| With the social development, it has become a important constituent of a project to restore and remedy a building, especially to the structures of the electric system. But, on the basis of the detailed suvery of the structures, the workload is extraordinary enormous, even if just to survey and analyze the power-transmission structures of the electric system. This demands to supply a practical method to analyze and evaluate the reliability of the structures of the electric system. Although The Reliability Assessment Standard of Industrial Factory Building (GB J 144-90) and Reliability Assessment Standard of Civil Building(GB 50292-1999) has beem issued by the state, there are not any homologous standard to judge the reliability of power-transmission structures. From the requirement of electric system, the reliability assessment of electric system of Hena province is analyzed by eletementory theories and methods of probabilistic theory , fuzzy mathematics, steel structure and reinforced concrete.First, the development history of the reliability theory is reviewed, the basic methods of reliability assessment are summarized and the defects of the reliability assessment at the present time are analyzed and the problems demanding to be solved are put forward.The reliability of a system is the probability of the system to finish its prearranged function within the schedule time and under the rated condition. It reflects the synthetical requirements to the engineering design, represents the unity of security and economic and can harmonize the contradiction between the near invest and the long-range benefits. The basic theories are summarized from the aspects of the three uncertainties influencing the structure reliability , the limiting state of the structures , structure reliability and inventory survey of the in active service structures.The research of the security assessment of the structures is quite a lot, but the research of the applicability and viability is insufficient. A concept is put forward that the the reliability of power-transmission structures should be divided into two aspects: security assessment and applicability assessment. On this basis a method called fuzzy comprehensive evaluation is renderd to analyze and evaluate the power-transmission structures.The basis of the method of fuzzy comprehensive evaluation is the judgement of the single factors and the important step is to ascertain the subordinate function. Based on the acquirement of the power-transmission structures, the single factors which influence the reliability of power-transmission frame are analyzed and the subordinate functions are established and the weight vectors are ascertained by themethod of AHP. The single factors can be analyzed by the stuff of the members and the different types of the structures. Given the aim of the research is to found a method to evaluate the structures preliminarily, only the factors such as the bearing capacity, connections and compages, distortions, cracks are considered.In the process of fuzzy comprehensive evaluate, it is an pivotal step to ascertain the weight coefficients of the members. It is relied on the expertise to calculate the weight coefficients at present and has strong subjectivity and uncertainty and it is difficult to calculate the weight coefficients of complex structures. Whereas the above problems, a study is made of the meaning of weight coefficients and the different kinds of representative power-transmission structures is analyzed by using the Mente-carlo method and a method is rendered to calculated the weight coefficients and the weight coefficients of each member are gained.There are many members hi large size structures, so the weight coefficients distributed to each member is very small, this leads to a result that the information of the injuried members is dispersed. And because the steps of the traditional fuzzy are so more that much useful information are lost in the evaluate process and lead to a incorrect result. There are no good solutions to this pr... |
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