Research On Reliability Of Structure Members Based On Fuzzy Failure Criterion

The safety of structures is the most important design problem.The reliability theory provides an effective tool for analyzing the reliability of structures.The classical theory in structural reliability analysis has been very in-depth researched,but it only considers the influence of the randomness,ignoring the influence of fuzziness.The measure that only considers the reliability of design,not including the reliability of real structures,has certain limits.In this paper,randomness and fuzziness have been considered in analysis of structural reliability.In classical reliability analysis,structures from safety to failure is between mutations.Actually structures from safety to failure is gradual,so it is more practical and more reasonable to consider fuzziness in reliability analysis.In this paper,based on the fuzzy failure criterion,the fuzzy random reliability analysis of the ultimate bearing capacity limit state of common structural members and the serviceability limit state of recycled concrete flexural members is carried out.The main work of this paper includes:(1)By reviewing the basic theory and calculation method of reliability,the JC method that based on the MATLAB program is used to calculate the reliability index of the ultimate bearing capacity of common structural members.The validity of the program is verified by comparison with the target reliability index from codes,which is considered as the basis of the analysis of the fuzzy failure criterion,and the reliability index of structural members under earthquake is analyzed;(2)Based on the "security-intermediary-failure" three level working mode,analysis method of performance based design,which provides a theoretical reference for performancebased design,is put forward;(3)According to the definition of the fuzzy event probability,the improved JC method is used to analyze the fuzzy random reliability of common structural members.Based on the adjustment of codes,this section analyzes the fuzzy reliability of structural members which are designed according to the current codes,and proposes a new target reliability index,which helps engineers to grasp the actual reliability level under the current scodes.(4)Based on the fuzzy failure criterion,an improved Monte-Carlo method is used to analyze the serviceability limit state reliability of recycled concrete flexural members,and the influence of fuzziness on the reliability index of deflection and reliability index of the maximum crack width is discussed.The effects of load ratio,reinforcement ratio,concrete strength grade,height and reinforcement diameter on the reliability index are discussed.