Research On Durability Assessment Of Reinforced Concrete Main Beam Based On Fuzzy Theory

In recent years, with the increasing investment in the infrastructure constructionand the rapid development of bridge, the importance of bridge is more obvious. Dueto the influence of external environment and traffic load, the damage of existingreinforced concrete bridges continuously appear, which increases the maintenancecosts and restricts the development of bridge construction. At the same time, the hugeinvestment and important effect of bridge attract more attention of peoples for thedurability of bridge. The durability assessment of bridge is becoming the key to thebridge maintenance.The accurate and efficient method for bridge durability assessment can providethe basis and premise to make maintenance plan scientifically, which is in favor ofensuring the bridge security in design life. However, in present bridge durabilityassessment methods, human assistance is needed in the evaluation process. Thisresults more human factor influence. There is widespread doubt about the objectivityof durability assessment results. Aiming the numerous indices and hugeness dataobtained from bridge health monitoring system, the traditional method is unable todeal with, effectively. So, on the basis of the research status at home and abroad, thispaper proposed the durability assessment method of bridge superstructure based onfuzzy theory. It can reduce and decrease the influence of human factors and extend theapplicability of durability assessment method. The primary research is as follows.1. The background and significance of durability evaluation were analyzed andexpounded. The research status of the durability assessment is summarized. Theresearch status of fuzzy analytical hierarchy process, fuzzy clustering algorithm andneural network improved by genetic algorithm was summarized. On the basis of theanalysis of shortage of existing bridge durability assessment methods, the research emphasis in this paper was proposed.2. The factors affecting the durability of reinforced concrete bridge was analyzed,and influence mechanism of every factor was stated. Considering the measurability,completeness, objectivity and independence of durability evaluation index, thedurability evaluation index system was established based on analytic hierarchyprocess.3. The triangle attribute function was selected as the membership function. Thedetailed evaluation criterion and specific forms of membership functions weredetermined. On the basis of analytic hierarchy process, the weight of each index wascalculated. The NanPing international boundary bridge was selected as engineeringproject. On the basis of field test data, the durability assessment of this bridge wasrealized using the fuzzy comprehensive evaluation technology. The present degree ofbridge durability was determined.4. The durability assessment method based on fuzzy clustering algorithm andneural network improved by genetic algorithm was proposed. Firstly, in order toconstruct ideal output vectors, the cluster analysis of training samples for neuralnetwork improved by genetic algorithm was adopted based on fuzzy clusteringalgorithm. Secondly, the initial weights and thresholds in BP neural network wereoptimized based on genetic algorithm. The trained neural network realized theforecast and evaluation of durability degree of testing samples. This approach makesfull use of the characteristics of the data itself, reduces the influence of humanobjective factors and is able to utilize the bridge health monitoring data, whichimproves the effectiveness and objectivity of bridge durability assessment.