| Structural system reliability theory was the difficulty of the research field of structural reliability.However,there are several key problems unsolved which restricts the development of structural reliability design theory from the component reliability level to the system reliability.There are two main problems in structural system reliability analysis:one is how to identify the dominate failure modes efficiently and accurately,and the other one is how to calculate the joint failure probability of failure modes.Due to the randomness of material parameters,loading condition,and geometry size,there would be a large number of potential failure elements and failure modes.The traditional failure mode analysis method usually cannot balance the accuracy and efficiency,since it is lack of efficient branch and bound strategy:on the one hand,to ensure the efficiency,it often misses the dominate failure elements and failure modes;on the other hand,to ensure the accuracy,it often induces combinatorial explosion since too many potential failure elements are selected.Hence,there still lacks an efficient system reliability analysis method which can achieve the adaptive bounding and unzipping.This thesis focuses on the efficient adaptive method for system reliability analysis,which induces following main contents:(1)Taking into account the difference between the total virtual load effect and the common external load effect,the incorporated sectional strength capacity technology was proposed for the total virtual load effect and the section strength.Then the modified structural calculation model was established and the? unzipping method was proposed based on the incorporated sectional strength capacity technology.The proposed method is of high accuracy,since it corrects the mistake of traditional method by superimposing the total virtual load effect and the common external load effect simply.(2)The dynamic bounding threshold and criterion were determined based on the definition of the uniformity of failure probability(UFP),the reference failure probability(RFP)and the reference reliability index(RRI).Then,an improved ? unzipping method for structural system reliability analysis was developed based on the adaptive dynamic bounding threshold.The improved ?unzipping method is of high accuracy and efficiency,since it takes into account the distribution of failure probability for identification of potential failure elements in every stage of failure evolution.Meanwhile,the improved ?unzipping method can avoid missing the doninate failure elements and failure paths,and overcome the shortcomings of traditional methods.(3)According to the principle of equivalent normalization and orthogonal transformation,the non-normal random variables can be transformed into independent normal random variables.Then an improved ? unzipping method for structural system reliability analysis with non-normal correlated variables was developed.The improved ? unzipping method can not only take into account the influence of distribution type of random variables on the bounding threshold and failure evolution,but also be used to analyze the influence of the distribution type,correlation and variability of external load and full section plastic resistance on the dominate failure path and system reliability index.(4)The accuracy and applicability of there improved ? unzipping methods were validated based on the multi-story and multi-span frame structures,by comparing with the Monte Carlo method.Meanwhile,the influence of distribution type,variability and correlation of external load and full section plastic resistance on failure evolution,dominate failure path and system reliability index were analyzed.The analysis results show that the system failure probability increseswith the increase of correlation and variability of external load and full section plastic resistance,especially the full section plastic resistance has a significant influence.Furthermore,the system failure probability increses with the increase of leteral load. |
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