Reliability-Based Factors of Safety for Vortex Induced Vibration Fatigue Using Field Measurements

2013 ◽  
Vol 135 (4) ◽  
Author(s):  
Michael Tognarelli ◽  
Emmanuel Fontaine ◽  
Pierre Beynet ◽  
Mikhail Santosa ◽  
Hayden Marcollo
Keyword(s):  
Prediction Models ◽  
Deterministic Model ◽  
State Of The Art ◽  
Limit State ◽  
Field Measurements ◽  
Failure Criteria ◽  
State Function ◽  
Analysis Model ◽  
Vortex Induced Vibration ◽  
Vibration Fatigue

The development of a vortex induced vibration (VIV) fatigue factor of safety (FoS) consistent with state-of-the-art industry design practice is cast within the coherent framework of reliability analysis. The proposed methodology consists of the following steps: (i) define the failure criteria or limit-state function (ii) setup a deterministic analysis model (iii) characterize the uncertainties involved in the problem (iv) propagate the uncertainties through the deterministic model and assess the probability of failure due to VIV fatigue and (v) calculate the FoS required to achieve a given failure probability. The proposed methodology is demonstrated by determining the FoS associated with using state-of-the-art VIV prediction models to attain varying reliability levels (probabilities of failure) in a hypothetical design scenario. Prediction uncertainty is based herein on measured flow and response data for several full-scale drilling risers working in the field. Results indicate that depending on the reliability level required of a particular design, different FoS than those that currently appear in guidance may be appropriate. Results also indicate the sensitivity of the FoS to the riser and prevailing current type, analysis program and input parameters, and accumulation of conservatism in aggregate versus single-event damage predictions.

Reliability-Based Factors of Safety for VIV Fatigue Using Field Measurements

2010 ◽  
Author(s):  
Michael Tognarelli ◽  
Emmanuel Fontaine ◽  
Pierre Beynet ◽  
Mikhail Santosa ◽  
Hayden Marcollo
Keyword(s):  
Prediction Models ◽  
Deterministic Model ◽  
State Of The Art ◽  
Limit State ◽  
Field Measurements ◽  
Failure Criteria ◽  
State Function ◽  
Analysis Model ◽  
Measured Flow ◽  
Set Up

The development of a Vortex Induced Vibration (VIV) fatigue Factor of Safety (FoS) consistent with state-of-the-art industry design practice is cast within the coherent framework of reliability analysis. The proposed methodology consists of the following steps: (i) define the failure criteria or limit-state function, (ii) set-up a deterministic analysis model, (iii) characterize the uncertainties involved in the problem, (iv) propagate the uncertainties through the deterministic model and assess the probability of failure due to VIV fatigue and (v) calculate the FoS required to achieve a given failure probability. The proposed methodology is demonstrated by determining the FoS associated with using state-of-the-art VIV prediction models to attain varying reliability levels (probabilities of failure) in a hypothetical design scenario. Prediction uncertainty is based herein on measured flow and response data for several full-scale drilling risers working in the field. Results indicate that depending on the reliability level required of a particular design, different FoS than those that currently appear in guidance may be appropriate. Results also indicate the sensitivity of the FoS to the riser and prevailing current type; analysis program and input parameters; and accumulation of conservatism in aggregate vs. single-event damage predictions.

Advances of a FEM for the Failure Probability Evaluation of Masonry Vehicular Bridge Support Piers

2012 ◽  
Vol 538-541 ◽  
pp. 580-585
Author(s):  
Luis Horacio Martínez-Mártinez ◽  
Gustavo Mendoza-Chavez ◽  
David Joaquin Delgado-Hernandez ◽  
David De León Escobedo ◽  
Elia Mercedes Alonso Guzmán ◽  
...  
Keyword(s):  
Risk Analysis ◽  
Structural Engineering ◽  
Limit State ◽  
Element Model ◽  
Failure Criteria ◽  
Point Of View ◽  
Structural Safety ◽  
State Function ◽  
Limit State Function ◽  
Risk Magnitude

