Enhanced Seismic Fragility Analysis of Unanchored Steel Storage Tanks Accounting for Uncertain Modeling Parameters

2018 ◽  
Vol 141 (1) ◽  
Author(s):  
Hoang Nam Phan ◽  
Fabrizio Paolacci ◽  
Silvia Alessandri
Keyword(s):  
Seismic Vulnerability ◽  
Failure Modes ◽  
Fragility Curves ◽  
Pushover Analysis ◽  
Sampling Procedure ◽  
Fractional Factorial ◽  
Fragility Analysis ◽  
Seismic Fragility ◽  
Bottom Plate ◽  
Storage Tanks

Catastrophic failure of the above ground steel storage tanks was observed during past earthquakes, which caused serious economic and environmental consequences. Many of the existing tanks were designed in the past with outdated analysis methods and with underestimated seismic loads. Therefore, the evaluation of the seismic vulnerability of these tanks, especially ones located in seismic prone areas, is extremely important. Seismic fragility functions are useful tools to quantify the seismic vulnerability of structures in the framework of probabilistic seismic risk assessment. These functions give the probability that a seismic demand on a given structural component meets or exceeds its capacity. The objective of this study is to examine the seismic vulnerability of an unanchored steel storage tank, considering the uncertainty of modeling parameters that are related to material and geometric properties of the tank. The significance of uncertain modeling parameters is first investigated with a screening study, which is based on nonlinear static pushover analyses of the tank using the abaqus software. In this respect, a fractional factorial design and an analysis of variance (ANOVA) have been adopted. The results indicate that the considered modeling parameters have significant effects on the uplift behavior of the tank. The fragility curves of two critical failure modes, i.e., the buckling of the shell plate and the plastic rotation of the shell-to-bottom plate joint, are then developed based on a simplified model of the tank, where the uplift behavior is correctly modeled from the static pushover analysis. The uncertainty associated with the significant parameters previously identified are considered in the fragility analysis using a sampling procedure to generate statistically significant samples of the model. The relative importance of different treatment levels of the uncertainty on the fragility curves of the tank is assessed and discussed in detail.

Enhanced Seismic Fragility Analysis of Unanchored Above-Ground Steel Liquid Storage Tanks

2018 ◽  
Author(s):  
Hoang Nam Phan ◽  
Fabrizio Paolacci ◽  
Silvia Alessandri ◽  
Phuong Hoa Hoang
Keyword(s):  
Fragility Curves ◽  
Pushover Analysis ◽  
Sampling Procedure ◽  
Fragility Analysis ◽  
Storage Tanks ◽  
Lumped Mass ◽  
Mass Model ◽  
Ground Shaking ◽  
Oil Storage ◽  
Processing Plants

Earthquake damage in recent decades has revealed that storage tanks are one of the most vulnerable components in petrochemical and oil processing plants. Damage to tanks commonly associated with losses of containment, and thus results in the overall damage to nearby areas. Many of existing steel storage tanks were designed with outdated analysis methods and with underestimated seismic loads; therefore, various types of failure may occur during a strong ground shaking. This paper aims to present an appropriate methodology for the component fragility evaluation of existing storage tanks in a process plant, which will support for the determination of the loss of containment in terms of the ground motion intensity measure and finally the quantitative risk analysis of the plant and its nearby areas. In this respect, an unanchored oil storage tank, which is ideally located in Sicily (Italy), is selected as a case study. The significance of modeling parameters of the tank is first investigated with a screening study, which is based on nonlinear static pushover analyses of the tank using the ABAQUS software. The study aims to enhance the understanding of which modeling parameters significantly affect the seismic response of the tank and to reduce the number of analyses in the fragility evaluation. The fragility curves are then developed based on a lumped-mass model that is calibrated from the static pushover analysis results. Sources of uncertainty, related to significant parameters previously identified, are considered in the fragility analysis using a sampling procedure to generate statistically significant samples of the model.

scholarly journals Vulnerability Analysis of Ancient Timber Architecture by Considering the Correlation of Different Failure Modes

