On the Seismic Fragility Assessment of Concrete Gravity Dams in Eastern Canada

2019 ◽  
Vol 35 (1) ◽  
pp. 211-231 ◽  
Author(s):  
Rocio Segura ◽  
Carl Bernier ◽  
Ricardo Monteiro ◽  
Patrick Paultre
Keyword(s):  
Ground Motion ◽  
Fragility Curves ◽  
Limit State ◽  
Selection Method ◽  
Probabilistic Methods ◽  
Fragility Analysis ◽  
Gravity Dams ◽  
Limit States ◽  
Eastern Canada

In recent years, probabilistic methods, such as fragility analysis, have emerged as reliable tools for the seismic assessment of dam-type structures. These methods require the selection of a representative suite of ground motion records, resulting in the need for a ground motion selection method that includes all the relevant ground motion parameters in the fragility analysis of this type of structure. This article presents the development of up-to-date fragility curves for the sliding limit states of gravity dams in Eastern Canada using a record selection method based on the generalized conditional intensity measure approach. These fragility functions are then combined with the recently developed regional hazard data to evaluate the annual risk, which is measured in terms of the unconditional probability of limit state exceedance. The proposed methodology is applied to a case study dam in northeastern Canada, whose fragility is assessed through comparison with previous studies and current safety guidelines. It is observed that the more accurate procedure proposed herein produces less conservative fragility estimates for the case study dam.

scholarly journals Modelling and Characterizing a Concrete Gravity Dam for Fragility Analysis

2019 ◽  
Vol 4 (4) ◽  
pp. 62 ◽  
Author(s):  
Segura Rocio L. ◽  
Bernier Carl ◽  
Durand Capucine ◽  
Patrick Paultre
Keyword(s):  
Earthquake Engineering ◽  
Seismic Vulnerability ◽  
Fragility Curves ◽  
Fragility Analysis ◽  
Past Century ◽  
Concrete Gravity Dam ◽  
Gravity Dams ◽  
Eastern Canada ◽  
Safety Guidelines

Most gravity dams have been designed and built during the past century with methods of analysis that are now considered inadequate. In recent decades, knowledge of seismology, structural dynamics and earthquake engineering has greatly evolved, leading to the evaluation of existing dams to ensure public safety. This study proposes a methodology for the proper modelling and characterisation of the uncertainties to assess the seismic vulnerability of a dam-type structure. This study also includes all the required analyses and verifications of the numerical model prior to performing a seismic fragility analysis and generating the corresponding fragility curves. The procedure presented herein also makes it possible to account for the uncertainties associated with the modelling parameters as well as the randomness in the seismic solicitation. The methodology was applied to a case study dam in Eastern Canada, whose vulnerability was assessed against seismic events with characteristics established by the current safety guidelines.

scholarly journals Dynamic Damage Mechanism and Seismic Fragility Analysis of an Aqueduct Structure

2021 ◽  
Vol 11 (24) ◽  
pp. 11709
Author(s):  
Xinyong Xu ◽  
Xuhui Liu ◽  
Li Jiang ◽  
Mohd Yawar Ali Khan
Keyword(s):  
Ground Motion ◽  
Structural Damage ◽  
Large Scale ◽  
Seismic Analysis ◽  
Fragility Curves ◽  
Limit State ◽  
Fragility Analysis ◽  
Seismic Fragility ◽  
Exceedance Probability ◽  
Computation Efficiency

