Papers by Keyword: Probability of Failure

Abstract: The paper examines a complex methodology for calculating the slope stability of a tailing storage facility based on comparing the results obtained through deterministic and probabilistic approaches. The analysis is performed in GeoStudio software, based on the limit equilibrium method, and with a probabilistic approach that uses a Monte Carlo simulation to compute a probability distribution of the resulting factor of safety. A slope stability assessment of tailing dam was conducted on the example of Ferrexpo Poltava Mining, and a conclusion was reached about their reliability and safety. The results of the deterministic analysis showed that the calculated factor of safety is by those established in Ukrainian regulatory standards. It has been recognized that the factor of safety is not a consistent measure of risk for tailings dam. Considering the variability inherent in the soil materials of tailings dam is a way to achieve more accurate results. The importance of obtaining a failure probability and a reliability index due to tailing dam stability was highlighted by comparing deterministic and probabilistic approaches.

Abstract: The ship hull construction suffers a decrease in strength performance over its life cycle due to corrosion and fatigue. Therefore, the risk of structural failure also rises during the extended service life if maintenance is not performed properly. The budget, on the other hand, limits these activities. As a result, it is critical for ship owners to plan an optimal maintenance program. The idea of this research is to find the best way to keep the hull's structural integrity due to corrosion. A time dependent corrosion model has been developed for failure prediction purposes, based on the historical data of plate thickness reduction. Failure scenarios are carried out on local, global and fatigue strength. This research adopted a semi-quantitative risk assessment along with reliability analysis to give strategic maintenance planning by lowering the risks that would be encountered. Hence, ensuring uninterrupted service of the ship throughout the service life. Finally, this study will be very useful as reference to establish risk informed program to evaluate the risk level of components of hull that guides to adjust inspection intervals without avoiding safety requirements.

Abstract: As a result of the design and construction of buildings and structures, the level of reliability of the construction structure or construction object as a whole is formed. The reliability specified in the project does not remain constant, but changes over time as a result of the imperfection of the design model of the building, inaccuracies of installation, as well as during the accumulation of defects and damage to the building during its use. Currently, the scope of work related to the assessment of the technical condition of buildings is constantly increasing. This is due not only to the increasing number of operated structures, but also an increase in safety requirements and an increase in the qualitative characteristics of buildings. The article proposes to maintain a unified approach to the inspection of the engineering and technical condition that uses the reliability criterion for the basic structural elements of buildings and structures. In modern conditions, it is important to determine the necessary level of reliability acceptable to economic considerations and meets modern safety requirements. It is important to calculate the numerical threshold values of the categories of the technical condition of building structures to eliminate the subjective approach to the assessment of their technical condition.

Abstract: Modern continuous mills FQM are high-performance technological units that allow you to get products of a wide range. The paper presents the results of the study of the effect of the time of holding the mandrel in the extreme position of the continuous mill FQM (Fine Quality Mill) on the probability of defect formation of surface defects. The problems of сcomputational simulation of the process of continuous rolling of pipes were set and solved. It is established that the increase in the holding time of the mandrel allows to reduce the sliding of the metal on the surface of the tool, and contributes to a stable process of removing the mandrel without the formation of defects on the inner surface of the draft pipe. The results of solving the problems of сcomputational modeling allowed to formulate technical recommendations aimed at reducing the probability of surface defects in the production of pipes at the FQM mill.

Abstract: In this paper, the Reliability Analysis with utilizing a Monte Carlo simulation (MCS) process was conducted on the equation of the collapse potential predicted by ANN to study its reliability when utilized in a situation of soil that has uncertainty in its properties. The prediction equation utilized in this study was developed previously by the authors. The probabilities of failure were then plotted against a range of uncertainties expressed in terms of coefficient of variation. As a result of reliability analysis, it was found that the collapse potential equation showed a high degree of reliability in case of uncertainty in gypseous sandy soil properties within the specified coefficient of variation (COV) for each property. When the COV ranges (0-100) for each soil properties under study, it was found also that the collapse potential equation is very well in predicting the collapse potential of gypseous sandy soils for all values of the COV lies between (0-100) % for initial water content and degree of saturation, and for values of the COV not exceed 11%, 19% for the initial dry unit weight and specific gravity respectively, as well as for the values of the COV not exceed 80%, 97% for the initial voids ratio and gypsum content respectively.

