indicates that the assumption of uniform motions may considerably underestimate seismic demands. Moreover, the spatial correlation of ground motions resulted in reduced dispersion of demand models that consequently decreased the dispersion of fragility curves for all components. Therefore, the spatial variability of ground motions needs to be considered for reliable assessment of the seismic performance of long multi-frame bridge structures.