Analysis On The Fuzziness And Reliability Of The Crack Width Limit Of Concrete Flexural Members

Crack width control is an important content to ensure the applicability of concrete flexural members,the design standard requires that the maximum crack width of members should not affect the normal use of members.The current research results and engineering practice show that the failure criterion itself has great fuzziness,so it needs to use the membership function in fuzzy mathematics to describe,and this uncertainty has an important influence on the reliability of crack width control.However,there are many deficiencies in the research on the fuzziness and its influence of failure criteria at present:First,In the reliability analysis of structures,the research at this stage does not pay enough attention to the fuzzy factors;Second,In the current fuzzy reliability analysis,there is a strong subjectivity in the selection of membership functions and the determination of parameters;Third,In the reliability analysis of structures,random variable combination is generally used,and the conclusions are mostly obtained by enumeration method,which lacks certain universality;among them,membership function generation method and reliability analysis model are the key research contents of this paper,and they have a great influence on the reliability analysis results of crack width control of components.Based on the above shortcomings,this paper first proposes the indirect statistical method based on the boundary,then obtains the membership function and reliability analysis model under different conditions according to the statistical data,and finally reveals the reliability level of crack width control of concrete flexural members.The main research work includes:1.In the fuzzy statistical method of generating membership function,the concept of fuzzy boundary and indirect statistical method of membership function are explained in this paper,so as to reflect the real intention of the respondents with more accurate local method;2.In the reliability analysis of crack control of concrete structure,through group investigation,indirect statistical method is used to obtain Under different conditions,the membership function of failure criteria reveals the fuzziness of failure criteria more accurately and objectively;3.Based on the current research results,the reliability analysis model of dimensionless and random process combination of component crack width control is established,and the influence of fuzziness of failure criteria is taken into account;4.Based on the above research results,the fuzziness of reinforced concrete components and prestressing are respectively considered.The reliability level of crack width control of concrete flexural members is analyzed and revealed comprehensively,and the main influencing factors(such as reinforcement ratio and relative ratio of action)are defined.The research results of this paper not only improve the generation method of failure criterion membership function and the reliability analysis model of crack width control in theory,but also reveal the reliability level and main influencing factors of crack width control of concrete flexural members more comprehensively and accurately in engineering application,which can provide reference for improving the control method of crack width of concrete flexural members.