Nonlinear finite-element-based structural system failure probability analysis methodology for gravity dams considering correlated failure modes

The structural system failure probability(SFP) is a valuable tool for evaluating the global safety level of concrete gravity dams.Traditional methods for estimating the failure probabilities are based on defined mathematical descriptions,namely,limit state functions of failure modes.Several problems are to be solved in the use of traditional methods for gravity dams.One is how to define the limit state function really reflecting the mechanical mechanism of the failure mode;another is how to understand the relationship among failure modes and enable the probability of the whole structure to be determined.Performing SFP analysis for a gravity dam system is a challenging task.This work proposes a novel nonlinear finite-element-based SFP analysis method for gravity dams.Firstly,reasonable nonlinear constitutive modes for dam concrete,concrete/rock interface and rock foundation are respectively introduced according to corresponding mechanical mechanisms.Meanwhile the response surface(RS) method is used to model limit state functions of main failure modes through the Monte Carlo(MC) simulation results of the dam-interface-foundation interaction finite element(FE) analysis.Secondly,a numerical SFP method is studied to compute the probabilities of several failure modes efficiently by simple matrix integration operations.Then,the nonlinear FE-based SFP analysis methodology for gravity dams considering correlated failure modes with the additional sensitivity analysis is proposed.Finally,a comprehensive computational platform for interfacing the proposed method with the open source FE code Code Aster is developed via a freely available MATLAB software tool(FERUM).This methodology is demonstrated by a case study of an existing gravity dam analysis,in which the dominant failure modes are identified,and the corresponding performance functions are established.Then,the dam failure probability of the structural system is obtained by the proposed method considering the correlation relationship of main failure modes on the basis of the mechanical mechanism analysis with the MC-FE simulations.

System failure analysis based on DEMATEL–ISM and FMECA

A new method of system failure analysis was proposed. First, considering the relationships between the failure subsystems,the decision making trial and evaluation laboratory(DEMATEL) method was used to calculate the degree of correlation between the failure subsystems, analyze the combined effect of related failures, and obtain the degree of correlation by using the directed graph and matrix operations. Then, the interpretative structural modeling(ISM) method was combined to intuitively show the logical relationship of many failure subsystems and their influences on each other by using multilevel hierarchical structure model and obtaining the critical subsystems. Finally, failure mode effects and criticality analysis(FMECA) was used to perform a qualitative hazard analysis of critical subsystems, determine the critical failure mode, and clarify the direction of reliability improvement.Through an example, the result demonstrates that the proposed method can be efficiently applied to system failure analysis problems.

Methodology for estimating probability of dynamical system's failure for concrete gravity dam

Methodology for the reliability analysis of hydraulic gravity dam is the key technology in current hydropower construction.Reliability analysis for the dynamical dam safety should be divided into two phases:failure mode identification and the calculation of the failure probability.Both of them are studied based on the mathematical statistics and structure reliability theory considering two kinds of uncertainty characters(earthquake variability and material randomness).Firstly,failure mode identification method is established based on the dynamical limit state system and verified through example of Koyna Dam so that the statistical law of progressive failure process in dam body are revealed; Secondly,for the calculation of the failure probability,mathematical model and formula are established according to the characteristics of gravity dam,which include three levels,that is element failure,path failure and system failure.A case study is presented to show the practical application of theoretical method and results of these methods.

Effect of Failure Mode of Taut Mooring System on the Dynamic Response of A Semi-Submersible Platform

Mooring system failure can lead to largely different dynamic response of floating structures when compared to the response under the condition of intact mooring system.For a semi-submersible platform with taut mooring system under extreme environmental conditions,the typical mooring system failure includes anchor line breaking failure due to the broken anchor line,and the anchor dragging failure caused by the anchor failure in the seabed soil due to the shortage of the anchor bearing capacity.However,study on the mooring failure caused by anchor failure is rare.The current work investigates the effect of three failure modes of taut mooring system on dynamic response of a semi-submersible platform,including one line breaking failure,two lines breaking failure,and one line breaking with one line attached anchor dragging failure.The nonlinear polynomial mooring line model in AQWA was used with integrating the load and displacement curve from the anchor pulling study to characterize the anchor dragging behavior for mooring system failure caused by the anchor failure.The offsets of the platform and the tension of mooring lines were analyzed for mooring system failure with 100-year return period.It is found that the mooring failure of one line breaking with one line attached anchor dragging is a case between the other two mooring failures.The traditional mooring analysis considering only the damaged condition with one line breaking is not safe enough.And the simple way of mooring analysis of two lines breaking is too conservative for the costly offshore engineering.

Instrument Automation Control System Faults and Maintenance

This article explores the topic of fault diagnosis and maintenance strategies for instrument automation control systems,analyzing them through specific cases.The aim of this research is to improve the stability and reliability of the system by conducting a thorough investigation of faults and maintenance in instrument automation control systems.By doing so,this research hopes to provide a strong guarantee for the smooth progress of industrial production.

REPAIRABLE SYSTEM AVAILABILITY MODEL WITH RESPECT TO LIFE DISTRIBUTION OF SPARE PARTS

The failed components of repairable systems are replaced with spare parts that may have different failure distributions from those of the components that have failed. The spare parts may be either the same as new, better than new, or worse than new. This is the reality in maintenance engineering. Repair with better spare parts is defined as ＂super repair＂. The failure distributions of the spare parts affect the availability of the components and their systems. A novel model is proposed to describe the availability of repairable systems across their operating time, at the level of their components, on the assumption that the failed components are immediately replaced. The model functions with arbitrary failure distributions of spare parts. It can be used to compute the availability of components and systems not only under perfect and imperfect repair but also under super repair.

On the Effectiveness of the System Validation Based on the Black Box Testing Methodology

With the advancement of technology in recent years, effective fault diagnosis became a necessity to verify the performance and ensure the quality of complex systems. In this paper, an original verification methodology for complex consumer electronic devices is presented. Verification of the system which consists of hardware （integrated circuit） and corresponding software within a flat panel TV set is in the focus. Proposed methodology provides reliable functional failure detection using the concept of black box testing. Further, the approach is fully automated, improving the reliability and speed of failure detection. The methodology effectiveness has been experimentally evaluated and the analysis results have been reported.