Study On The Safety Assessment Method Of Existing Low-grade Highway Concrete Bridges

Medium-and small-span concrete Bridges are the most common and abundant bridge forms in China's low-grade highway system.Most medium and small span concrete bridge in the completion of the lack of specialized management,the actual load is often greater than the actual bearing capacity,led to the use of the structure itself continuously damaged and aging,the original structure of the security and stability of the gradual degradation,when the bridge structure safety tends to limit state,will be a direct threat to the low existing highway concrete bridge structure safety.In order to make better use of existing low-grade highway concrete Bridges,it is necessary to evaluate their safety,so as to provide relevant basis for later operation,maintenance,reconstruction and reinforcement.Low current,our country has both the safety of the highway medium and small span concrete bridge assessment method has to be continued in-depth study,the difference in the long-span bridge,this paper in order to improve its safety assessment conclusion rapid,accurate and scientific,for the purpose of further expansion of existing highway concrete Bridges safety comprehensive assessment method of study,the main research content is as follows:(1)Fully study the current status of bridge testing in China,as well as the domestic and foreign research status of safety assessment,to lay a foundation for the following.(2)Basic theoretical research on safety assessment of existing low grade highway concrete Bridges.To summarize the classification of bridge system,bridge structure,existing bridge inspection and evaluation;This paper analyzes the problems existing in the existing bridge safety evaluation standard,and proposes the existing bridge safetyevaluation standard based on the civil building safety evaluation standard(examining the bearing capacity and the bearing state capacity).(3)Study on the safety evaluation index system of existing low grade highway concrete Bridges.According to the safety indexes in previous literatures,the proposed bridge safety standards and concrete bridge structure classification,the initial safety evaluation indexes are extracted.The final indicators were selected through questionnaire survey,and the final indicators were weighted by principal component analysis method,entropy value method and AHP respectively.Finally,Lagrange minimum deviation and combination weighting were used.(4)Research on the safety evaluation model of existing low-grade highway concrete Bridges.By analyzing the evaluation criteria of each index,the safety evaluation model of existing highway concrete Bridges is established by using matter-element extension method.The matter-element,notional domain and classical domain are established.Through dimensionless data processing,correlation functions are established to push up layer by layer,and extension evaluation models of matter-element at the first,second and third levels are constructed.Finally,evaluation grade,correlation degree and feature number are obtained.(5)Example verification.Taking 7 middle and small-span concrete Bridges in a county in Inner Mongolia as an example,the safety evaluation model of existing low-grade highway concrete Bridges established in this paper is applied to evaluate,and finally evaluate their safety grade and correlation degree,so as to verify the operability and rationality of the model.The calculation in this paper is done by combining manual calculation with excel table.