Research On Structural Condition Assessment Methods Based On Extension Theory

Structural state assessment is an important part of structural health monitoring. The final purpose of a health monitoring system and a series of preparatory work is to get the level of state of the structure timely and accurately, so as to take effective measures to ensure the safe operation of the structure to guarantee the safety of the people and social property. Therefore, researches on the structural condition assessment method are increasingly concerned. Here the extension theory is applied to structural condition assessment, the main work in this paper are as follows:(1) This paper summarizes the previous methods used in the structural condition assessment, and then introduces the basic concept of extension theory, the problems it will solve and its application areas. Here the extension theory that is used to solve contradiction is applied to structural damage assessment, this gives the structure damage assessment method a new development.(2) In order to get the more reasonable weights of evaluation indexes of extension theory, the Criteria Importance Through Inter-criteria Correlation (CRITIC) method is introduced to calculate the objective weights while the Analytic Hierarchy Process (AHP) method is used to calculate the subjective weights. The integrated weights of indexes of extension assessment theory are established by combining the subjective and objective weights via game theory. Finally, taking four frame structures as example, the comparative analysis of seismic damage assessment is carried out by the proposed method and several other methods. The results indicate that the integrated weights of extension evaluation theory overcome the limitation of single weight, which has more advantages.(3) The cloud model is introduced to extension assessment theory for ignoring the uncertainty of boundary value for evaluation in the extension assessment theory. Considering the characteristics of uncertain reasoning of cloud model and the qualitative and quantitative analysis of extension theory, extension assessment method based on cloud model is built up by improving the Membership function through the cloud transformation and establishing credibility factor by statistical results and other steps. Finally, apply the extension cloud evaluation method for seismic damage assessment of structures. It is proved that the improved extension cloud evaluation theory is an effective comprehensive evaluation method by the comparative analysis with other evaluation methods. (4) Considering the uncertainties due to ambiguity, vagueness, and fuzziness which are statistically non-describable, an extenics fuzzy pattern recognition method is used to perform damage state assessment. In this method, healthy observations are used to construct a fuzzy set which represents health performance characteristics. Besides, the bounds on the similarities among the structural damage states are prescribed. Thus, an optimal group of fuzzy sets representing damage states can be inferred as an inverse problem from health observations only. Piecewise linear functions are used as fuzzy membership functions representing the states of healthy and damaged. The optimal group of damage fuzzy sets is used to recognize unknown state of damage via maximum correlation degree. At the end, a case study for damage pattern recognition of a model steel bridge is presented and discussed. The approach is capable of identifying damage patterns accurately.