2018 ◽  
Vol 2018 ◽  
pp. 1-10 ◽  
Author(s):  
Junhong Huan ◽  
Donghui Ma ◽  
Wei Wang
Keyword(s):  
Ming Dynasty ◽  
Seismic Vulnerability ◽  
Failure Modes ◽  
Fragility Curves ◽  
Lower Boundary ◽  
Seismic Fragility ◽  
Occurrence Probability ◽  
Joint Distribution Function ◽  
First Order ◽  
Innovative Method

The paper proposes an innovative method of analyzing the seismic fragility of ancient timber architecture. The method is based on the Copulas, in which correlation between different failure modes is considered. This method is applied to assess the vulnerability of ancient timber architecture in Ming dynasty. The assessment includes four steps. In the first step, the incremental dynamic analysis is employed to establish seismic vulnerability curves of different failure modes for the structure. After that, Copula joint distribution function is used to analyze the correlation among different failure modes. In the third step, fragility curves considering correlation among different failure modes are established. In the last step, the fragility curves are compared with those obtained by first-order bound method. The results show that seismic vulnerability of ancient timber architecture based on the Copulas is greater than that of any single failure modes. Moreover, the occurrence probability ranges between the upper and lower boundaries of the first-order bound method, but is close to the lower boundary.

scholarly journals Seismic Fragility Assessment of Steel Liquid Storage Tanks

2015 ◽  
Author(s):  
Konstantinos Bakalis ◽  
Dimitrios Vamvatsikos ◽  
Michalis Fragiadakis
Keyword(s):  
Failure Modes ◽  
Fragility Curves ◽  
Seismic Fragility ◽  
Assessment Procedure ◽  
Storage Tanks ◽  
Component Level ◽  
Damage State ◽  
Liquid Storage ◽  
Damage States ◽  
Buckling Failure

A seismic fragility assessment procedure is developed for atmospheric steel liquid storage tanks. Appropriate system and component-level damage states are defined by identifying the failure modes that may occur during a strong ground motion. Special attention is paid to the elephant’s foot buckling failure mode, where the estimation of the associated capacity and demand requires thorough consideration within a probabilistic framework. A novel damage state is introduced to existing procedures with respect to the uncontrollable loss of containment scenario. Fragility curves are estimated by introducing both aleatory and epistemic sources of uncertainty, thus providing a comprehensive methodology for the seismic risk assessment of liquid storage tanks. The importance of dynamic buckling is acknowledged and the issue of non-sequential damage states is finally revealed.

Sliding Response of Unanchored Steel Storage Tanks Subjected to Seismic Loading

2019 ◽  
Author(s):  
Bledar Kalemi ◽  
Muhammad Farhan ◽  
Daniele Corritore
Keyword(s):  
Seismic Vulnerability ◽  
Failure Modes ◽  
Fragility Curves ◽  
Vertical Component ◽  
Friction Model ◽  
Fe Model ◽  
Storage Tanks ◽  
Damage State ◽  
Industrial Installation ◽  
Critical Components

Abstract Steel storage tanks are critical components of an industrial installation due to their high seismic vulnerability and containment of hazardous materials. Failure of a which, may lead to loss of containment (LOC) triggering domino effects such as explosion, environmental pollution, loss of functionality and disruption of business. Past earthquakes have demonstrated different type of failure modes in steel storage tanks. Although there are plenty of studies related to different failure modes like elephant foot buckling or tank uplifting, there are very few efforts on the sliding behavior of tank. Large displacements caused by the tank sliding can lead to pipe detachment and release of hazardous material which might cause damage propagation. Consequently, this damage state is very important for the Quantitative Seismic Risk Assessment of industrial plants. In order to enumerate the sliding displacement of unanchored steel storage tanks, a simplified numerical model realized with OpenSees platform is proposed. The friction model used in OpenSees is calibrated with the results obtained from ABAQUS FE model. Sliding response of tanks with different D/H ratio is analyzed using the simplified model. Fragility curves for the tank sliding damage state are analytically evaluated for different D/H ratio of the tank using the “cloud method”. Finally, a parametric study is conducted in order to comprehend the influence of different parameters on the sliding behavior such as friction coefficient, tank filling level and the influence of the vertical component of ground motions.

