scholarly journals The proposal of explicit account of the random character of design process parameters

2013 ◽  
Vol 12 (1) ◽  
pp. 219-226
Author(s):  
Agnieszka Dudzik ◽  
Urszula Radoń
Keyword(s):  
Structural Design ◽  
Reliability Index ◽  
Research Method ◽  
Sampling Methods ◽  
Limit State ◽  
Random Variables ◽  
Design Parameters ◽  
Structural Failure ◽  
Primary Research ◽  
Random Character

The study concerns the static analysis of rods structures in terms of probabilism. Structural design parameters are defined as the deterministic values and random variables. Random variables are not correlated. The criterion for structural failure is expressed the limits of functions referring to the ultimate and serviceability limit state. The Cornell and Hasofer-Lind index is used as a reliability measure. The primary research method is the FORM method. In order to verify the correctness of the calculation SORM, Monte Carlo and Importance Sampling methods are used. The sensitivity of reliability index to the random variables is defined. The STAND program is used to present the examples of reliability analysis.

scholarly journals The Evaluation Of Algorithms For Determination Of The Reliability Index

2015 ◽  
Vol 61 (3) ◽  
pp. 133-147 ◽  
Author(s):  
A. Dudzik ◽  
U. Radoń
Keyword(s):  
Reliability Index ◽  
Limit State ◽  
Probabilistic Approach ◽  
Random Variables ◽  
Numerical Procedure ◽  
Vertical Displacement ◽  
Design Parameters ◽  
State Function ◽  
Structural Failure

AbstractThe study deals with stability and dynamic problems in bar structures using a probabilistic approach. Structural design parameters are defined as deterministic values and also as random variables, which are not correlated. The criterion of structural failure is expressed by the condition of non-exceeding the admissible load multiplier and condition of non-exceeding the admissible vertical displacement. The Hasofer-Lind index was used as a reliability measure. The primary research tool is the FORM method. In order to verify the correctness of the calculations Monte Carlo and Importance Sampling methods were used. The sensitivity of the reliability index to the random variables was defined. The limit state function is not an explicit function of random variables. This dependence was determined using a numerical procedure, e.g. the finite element methods. The paper aims to present the communication between the STAND reliability analysis program and the KRATA and MES3D external FE programs.

The Comparison of Methods of Assessing the Reliability of the Steel Frame

2015 ◽  
Vol 797 ◽  
pp. 11-18
Author(s):  
Agnieszka Dudzik ◽  
Urszula Radoń
Keyword(s):  
Reliability Index ◽  
Limit State ◽  
Probabilistic Approach ◽  
Random Variables ◽  
Random Variable ◽  
Design Parameters ◽  
Variable Sensitivity ◽  
Index Sensitivity ◽  
The Impact ◽  
The Mathematical Model

The study presents a probabilistic approach to the problems of static analysis of a steel building. Structural design parameters were defined as deterministic values and random variables. The latter were not correlated. The criterion of structural failure is expressed by limit functions related to the ultimate and serviceability limit state. The description of limit functions by the Mathematica program was generated. The Hasofer-Lind index was used as a reliability measure. In the description of random variables were used the normal distribution and, for comparison, different types of probability distribution appropriate to the nature of the variable. Sensitivity of reliability index to the random variables was defined. If the reliability index sensitivity due to the random variable Xi is low when compared with other variables, it can be stated that the impact of this variable on failure probability is small. Therefore, in successive computations it can be treated as a deterministic parameter. Sensitivity analysis leads to simplify the description of the mathematical model, determine the new limit functions and values of the Hasofer-Lind reliability index. The primary research method is the FORM method. In order to verify the correctness of the calculation SORM, Monte Carlo and Importance Sampling methods were used. In the examples of reliability analysis the STAND program was used.