The Concrete Damaged Plasticity (CDP) constitutive is introduced to study the dynamic failure mechanism and the law of damage development to the aqueduct structure during the seismic duration using a large-scale aqueduct structure from the South-to-North Water Division Project (SNWDP) as a research object. Incremental dynamic analysis (IDA) and multiple stripe analysis (MSA) seismic fragility methods are introduced. The spectral acceleration is used as the scale of ground motion record intensity measure (IM), and the aqueduct pier top offset ratio quantifies the limit of structural damage measure (DM). The aqueduct structure’s seismic fragility evaluation curves are constructed with indicators of different seismic intensity measures to depict the damage characteristics of aqueduct structures under different seismic intensities through probability. The results show that penetrating damage is most likely to occur on both sides of the pier cap and around the pier shaft in the event of a rare earthquake, followed by the top of the aqueduct body, which requires the greatest care during an earthquake. The results of two fragility analysis methodologies reveal that the fragility curves are very similar. The aqueduct structure’s first limit state level (LS1) is quite steep and near the vertical line, indicating that maintaining the excellent condition without damage in the seismic analysis will be challenging. Except for individual results, the overall fragility results are in good agreement, and the curve change rule is the same. The exceedance probability in the case of any ground motion record IM may be estimated using only two factors when using the MSA approach, and the computation efficiency is higher. The study of seismic fragility analysis methods in this paper can provide a reference for the seismic safety evaluation of aqueducts and similar structures.

scholarly journals Probability Calibration Of Load Duration Modification Factor For Timber Roofs In The Polish Mountain Zones

2014 ◽  
Vol 60 (2) ◽  
pp. 195-208
Author(s):  
T. Domański
Keyword(s):  
Limit State ◽  
High Stress ◽  
Life Time ◽  
Probabilistic Methods ◽  
Limit States ◽  
Term Limit ◽  
Load Duration ◽  
Maximum Likelihood Methods ◽  
Short And Long Term

Abstract The resistance parameters of timber structures decrease with time. It depends on the type of load and timber classes. Strength reduction effects, referred to as creep-rupture effects, due to long term loading at high stress ratio levels are known for many materials. Timber materials are highly affected by this reduction in strength with duration of load. Characteristic values of load duration and load duration factors are calibrated by means of using probabilistic methods. Three damage accumulation models are considered, that is Gerhard [1] model, Barret, Foschi[2] and Foshi Yao [3] models. The reliability is estimated by means of using representative short- and long-term limit states. Time variant reliability aspects are taken into account using a simple representative limit state with time variant strength and simulation of whole life time load processes. The parameters in these models are fitted by the Maximum Likelihood Methods using the data relevant for Polish structural timber. Based on Polish snow data over 45 years from mountain zone in: Zakopane – Tatra, Świeradów – Karkonosze, Lesko – Bieszczady, the snow load process parameters have been estimated. The reliability is evaluated using representative short – and long –term limit states, load duration factor kmod is obtained using the probabilistic model.

scholarly journals Probability calibration of deformation factor for timber roofs in the Polish mountain zones

2018 ◽  
Vol 163 ◽  
pp. 07003
Author(s):  
Tomasz Domański ◽  
Kamil Kmiecik
Keyword(s):  
Limit State ◽  
High Stress ◽  
Life Time ◽  
Probabilistic Methods ◽  
Limit States ◽  
Term Limit ◽  
Load Duration ◽  
Maximum Likelihood Methods ◽  
Short And Long Term

The resistance parameters of timber material structures decrease with time, depending on the type of load and timber classes. Strength and Modulus of Elasticity reduction effects, referred to as creeprupture effects, due to long term loading at high stress ratio levels are known for many materials. Timber materials are highly affected by this reduction in strength and deflection with duration of load. Characteristic values of load duration and deformation factors are calibrated by means of using probabilistic methods. The reliability is estimated by means of using representative short-and long-term limit states. Time variant reliability aspects are taken into account using a simple representative limit state with time variant strength and simulation of whole life time load processes. The parameters in these models are fitted by the Maximum Likelihood Methods using the data relevant for Polish structural timber . Based on Polish snow data over 45 years from mountain zones in: Zakopane – Tatra, Świeradów – Karkonosze, Lesko – Bieszczady, the snow load process parameters have been estimated. The reliability is evaluated using representative short – and long –term limit states. The deformation factor kdef is obtained using the probabilistic model.

