Study On Bridge System Reliability Based On Random Process And Fuzzy Comprehensive Evaluation

Bridge Health Monitoring System can be divided into five parts which contain onlinetesting, timely analysis, damage diagnosis, condition assessment and maintenance strategydecision. The bridge system reliability analysis is a key part in condition assessment.Because the bridge components reliability analysis is more mature now, even quite anumber of research results have been applied. The entire bridge system reliability mostlyrefer to component reliability research methods then look for the failure function of thebridge system. Since bridge system is very complex, the determination of the failurefunctions often is very difficult. Based on the above situation, this article will look forindexs and methods of bridge structural system reliability assesment on the basis of theexisting mature component reliability, study to make most use of the component reliabilityanalysis research, and to make the bridge system reliability closely linked with thecomponent reliability index, to find the relationship between them.Based on random process related theory this article proposed the Markov processsteady-state probability as assessment index of bridge structural system reliability at thesame time proposed the confirming method of bridge system reliability relational matrixR. Establish the relationship between Markov process steady-state probabilities and thebridge components reliability index. Bridge components reliability is reduced, the damageoccurs. Whether it will be timely and effectively maintained, has a larger impact on thebridge system reliability. Through the transformation of reliability relational matrix R ofthe bridge system established the relationship between the bridge maintenance frequencyand Markov process steady-state probabilities. The failure of the respective members ofthe bridge system in the work process is often not occur simultaneously namely cannotappear the phenomenon of simultaneous failure. Some components are often fail firstly, sothat the remaining members continue to bear all the external load, and generatingre-distribution of internal stress in the bridge system to cause the changes of the othercomponent reliability. In this paper, the assessment methods ofBridge System Mean Tim e T o Failure BSMTTF in the bridge system have beenstudied Bridge system reliability assessment indicators, namely the Markov processstationary probability can be obtained through the analysis of the structural condition of the bridge. However, the value of the Markov process stationary probability is in what intervalrange we can consider that it is reliable and in what interval range it is unreliable.Transition interval must exist also between reliable and unreliable, and the transitioninterval must be vague, so this paper studies a fuzzy comprehensive evaluation methodabout the working condition of the bridge system, and for the first time the steady-stateprobability process is applied to fuzzy comprehensive evaluation of bridge system reducedthe subjective and experiential of fuzzy comprehensive evaluation. In this paper, the maincontent of the chapters are as follows.Chapter1is a review and summary of existing reliability analysis methods. Focuson the summary of the system reliability theory and its application in bridge engineering,and the dissertation of reliability analysis method and structural system reliability analysis.Chapter2study the random process related theory, mainly including the Markovprocess and its characteristics, equation of state of the Markov process and the Markovprocess steady-state probabilities. On the basis of division of the working condition in thebridge system, it put forward a way which using the Markov process steady-state probabilityas a bridge system reliability evaluation indicators additionally study the state transitionmatrix of Markov process steady-state probability calculation equation put forward themethod of determining the bridge system reliability relational matrix and derive therelationship between the reliability index of the bridge components with thesteady-state probability of the bridge system. With the applicability and effectiveness of theexample and the estimation methods of the reliability, verifyed the validity of the method.Chapter3consider the effects on the bridge structure system reliability thatmaintenance rate generate. Through the transformation of the corresponding parameter inthe bridge system reliability relational matrix(R), establish the relationship betweenmaintenance rate and steady-state probability of the bridge system, namely analyze thebridge system reliability and maintainability, obtain the bridge system reliability indicesunder different maintenance rate conditions, draw the relationship between maintenancerate and matrix(R) steady-state probability of the bridge system in a typical bridgestructure.Chapter4consider the transfer of load and stress re-distribution after appearingfirst fail component in the bridge structure system. Through the Laplace transform aboutthe process of steady-state probability calculation equation and reliability function, solving the system state equation after conversion, Bridge System Mean Tim e T o FailureBSMTTF can be obtained then act it as the evaluation of bridge system reliabilityunder