Observational Seismic Fragility Curves for Steel Cylindrical Tanks

2018 ◽  
Vol 141 (1) ◽  
Author(s):  
Marta D'Amico ◽  
Nicola Buratti
Keyword(s):  
Seismic Vulnerability ◽  
Fragility Curves ◽  
Bayesian Regression ◽  
Industrial Safety ◽  
Seismic Fragility ◽  
Storage Tanks ◽  
Ground Acceleration ◽  
Technical Literature ◽  
Cylindrical Tanks ◽  
Extent Of Damage

The evaluation of seismic vulnerability of atmospheric above ground steel storage tanks is a fundamental topic in the context of industrial safety. Depending on the shell portion affected, on the extent of damage, and on toxicity, flammability, and reactivity of stored substances, liquid leakages can trigger hazardous chains of events whose consequences affect not only the plant but also the surrounding environment. In light of that, the study proposed herein provides an analysis of the seismic fragility of cylindrical above ground storage tanks based on observational damage data. The first phase of this work has consisted in collecting a large empirical dataset of information on failures of atmospheric tanks during past earthquakes. Two sets of damage states have then been used in order to characterize the severity of damage and the intensity of liquid releases. Empirical fragility curves have been fitted by using Bayesian regression. The advantage of this approach is that it is well suited to treat direct and indirect information obtained from field observations and to incorporate subjective engineering judgement. Different models have been employed in order to investigate the effects of tank aspect ratio, filling level, and base anchorage. Moreover, the effects of interaction between these critical aspects are included in fragility analysis. The hazard parameter used is the peak ground acceleration (PGA). Seismic fragility curves obtained from the described procedure are compared to those available in the technical literature.

Comparison of steel frames with RWS and WFP beam-to-column connections through seismic fragility analysis

2020 ◽  
pp. 136943322097728
Author(s):  
Haoran Yu ◽  
Weibin Li
Keyword(s):  
Limit State ◽  
Pushover Analysis ◽  
Steel Frames ◽  
Fragility Analysis ◽  
Structural Safety ◽  
Seismic Fragility ◽  
Fe Modelling ◽  
Collapse Resistance ◽  
Seismic Collapse ◽  
Probabilistic Seismic Demand

Reduced web section (RWS) connections and welded flange plate (WFP) connections can both effectively improve the seismic performance of a structure by moving plastic hinges to a predetermined location away from the column face. In this paper, two kinds of steel frames—with RWS connections and WFP connections—as well as different frames with welded unreinforced flange connections were studied through seismic fragility analysis. The numerical simulation was conducted by using multiscale FE modelling. Based on the incremental dynamic analysis and pushover analysis methods, probabilistic seismic demand analysis and seismic capability analysis were carried out, respectively. Finally, combined with the above analysis results, probabilistic seismic fragility analysis was conducted on the frame models. The results showed that the RWS connection and WFP connection (without double plates) have little influence on reducing the maximum inter-storey drift ratio under earthquake action. RWS connections slightly reduce the seismic capability in non-collapse stages and improve the seismic collapse resistance of a structure, which exhibits good structural ductility. WFP connections can comprehensively improve the seismic capability of a structure, but the seismic collapse resistance is worse than that of RWS connections when the structure has a large number of storeys. The frame with WFP connections has a lower failure probability at every seismic limit state, while the frame with RWS connections sacrifices some of its structural safety in non-collapse stages to reduce the collapse probability.

