| 1. IntroductionThe aging and damage of buildings in the natural environment is an inevitable, irreversible process. Structural full longevity processes basically could be divided into three main phase: construction phase, operational phase and aging phase. Upon the investigations, the mean failure rate of the structure is higher during construction phase and aging phase. Whereas, in the field of structure reliability, less studies are focused on the aging phase currently. So we need not only keep on increasing the design level of structural reliability, the more realistic, and exigent task are the studies of the reliability evaluation theory and maintenance decision means for the structures on active duty.On the basis of survey of transformer substations' structures in a certain electric network, the phenomena of aging and deteriorating occurred in respectable power transformations structures, such as the carbonization and tarnish on the surface of structures, the sag of protecting coatings of concrete components, the rusting of the steels etc. Such phenomena directly threaten the regular services of the structures. In the modern society, electricity, as a sort of energy source, has become the requisite materials basis of national economy. Once the transformer substations' basic constructions-power transformation structures brake down or collapse, the aftermath will be very serious.However, because of the various styles and bulky quantity, it is unpractical to reinforce and restore all the structures, and it is irrational in the point of economical views. Therefor, we should reinforce and restore the structures according to structures' quality actuality to decrease the unnecessary outlay and spending. So, it is necessary to study the method of reliability assessment and analysis for the power transformation structures based on damage, by which we can assess the power transformation structures' reliability through scientific means.During a long time, some methods such as traditional experience method, syntactical identification method, utility identification method were used in reliability evaluation for the structures on active duty. And now, we use the reliability assessment standard to grade the buildings, and based on it, collapse mechanism method, fuzziness ensemble judge method come into use. Though the method of grading is easy of handing, but the trend of the reliability assessment standard's development is calculating the numerical value of the structures' reliability, and residual life method, fuzzy reliability method and Monte Carlo method are just about the powerful instrument for getting the reliability values. Furthermore, with the appearance and perfection of some new theories, some new means, such as expert system method, genetic algorithm, neural network method, gradually develop and enter the utility phase.Considering the purpose of study and referring home and broad research production, this article plans to adopt Monte Carlo-finite elements method to proceeding power transformation structures' reliability analysis based on damage.2. the rationale of reliability analysis considering damageThe rationales involved in the methods adoptive in this article mostly include: reliability theory, finite element theory, Monte Carlo theory and sensitivity theory etc.The reliability assessment for the structures on active duty developed base on the notions and practical methods of structure reliability design, and at present, the methods which are used more are probabilistic limit design means based on reliability theory. This method first gives a clear definition of structural limiting state: if the whole structure or part of the structure exceeds a certain state, the structure will not satisfy the a certain functional requirement stated in the designs, then the state is called the limiting state. The equation of the structural limiting state can be expressed: Z=R-S, thereinto R and S respectively are structural resistance and load response expressed with stochastic variables, we ca... |
PDF Full Text Request