One of the responsibilities of a Civil Engineer is to make decisions regarding preservation of infrastructure; therefore, there have been established concepts such as risk and risk analysis. Risk analysis, is a methodology applied to determine and evaluate the risk magnitude. From the structural engineering point of view, it is required that any structure become secure, this means that the capacity to withstand external actions (strength) will be higher than these actions (loads). In order to determine the structural safety, it is required to define the failure of the structure that it is not strongly related with the collapse of the structure; the failure criteria needs to be fixed depending on the use of the building and the consequences associated with the interruption of services provided by the facility. The failure then, is calculated by means of a limit state function in where it is established the failure criteria; failure is reached when a specific condition (strength) is surpassed by the actions over the structure. The present work aims to propose a preliminary Finite Element Model (FEM) that represents a pier used as support for vehicular bridges. This FEM is required for the assessment of mechanical behavior of the structure that will be used for the determination of the limit state function needed for risk assessment. Most of the simulations with FEM presented in literature are very used for modeling of masonry walls, but it is not usual to model structures such as bridge piers.

scholarly journals An Overview of Engineering Concepts and Current Design Algorithms for Probabilistic Structural Analysis

1995 ◽  
Author(s):  
S. F. Duffy ◽  
J. Hu ◽  
D. A. Hopkins
Keyword(s):  
Failure Analysis ◽  
Limit State ◽  
Failure Criteria ◽  
Initial Section ◽  
State Function ◽  
Probabilistic Design ◽  
Weibull Analysis ◽  
Initial Portion ◽  
Design Philosophy ◽  
Probabilistic Failure Analysis

Abstract The article begins by examining the fundamentals of traditional deterministic design philosophy. The initial section outlines the concepts of failure criteria and limit state functions, two traditional notions that are embedded in deterministic design philosophy. This is followed by a discussion regarding safety factors (a possible limit state function) and the common utilization of statistical concepts in deterministic engineering design approaches. Next, the fundamental aspects of a probabilistic failure analysis are explored, and it is shown that deterministic design concepts mentioned in the initial portion of the article are embedded in probabilistic design methods. For components fabricated from ceramic materials (and other similarly brittle materials) the probabilistic design approach yields the widely used Weibull analysis after suitable assumptions are incorporated. The authors point out that Weibull analysis provides the rare instance where closed form solutions are available for a probabilistic failure analysis. Since numerical methods are usually required to evaluate component reliabilities, a section on Monte Carlo methods is included to introduce the concept. The article concludes with a presentation of the technical aspects that support the numerical method known as fast probability integration (FPI). This includes a discussion of the Hasofer-Lind and Rackwitz-Fiessler approximations.

scholarly journals Study of stability against deep sliding of gravity dam based on JC method

2018 ◽  
Vol 38 ◽  
pp. 03045
Author(s):  
Zheng Si ◽  
Lanfang Xin ◽  
Lingzhi Huang ◽  
Zhengxin Wang
Keyword(s):  
Rigid Body ◽  
Limit Equilibrium ◽  
Limit State ◽  
Limit Equilibrium Method ◽  
Gravity Dam ◽  
State Function ◽  
Analysis Model ◽  
Gravity Dams ◽  
Equilibrium Method ◽  
The Stability

In this study, stability against deep sliding of gravity dam is analysed in order to provide guidance for ensuring stability against sliding of gravity dam during the construction and operation periods. Based on checking-point method (JC method), the study proposes an analysis model for stability against deep sliding of gravity dams. In addition, the rigid body limit equilibrium method is utilized to construct the limit state function of deep anti-sliding stability. With sliding plane anti-shear friction coefficient and anti-shear cohesion calculated as random variables, safety degree of stability against deep sliding is analysed. With JC method employed, the calculation program is compiled to calculate the stability against deep sliding of gravity dam and analyse the non-overflow section of gravity dam under normal storage level. According to calculation program, the reliability index β of stability against deep sliding of gravity dam is 4.36, and the failure risk Pf is approximately zero. Additionally, based on the traditional rigid body limit equilibrium method, the safety factor K is 3.23, which meets the requirements of the design specification. According to the above methods, stability against deep sliding of the dam section meets the requirement. In conclusion, JC method provides a calculation and analysis model for gravity dam’s stability against deep sliding, serving as references in the design of gravity dams based on reliability theory.