Neural network approach to model the limit state surface for reliability analysis

2003 ◽  
Vol 40 (6) ◽  
pp. 1235-1244 ◽  
Author(s):  
Anthony TC Goh ◽  
Fred H Kulhawy
Keyword(s):  
Neural Network ◽  
Reliability Index ◽  
Structural Reliability ◽  
Limit State ◽  
Random Variables ◽  
First Order Reliability Method ◽  
First Order ◽  
The Neural Network ◽  
Reliability Method ◽  
Geotechnical Structures

Structural reliability methods are often used to evaluate the failure performance of geotechnical structures. A common approach is to use the first-order reliability method. Its popularity results from the mathematical simplicity of the method, since only second moment information (mean and coefficient of variation) on the random variables is required. The probability of failure is then assessed by an index known commonly as the reliability index. One critical aspect in determining the reliability index is the explicit definition of the limit state surface of the system. In a problem involving multi-dimensional random variables, the limit state surface is the boundary separating the safe domain from the "failure" (or lack of serviceability) domain. In many complicated and nonlinear problems where the analyses involve the use of numerical procedures such as the finite element method, this surface may be difficult to determine explicitly in terms of the random variables, and therefore the limit state can only be expressed implicitly rather than in a closed-form solution. It is proposed in this paper to use an artificial intelligence technique known as the back-propagation neural network algorithm to model the limit state surface. First, the failure domain is found through repeated point-by-point numerical analyses with different input values. The neural network is then trained on this set of data. Using the optimal weights of the neural network connections, it is possible to develop a mathematical expression relating the input and output variables that approximates the limit state surface. Some examples are given to illustrate the application and accuracy of the proposed approach.Key words: first-order reliability method, geotechnical structures, limit state surface, neural networks, reliability.

Inversion analysis to determine design parameters for reliability assessment in pavement structures

2014 ◽  
Vol 41 (10) ◽  
pp. 845-855 ◽  
Author(s):  
Sungho Mun
Keyword(s):  
Reliability Index ◽  
Limit State ◽  
Reliability Assessment ◽  
Pavement Performance ◽  
Design Parameters ◽  
State Function ◽  
Limit State Function ◽  
Performance Function ◽  
Pavement Structures ◽  
Inversion Analysis

Reliability assessment has been used to evaluate the performance of pavement structures. However, probabilistic inversion analysis of pavement structure design has not yet been tested to determine the design parameters of the pavement performance function, given a specified reliability index. In this study, a limit state function numerical calculation and the inversion technique of the Nelder–Mead simplex algorithm were used to determine the design parameters for the pavement performance function. The method of moments was used to develop the forward limit state function, which was then compared to Monte Carlo simulations; the comparison indicated good agreement between the two methods. Additionally, several cases were studied to determine the design parameters of the pavement performance function for the reliability index specified in this study. The case studies indicated that the structure number significantly affected the pavement performance function.

scholarly journals The structural reliability analysis using explicit neural state functions

2019 ◽  
Vol 262 ◽  
pp. 10002 ◽  
Author(s):  
Agnieszka Dudzik ◽  
Beata Potrzeszcz-Sut
Keyword(s):  
Reliability Analysis ◽  
Reliability Index ◽  
Structural Reliability ◽  
Limit State ◽  
Random Variables ◽  
Transformation Method ◽  
Stability Loss ◽  
Cross Sectional ◽  
Component Reliability ◽  
State Functions

The present study considers the problems of stability and reliability of spatial truss susceptible to stability loss from the condition of node snapping. In the reliability analysis of structure, uncertain parameters, such us load magnitudes, cross-sectional area, modulus of elasticity are represented by random variables. Random variables are not correlated. The criterion of structural failure is expressed by the condition of non-exceeding the admissible load multiplier. In the performed analyses explicit form of the random variables function were used. To formulate explicit limit state functions the neural networks is used. In the paper only the time independent component reliability analysis problems are considered. The NUMPRESS software, created at the IFTR PAS, was used in the reliability analysis. The Hasofer-Lind index in conjunction with transformation method in the FORM was used as a reliability measure. The primary research method is the FORM method. In order to verify the correctness of the calculation SORM and Monte Carlo methods are used. The values of reliability index for different descriptions of mathematical model of the structure were determined. The sensitivity of reliability index to the random variables is defined.