Abstract: This study presents the results of a new approach for structural reliability analyses using adaptive kriging, confirmation simulation, and the pilot point method. Its main objective is to develop an efficient and accurate global approximation while controlling the computational cost and accuracy of prediction. The main contribution of research is to reduce computation time and successfully analyze complex problems with accurate results while ensuring excellent predictive quality of the approximation. For an excellent predictability of the kriging approximation, pilot point method and confirmation simulation are proposed. Simply, the predictive quality of the initial kriging approximation is improved by adding adaptive information, and the points are referred to as “pilot points” in areas where the kriging variance is maximized. Outcomes are confirmed with numerical simulations. The purpose is to select the minimum number of design experiments to ensure a good relative accuracy of the predictors with respect to the original models. Numerical examples show the efficiency of the proposed method compared to other structural reliability approaches.

Abstract: Reliability analysis is one of important parameter to ensure the safety of structure during its life time. Especially for large structure which has a high consequences. Conventional method is unable to give an accurate reliability result for a complex structure. Here is presented how MCFEM work to do reliability analysis of complex structure i.e. APN-A Offshore Jacket. Simulation was carried out until 100,000 number of cycles and obtained the reliability of APN-A offshore jacket i.e. 0.8806.

Abstract: It is shown that alternative procedures for probabilistic assessment of design impact forces given in EN 1991-1-7 leads to similar results. The impact forces are up to three times greater than the recommended indicative values given in the main text of EN 1991-1-7. Provided that no other safety measures are undertaken, the structures designed for recommended lower bound of impact forces may have insufficient reliability. Application of the upper limit of impact forces should be recommended for key bridges where the bridge columns are situated near road intersections or in the adverse configuration of the terrain.

Abstract: The Direct Optimized Probabilistic Calculation (DOProC) is originally developed as one way of solving probabilistic problems which don't use any simulation technique. DOProC is based on general terms and procedures used in probabilistic theories. Input random quantities (such as the load, geometry, material properties, or imperfections) are in DOProC method expressed by the parametric or empirical distribution in histograms. DOProC applications are processed in ProbCalc software, in which the calculation model under analysis can be expressed analytically as a sign arithmetic expression or can be expressed using code from the dynamic library. The method requires high-performing information systems for complex tasks. Therefore, efforts have been made to optimize calculations in order to reduce the number of operations, keeping, at the same time, reliable calculation results. The paper will also focus on other special software applications that are able to assess the reliability of bearing structures with respect to fatigue damage or underground works with anchors.

Abstract: Journal fluid bearings are widely used in industry due to their static and dynamic behavior and their very low coefficient of friction. The technical requirements to improve the new technologies design are increasingly focused on the indicators of dependability of systems and machines. Then, it is necessary to develop a methodology to study the reliability of bearings in order to improve and to evaluate their design quality. Few works are referenced in literature concerning the estimation of the reliability of fluid journal bearings. This paper deals with a methodology to study the failure probability of a hydrodynamic journal bearing. An analytical approach is proposed to calculate static characteristics in using the Reynolds equation. The commonly methods used in structural reliability such as FORM (First Order Reliability Method), SORM (Second Order Reliability Method) and Monte Carlo are developed to estimate the failure probability. The function of performance bounding two domains (domain of safety and domain of failure) is estimated for several geometrical configurations of a hydrodynamic journal bearing (long journal bearings with the hypotheses of Sommerfeld, Gümbel and Reynolds, and a short journal bearing with the hypothesis of Gümbel).