A Practical Drilling Riser and Wellhead Vortex Induced Vibration Fatigue Comparison Between Analysis and Field Measured Data

2015 ◽  
Author(s):  
Michael Long Ge ◽  
Jomon Kannala ◽  
David Cain ◽  
Elizbar B. Kebadze ◽  
Shankar Sundararaman ◽  
...  
Keyword(s):  
Fatigue Damage ◽  
Field Measurements ◽  
Current Data ◽  
Loop Current ◽  
Vortex Induced Vibration ◽  
Acceleration Data ◽  
Blowout Preventer ◽  
Vibration Fatigue ◽  
Industry Practice ◽  
Analytical Tools

In order to design a drilling riser system that meets the operational requirements, it is industry practice to use analytical tools to predict the riser and wellhead fatigue damage. This paper focuses on the comparison between the analysis and field measurements for both the drilling riser and wellhead vortex induced vibration (VIV) fatigue damage, during a recent loop current event in the Gulf of Mexico. The field data, which includes the drilling riser configuration, riser tensioner setting, and loop current data, were considered in this comparison. As one of the key contributors to VIV fatigue, the loop current, was measured from a survey vessel in the field during the blowout preventer (BOP) latched and retrieval period. The analysis utilized the VIV program SHEAR7 V4.6 to calculate the fatigue damage for both the drilling riser and wellhead system. The field measured acceleration data from the installed monitoring system was converted to the fatigue damage by transfer function methods. Key findings and conclusions are summarized to improve future analysis predictions of drilling riser and wellhead fatigue damage.

Non-Probabilistic Reliability of RC Bridge Retrofitted in Flexure with Externally Bonded Steel Plates

2013 ◽  
Vol 351-352 ◽  
pp. 1590-1595
Author(s):  
Shi Jun Li ◽  
Xu Yong Chen
Keyword(s):  
Reliability Analysis ◽  
Convex Sets ◽  
Limit State ◽  
Steel Plates ◽  
Small Samples ◽  
Sufficient Information ◽  
State Function ◽  
Uncertain Parameters ◽  
Analysis Model ◽  
Convex Model

Sufficient information about uncertain parameters is unavailable and very costly in the conventional reliability analysis of the retrofitted RC bridge. The non-probabilistic convex set only requires small samples to obtain the variation bounds of uncertain parameters. An interval set denotes the variation range of an uncertain parameter, and two convex sets reflect the relationships of uncertainty parameters. The non-probabilistic reliability analysis model is developed based on limit-state function and convex model. The non-probabilistic reliability index is solved by the gradient projection method. The engineering example shows that the non-probabilistic reliability is reasonable and economical, and perfects the method and theory of reliability analysis for the retrofitted BC bridge.

Structural Non-Probabilistic Reliability Analysis Based on Imperialist Competitive Algorithm

2013 ◽  
Vol 712-715 ◽  
pp. 1501-1505
Author(s):  
Yan Hao ◽  
Guang Wei Meng ◽  
Feng Li ◽  
Li Ming Zhou
Keyword(s):  
Reliability Analysis ◽  
Optimization Problems ◽  
Limit State ◽  
Imperialist Competitive Algorithm ◽  
Global Optimum ◽  
State Function ◽  
Penalty Function Method ◽  
Analysis Model ◽  
Competitive Algorithm ◽  
Optimum Solution

A structural non-probabilistic reliability analysis model based on the imperialist competitive algorithm (ICA) is proposed. In practical engineering, the independent variables of the limit state function are usually the structural responses, which, together with the gradients, need to be resolved. The proposed model could find out the global optimum solution through the competition among the empires, without any additional gradient information, showing a good feasibility in many kinds of optimization problems. When utilizing the penalty function method, the constraint domain is enlarged to the failure domain, overcome the difficulties of searching the optimum due to the former narrower constraint domain. A numerical example verifies the high precision and good feasibility of the model.