Reliability of Burst Limit States for Damaged and Corroded High Strength Pipelines

2006 ◽  
Author(s):  
Marc A. Maes ◽  
Mamdouh M. Salama ◽  
Markus Dann
Keyword(s):  
Limit State ◽  
High Strength Steels ◽  
High Strength ◽  
Crack Arrest ◽  
Limit States ◽  
Lower Strain ◽  
Margin Of Safety ◽  
Normal Strength ◽  
The Impact

High strength steels (X100 and X120) that are being considered for high pressure gas pipelines differ from conventional steels by exhibiting lower work hardening capacity, lower strain to failure and softening of their HAZ. These differences impact burst limit state and tensile limit state, in addition to crack arrest. In this paper, the impact of the variations in mechanical properties on the reliability of pipe limit states involving ductile burst of damaged or corroded pipe is examined. The paper presents the results of burst limit state analysis using state-of-the-art plastic burst models of strain hardening pipe and considering all the uncertainties that impact the margin of safety of pipes subject to internal pressure. Intact pipes, corroded pipes and externally damaged pipes are considered. A case study comparing the differences between normal strength (X60) pipeline and high strength (X100) pipeline is also presented.

Analytical Fragility Curves for Ordinary Highway Bridges in Turkey

2011 ◽  
Vol 27 (4) ◽  
pp. 971-996 ◽  
Author(s):  
Özgür Avşar ◽  
Ahmet Yakut ◽  
Alp Caner
Keyword(s):  
Nonlinear Response ◽  
Fragility Curves ◽  
Ground Motions ◽  
Limit State ◽  
Highway Bridges ◽  
Skew Angle ◽  
Limit States ◽  
Point Estimates ◽  
Single Column ◽  
Skew Angles

This study focuses on the development of analytical fragility curves for the ordinary highway bridges constructed after the 1990s. Four major bridge classes were employed based on skew angle, number of columns per bent, and span number (only multispan bridges). Nonlinear response-history analyses (NRHA) were conducted for each bridge sample using a detailed 3-D analytical model subjected to earthquake ground motions of varying seismic intensities. A component-based approach that uses several engineering demand parameters was employed to determine the seismic response of critical bridge components. Corresponding damage limit states were defined either in terms of member capacities or excessive bearing displacements. Lognormal fragility curves were obtained by curve fitting the point estimates of the probability of exceeding each specified damage limit state for each major bridge class. Bridges with larger skew angles or single-column bents were found to be the most seismically vulnerable.

Hazard Disaggregation and Record Selection for Fragility Analysis and Earthquake Loss Estimation

2017 ◽  
Vol 33 (2) ◽  
pp. 529-549 ◽  
Author(s):  
Luis Sousa ◽  
Mário Marques ◽  
Vitor Silva ◽  
Humberto Varum
Keyword(s):  
Ground Motion ◽  
Limit State ◽  
Fragility Analysis ◽  
Economic Losses ◽  
Earthquake Risk ◽  
Structural Class ◽  
Ground Motion Selection ◽  
Record Selection ◽  
Hazard Disaggregation ◽  
The Impact

Economic losses and collapse probability are critical measures for evaluating the earthquake risk of existing buildings. In this context, this study sheds light on several problems and limitations in current practice of hazard-consistent ground-motion selection and fragility analysis, focusing on the impact that (commonly assumed) approximations in disaggregation outputs have on the aforementioned risk metrics, as opposed to an exact solution. These issues are investigated for several building classes, seismicity models and ground motion prediction equations (GMPE), for a site in the city of Lisbon (Portugal). It is observed that only an exact (i.e., rupture-by-rupture) disaggregation can lead to satisfactory results in terms of accuracy, when limit state criteria are not structure-specific. On the other hand, an approximate method is proposed, which still leads to statistically valid results regardless of the chosen structural class, seismicity model or GMPE.

scholarly journals Reliability-based design of internal limit states for mechanically stabilized earth walls using geosynthetic reinforcement

2019 ◽  
Vol 56 (6) ◽  
pp. 774-788 ◽  
Author(s):  
Richard J. Bathurst ◽  
Peiyuan Lin ◽  
Tony Allen
Keyword(s):  
Reliability Index ◽  
Limit State ◽  
Closed Form Solution ◽  
Form Solution ◽  
Design Practice ◽  
Mechanically Stabilized Earth ◽  
Limit States ◽  
Reliability Based Design ◽  
Mechanically Stabilized