scholarly journals An Efficient Time-Variant Reliability Analysis Method with Mixed Uncertainties

Algorithms ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 229
Author(s):  
Fangyi Li ◽  
Yufei Yan ◽  
Jianhua Rong ◽  
Houyao Zhu
Keyword(s):  
Reliability Analysis ◽  
Limit State ◽  
Random Variables ◽  
Equivalent Model ◽  
Independent Random Variables ◽  
Problem Analysis ◽  
Analysis Method ◽  
Calculation Algorithm ◽  
Reliability Problem ◽  
Interval Variables

In practical engineering, due to the lack of information, it is impossible to accurately determine the distribution of all variables. Therefore, time-variant reliability problems with both random and interval variables may be encountered. However, this kind of problem usually involves a complex multilevel nested optimization problem, which leads to a substantial computational burden, and it is difficult to meet the requirements of complex engineering problem analysis. This study proposes a decoupling strategy to efficiently analyze the time-variant reliability based on the mixed uncertainty model. The interval variables are treated with independent random variables that are uniformly distributed in their respective intervals. Then the time-variant reliability-equivalent model, containing only random variables, is established, to avoid multi-layer nesting optimization. The stochastic process is first discretized to obtain several static limit state functions at different times. The time-variant reliability problem is changed into the conventional time-invariant system reliability problem. First order reliability analysis method (FORM) is used to analyze the reliability of each time. Thus, an efficient and robust convergence hybrid time-variant reliability calculation algorithm is proposed based on the equivalent model. Finally, numerical examples shows the effectiveness of the proposed method.

scholarly journals Speculation in the cryptocurrency market

2021 ◽  
Vol 1 (1) ◽  
Author(s):  
Paweł Milka
Keyword(s):  
Literature Review ◽  
Research Method ◽  
Listed Companies ◽  
Primary Research ◽  
Stock Indices ◽  
The Subject ◽  
Way Of Thinking ◽  
The Impact

The article analyses the impact of speculation on the cryptocurrency market. In the introduction, the author interprets the meaning of the speculation and a speculator’s way of thinking. The literature review was broken down into two aspects. The first is to analyse the literature on the subject in terms of the cryptocurrency market. The second is an analysis of the sentiment index, which becomes the primary research method. The analysis of the sentiment value shows a high correlation between the impact of sentiment on the value of cryptocurrencies. Further recommendations are to analyse the sentiment with regard to listed companies (Polish and international) and stock indices (including the forex market).  

scholarly journals THE SPECIAL UTILIZATION OF CASTLES IN TOURISM – FESTIVALS IN THE HERITAGE SITES

2018 ◽  
pp. 85-98
Keyword(s):  
Impact Assessment ◽  
Case Studies ◽  
Research Method ◽  
Residential Buildings ◽  
Research Question ◽  
Secondary Data ◽  
Primary Research ◽  
Optimal Form ◽  
Heritage Sites ◽  
Built Heritage

In Hungary, there are a large number of built heritage. Of these, this current research focuses on the castles. Nowadays castles can be filled with many functions, such as schools, common lodging houses, hospitals or residential buildings. The most optimal form of usage is tourism utilization, such as museums, hotels, event venues. Organizing festivals is also a tool for this, it generates revenue for the castle, and makes it widely available to enhance the visibility and acquaintance of the venues. A festival is also intended to suffice the needs of tourists and local people, and these castles provide a suitable scene for this. Thus, the current research aims to present and evaluate the form of utilization of castles in which festivals are organized. The study aims to answer the research question through several case studies, that festivals contribute to the survival of the castles as they generate revenue and create more attractive destinations. To answer this question, a primary research method is needed where interviews with the owners of the venues and the festival directors come to the fore. In addition, the available secondary data are required that numerical support the generated revenue and number of visitors alike. In the end, the research will be carried out where both the utilization of the castles and the festival tourism will be of paramount importance and a joint impact assessment will be implemented.

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