Reliability Analysis of Asphalt Pavement Structure Based on Three-Dimensional Finite Element

2011 ◽  
Vol 255-260 ◽  
pp. 3421-3425
Author(s):  
Shi Bin Ma ◽  
Kai Wang ◽  
Yang Feng Wu ◽  
Lian Yu Wei ◽  
Ming Wei Zhang
Keyword(s):  
Reliability Analysis ◽  
Asphalt Pavement ◽  
Limit State ◽  
Three Dimensional ◽  
Latin Hypercube Sampling ◽  
Failure Criteria ◽  
Design Parameters ◽  
State Function ◽  
Element Analysis ◽  
Pavement Structure

The design of asphalt pavements in china is currently based on the multilayered elastic method, which is analytical in nature and yields stresses, strains, and deflections in the pavement system for a particular loading condition and pavement geometry, which are compared with established failure criteria to determine the performance of the given pavement. This design approaches is deterministic. In this paper, typical asphalt pavement structure reliability analysis was performed in which factors that affect pavement reliability regarded as input random , pavement surface deflection, layers of bottom stress and limit state function regarded as output variables , by reliability tool infinite element analysis, base on Monte Carlo’s Latin hypercube sampling method.At last the paper pertinently offered decision basis for improve the reliability of pavement structure and important reference values for drafting and selecting of asphalt pavement design parameters through calculating the reliability of pavement structure, sensitivity analysis of the design parameters is made.

Reliability and reliability-based sensitivity analysis of self-centering buckling restrained braces using meta-models

2021 ◽  
pp. 1045389X2110263
Author(s):  
Seyede Vahide Hashemi ◽  
Mahmoud Miri ◽  
Mohsen Rashki ◽  
Sadegh Etedali
Keyword(s):  
Failure Probability ◽  
Limit State ◽  
Computational Cost ◽  
Sensitivity Analyses ◽  
State Function ◽  
Reliability Indices ◽  
Buckling Restrained Brace ◽  
Polynomial Response Surface ◽  
Nonlinear Dynamic Analyses ◽  
High Computational Cost

This paper aims to carry out sensitivity analyses to study how the effect of each design variable on the performance of self-centering buckling restrained brace (SC-BRB) and the corresponding buckling restrained brace (BRB) without shape memory alloy (SMA) rods. Furthermore, the reliability analyses of BRB and SC-BRB are performed in this study. Considering the high computational cost of the simulation methods, three Meta-models including the Kriging, radial basis function (RBF), and polynomial response surface (PRSM) are utilized to construct the surrogate models. For this aim, the nonlinear dynamic analyses are conducted on both BRB and SC-BRB by using OpenSees software. The results showed that the SMA area, SMA length ratio, and BRB core area have the most effect on the failure probability of SC-BRB. It is concluded that Kriging-based Monte Carlo Simulation (MCS) gives the best performance to estimate the limit state function (LSF) of BRB and SC-BRB in the reliability analysis procedures. Considering the effects of changing the maximum cyclic loading on the failure probability computation and comparison of the failure probability for different LSFs, it is also found that the reliability indices of SC-BRB were always higher than the corresponding reliability indices determined for BRB which confirms the performance superiority of SC-BRB than BRB.

scholarly journals Critical Aspects of Person Counting and Density Estimation

2021 ◽  
Vol 7 (2) ◽  
pp. 21
Author(s):  
Roland Perko ◽  
Manfred Klopschitz ◽  
Alexander Almer ◽  
Peter M. Roth
Keyword(s):  
Density Estimation ◽  
Network Architecture ◽  
Reference Data ◽  
State Of The Art ◽  
Limit State ◽  
Ground Truth ◽  
Data Sets ◽  
Ground Truth Generation ◽  
Baseline Approach ◽  
Critical Aspects

Many scientific studies deal with person counting and density estimation from single images. Recently, convolutional neural networks (CNNs) have been applied for these tasks. Even though often better results are reported, it is often not clear where the improvements are resulting from, and if the proposed approaches would generalize. Thus, the main goal of this paper was to identify the critical aspects of these tasks and to show how these limit state-of-the-art approaches. Based on these findings, we show how to mitigate these limitations. To this end, we implemented a CNN-based baseline approach, which we extended to deal with identified problems. These include the discovery of bias in the reference data sets, ambiguity in ground truth generation, and mismatching of evaluation metrics w.r.t. the training loss function. The experimental results show that our modifications allow for significantly outperforming the baseline in terms of the accuracy of person counts and density estimation. In this way, we get a deeper understanding of CNN-based person density estimation beyond the network architecture. Furthermore, our insights would allow to advance the field of person density estimation in general by highlighting current limitations in the evaluation protocols.

Sign in / Sign up

Export Citation Format

Share Document