This paper demonstrates reliability-based design for tensile rupture and pullout limit states for mechanically stabilized earth (MSE) walls constructed with geosynthetic (geogrid) reinforcement. The general approach considers the accuracy of the load and resistance models that appear in each limit state equation plus uncertainty due to the confidence (level of understanding) of the designer at the time of design. The reliability index is computed using a closed-form solution that is easily implemented in a spreadsheet. The general approach provides a quantitative link between nominal factor of safety, which is familiar in allowable stress design practice, and reliability index used in modern civil engineering reliability-based design practice. A well-documented MSE wall case study is used to demonstrate the general approach and to compare margins of safety using different load and resistance model combinations. A practical outcome from the case study example is the observation that the pullout limit state is much less likely to control design than the ultimate tensile rupture state for walls with continuous reinforcement coverage. The more accurate “simplified stiffness method” that is used to compute tensile loads in the reinforcement under operational conditions is shown to generate a more cost-effective reinforcement option than the less accurate American Association of State Highway and Transportation Officials (AASHTO) simplified method.

Using the Conditional Spectrum Method for Improved Fragility Assessment of Concrete Gravity Dams in Eastern Canada

2016 ◽  
Vol 32 (3) ◽  
pp. 1449-1468 ◽  
Author(s):  
Carl Bernier ◽  
Ricardo Monteiro ◽  
Patrick Paultre
Keyword(s):  
Fragility Curves ◽  
Ground Motions ◽  
Accurate Estimation ◽  
Gravity Dams ◽  
Eastern Canada ◽  
Proper Selection ◽  
Concrete Gravity Dams ◽  
Target Spectrum ◽  
Ground Motion Records ◽  
Selection Of

The accurate estimation of fragility functions requires the proper selection of ground motion records at different intensity levels. However, most of the available fragility assessments of concrete dams use the same records at all intensity levels and often selects them with an inadequate target spectrum. In order to improve the fragility assessment of such structures, this paper proposes the use of records selected with the Conditional Spectrum (CS) method within a multiple stripes analysis. The approach is applied to a dam in Eastern Canada, and a comparison with the methodology used by other studies is done. It is shown that the approach proposed herein allows for the reduction of the seismic response and fragility of the dam. Moreover, the uncertainty related to material properties becomes less significant when using the CS method, and the fragility curves could be reasonably estimated by considering the ground motions as the only source of uncertainty.

Fragility analysis of self-centering prestressed concrete bridge pier with external aluminum dissipators

2016 ◽  
Vol 20 (8) ◽  
pp. 1210-1222 ◽  
Author(s):  
Zhiliang Cao ◽  
Hao Wang ◽  
Tong Guo
Keyword(s):  
Reinforced Concrete ◽  
Prestressed Concrete ◽  
Fragility Curves ◽  
Limit State ◽  
Seismic Capacity ◽  
External Energy ◽  
Limit States ◽  
Performance Limit ◽  
Residual Drift ◽  
Capacity Evaluation

A novel self-centering prestressed concrete pier with external energy dissipators has been developed to realize seismic resilient performance and enhanced corrosion-resisting property. Self-centering capacity of the pier is provided by the unbonded post-tensioned tendons and damage is mostly concentrated on the replaceable dissipators. To investigate the seismic behavior of the proposed pier, a detailed analytical model considering interface opening and dissipator deformation was developed and verified through existing cyclic load tests. Based on the proposed model, a prototype reinforced concrete pier and a self-centering prestressed concrete pier with similar backbone curves are designed, and fragility analyses are conducted on the two piers through incremental dynamic analysis. One maximum drift-based performance limit state (i.e. collapse prevention) and two residual drift-based performance limit states (i.e. emergent usage and reconstruction) are defined for seismic capacity evaluation. Fragility curves indicate that the self-centering prestressed concrete pier has a slightly higher peak drift demand owing to its inferior dissipating capacity as compared with the reinforced concrete pier, while sustains a much lower residual drift demand due to its inherent self-centering characteristic.

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