the condition of load sharing. At the same time, the method have been given thatusing the Bridge System Mean Tim e T o Failure BSMTTF to analyze the time-varyingreliability of bridge system.In Chapter5, for the specific circumstances of the current state of the bridge systemevaluation, on the basis of using Markov process of steady-state probability as theevaluation of bridge system reliability index, divide bridge system parts and componentsaccording to standards and engineering practice, then select the set of fuzzy evaluation ofthe bridge structure, show the working state space of typical bridges and research fuzzycomprehensive evaluation of the state of the bridge system, for the first time the processsteady-state probability is applied to fuzzy comprehensive evaluation of the bridge system.The evaluation system does not adopt the human scoring method during bridge technicalcondition evaluation process to avoid generating uncertainty and randomness during thescoring process.In Chapter6, sequential failure probability have been simulated through full-bridgemodel, the Markov process steady-state probability of bridge structure have beencalculated, Bridge System Mean Tim e T o Failure BSMTTF have been analyzed, andcarry on fuzzy comprehensive evaluation to the part of the bridge and bridge system byusing fuzzy comprehensive evaluation method. The results show that, the effect that theabove methods are applied in full-bridge model is feasible and effective.Chapter7summarizees the main findings, the main innovations of this paper andreach the following conclusions:1Propose a method of using steady-state probability as the evaluation index ofbridge system reliability. Through the analysis of the Markov process and itscharacteristics, the Markov process equation of state and the process of steady-stateprobability combining with the theory of bridge reliability analysis, put forward theevaluation of the bridge system reliability indicators by using the Markov process ofsteady-state probability and examine the correctness and validity of this evaluation throughboundary estimation method.2Put forward a method of determining bridge system reliability relational matrixand establish the relationship between the reliability indicators of bridge component and the Markov process of steady-state probability. Combining reliability index of the bridgemembers, modify the transfer matrix of the bridge system working state, establish therelationship between the reliability indicators of bridge component and the Markovprocess of steady-state probability.3Establish the relationship between maintenance rate and the Markov processsteady-state probability.Through the tranformation of the reliability relational matrix ofthe bridge system R, consider the effect to Markov process of steady-state probabilitywhich caused by the bridge system maintenance rate, this method can be used to select thefrequency of inspection and maintenance about a bridge.4Deduce the calculation method of Bridge System Mean Tim e T o FailureBSMTTF and put forward the indicators and methods of achieving reliability analysisof the bridge system.Because of the component failure in the bridge structure,there-distribution of the internal stress will occur, through the Laplace transform about thestate equation of the bridge system, deduce the calculation about calculatingBridge System Mean Tim e T o Failure BSMTTF and apply on the exmaples.5Firstly apply this index on fuzzy comprehensive evaluation of the bridge system,reduce the subjectivity and the experience of human scoring process in the fuzzycomprehensive evaluation method. Since the results of bridge system reliabilityassessmentis a probability value, what bridge probabilities are satisfied when the bridgesystem is reliable and what bridge probabilities are satisfied when the bridge system isunreliable, meet what the probability of the bridge system is difficult to judge. Accordingto this problem, combine the fuzzy comprehensive evaluation method, on the basis ofusing Markov process of steady-state probability as bridge system reliability evaluation.In this paper, the bridge system reliability has been analyzed deeply by using themethod of random process. Put forward the evaluation of bridge system reliabilityanalysis, Put forward a method of determining bridge system reliability relational matrixand establish the relationship between the reliability indicators of bridge component andthe Markov process of steady-state probability, derive the calculation method of theBridge System Mean Tim e T o Failure BSMTTF. Combining with Markov process ofsteady-state probability, the fuzzy comprehensive evaluation of bridge components andbridge system have been conducted, Markov process steady-state probability is firstlyused on fuzzy comprehensive evaluation of bridge system. The theory and methods that have been mentioned provide theoretical basis and method for the evaluation of bridgesystem reliability and have important theoretical value in the engineering applications.This research has been supported by grants from Specialized Research Fund for theDoctoral Program of Higher Education (project name: Time-varying reliability analysis ofexisting concrete bridge structures under a variety of failure modes project number:20100061110051) during the process of research and writing, thanks very much.