Vulnerability-Based Design of Sliding Concave Bearings for the Seismic Isolation of Steel Storage Tanks

2016 ◽  
Author(s):  
Hoang Nam Phan ◽  
Fabrizio Paolacci ◽  
Silvia Alessandri ◽  
Phuong Hoa Hoang
Keyword(s):  
Liquid Steel ◽  
Seismic Isolation ◽  
Failure Modes ◽  
Fragility Curves ◽  
Time History ◽  
Probability Of Failure ◽  
Design Parameters ◽  
Economic Losses ◽  
Storage Tanks ◽  
Isolation System

Liquid steel storage tanks are strategic structures for industrial facilities and have been widely used both in nuclear and non-nuclear power plants. Typical damage to tanks occurred during past earthquakes such as cracking at the bottom plate, elastic or elastoplastic buckling of the tank wall, failure of the ground anchorage system, and sloshing damage around the roof, etc. Due to their potential and substantial economic losses as well as environmental hazards, implementations of seismic isolation and energy dissipation systems have been recently extended to liquid storage tanks. Although the benefits of seismic isolation systems have been well known in reducing seismic demands of tanks; however, these benefits have been rarely investigated in literature in terms of reduction in the probability of failure. In this paper, A vulnerability-based design approach of a sliding concave bearing system for an existing elevated liquid steel storage tank is presented by evaluating the probability of exceeding specific limit states. Firstly, nonlinear time history analyses of a three-dimensional stick model for the examined case study are performed using a set of ground motion records. Fragility curves of different failure modes of the tank are then obtained by the well-known cloud method. In the following, a seismic isolation system based on concave sliding bearings is proposed. The effectiveness of the isolation system in mitigating the seismic response of the tank is investigated by means of fragility curves. Finally, an optimization of design parameters for sliding concave bearings is determined based on the reduction of the tank vulnerability or the probability of failure.

scholarly journals Seismic Fragility Analysis of Mid-Story Isolation Buildings

2021 ◽  
Keyword(s):  
Fragility Curves ◽  
Ground Motions ◽  
Near Field ◽  
Fragility Analysis ◽  
Seismic Fragility ◽  
Plastic State ◽  
Far Field ◽  
Analysis Method ◽  
Isolation System ◽  
Isolation Layer

Abstract. Seismic fragility analysis is essential for seismic risk assessment of structures. This study focuses on the damage probability assessment of the mid-story isolation buildings with different locations of the isolation system. To this end, the performance-based fragility analysis method of the mid-story isolation system is proposed, adopting the maximum story drifts of structures above and below the isolation layer and displacement of the isolation layer as performance indicators. Then, the entire process of the mid-story isolation system, from the initial elastic state to the elastic-plastic state, then to the limit state, is simulated on the basis of the incremental dynamic analysis method. Seismic fragility curves are obtained for mid-story isolation buildings with different locations of the isolation layer, each with fragility curves for near-field and far-field ground motions, respectively. The results indicate that the seismic fragility probability subjected to the near-field ground motions is much greater than those subjected to the far-field ground motions. In addition, with the increase of the location of the isolation layer, the dominant components for the failure of mid-story isolated structures change from superstructure and isolation system to substructure and isolation system.

Seismic Fragility Analysis of Hill Buildings with Uneven Ground Column Heights

2014 ◽  
Vol 638-640 ◽  
pp. 1848-1853
Author(s):  
Lin Qing Huang ◽  
Li Ping Wang ◽  
Chao Lie Ning
Keyword(s):  
Seismic Vulnerability ◽  
Fragility Curves ◽  
Slope Angle ◽  
Seismic Fragility ◽  
Exceedance Probability ◽  
Considerable Influence ◽  
Analysis Method ◽  
Ground Acceleration ◽  
Mountainous Regions ◽  
The Hill

The hill buildings sited on slopes have been widely constructed in mountainous regions. In order to estimate the seismic vulnerability of the hill buildings with uneven ground column heights under the effect of potential earthquakes, the exceedance probabilities of the hill buildings sited on different angle slopes in peak ground acceleration (PGA) are calculated and compared by using the incremental dynamic analysis method. The fragility curves show the slope angle has considerable influence on the seismic performance. Specifically, the exceedance probability increases with the increasing of the slope angle at the same performance level.

Sign in / Sign up

Export Citation Format

Share Document