Reliability Analysis Of Structural Systems Consider Static Strength, Fatigue And Stability Simultaneously

Several kinds of failure modes take place when various loads act on the structural system, mainly including static strength failure, fatigue failure, and the stability failure of the vimineous bar or the vimineous structure under pressure etc., and each failure mode has a large influence on the system safety. However, within the present analysis of structural reliability, the reliability research of stability failure is less. But that can bring the serious aftermath, especially, the concealment of the whole structure system's stability failure is strong. Once it happens, tremendous destruction will be caused. Moreover, the present reliability analysis of the structural system under static load or fatigue load is mostly considered respectively. But the mixed case of several failure modes is very likely to occur for the structure system. For example, certain fatigue damage, caused by the lesser fatigue load, makes the ultimate carrying capacity of the structure decreasing. And the structure may even destroy completely because of the ultimate load. When analyzing the structural reliability, the influence of different failure modes on the cumulative damage of the hinder elements should be considered due to the effect of fatigue load. And besides the relativity among those failure modes, it makes the failure mechanism of the structure more complicated and the reliability analysis of the structure system more difficult. For the above problems, the research has been done in this thesis, such as follows:1) In order to calculate the reliability index of the non-linear safety margin accurately, a new method-the Joint Method is introduced based on the Design Point Method and the Mean Point Method, which not only simplifies calculation but also improves accuracy of the calculation.2) Based on the crack propagation, the failure mechanism of structure system under static load and fatigue load is analyzed concretely. And considering the static strength and the fatigue synthetically, the method of reliability analysis under the two kinds of loads is given. 3) The methods of reliability analysis for the moving vimineous bar and structure system stability are given. First, aiming at the problem of stability for the elastic vimineous bar, the mechanical models are established. Based on the differential equation of the bar with small defection, the buckling critical load of vimineous bar is confirmed. And then the reliability analysis of the structure is carried out. The reliability index and failure probability are calculated. The critical load and the reliability index of the bar are analyzed under the influence of initial eccentricity. Secondly, the stability characteristic equation of the structure system is deduced. The critical load of the whole structure system's stability failure is calculated. Thereby, the safety margin of that is established, and the stability reliability of the structure system is analyzed.4) Considering the failure modes of static load, fatigue and stability failure simultaneously, the method of reliability analysis of the structure system is given. For a structure system under static load and fatigue load, because of the influence of fatigue damage, the mechanical characteristics of resistance and elastic module of the element will decrease along with the increase of time. The whole structural reliability will decrease along with the failure of element and the attenuation of module. Thus, combine with the cumulative damage theory, the time of failure for different failure modes is given. Furthermore, considering the remnant structure's stability failure in the failure route, the reliability analysis of the structure system is done by the theory of system reliability.