Time-dependent Reliability And A New Approach To Efficient Solution For Structure System Reliability

Reliability analysis of structural systems is the basis and premise of conducting structure design,carrying out practical engineering structure safety assessment and optimization of maintanance meansures.Reliability analysis of existing structures includes two parts:component reliability analysis and system reliability analysis.And how to obtain the reliability of structural system from the reliability of components is the key point in the structural system reliability analysis.The study in this paper was made around the above point,and the main results are as follows.Based on the probability evaluation system,an algorithm named bounding method for finding the main failure modes of structure is proposed.The method effectively deletes the failure modes that have little effect on the failure probability of structural system and improves the efficiency of the main pattern recognition in structural system.A new method for fast and efficient solution of structural system reliability is put forward.Firstly,the safety margin functions of structural element and the corresponding failure probability are determined by application of structure analysis principle,the element with maximal value of failure probability is then removed and substituted by virtual force to form a new structure,and then reanalysis for the new structure is carried out.By following the steps above,until the mechanism is formed,the structure system reliability is finally determined to be the failure probability of the component in the last step.Case studies comparing with those existing methods show that the proposed method is simple,less calculating workload,high efficient calculation accuracy as well as failure path available,which is suitable for the system reliability calculation of large scale structure.According to the assumption of resistance independent incremental process,a complete analysis model of resistance stochastic process is established,by which the resistance varying with time is taken into consideration.The service life of the component is divided into several equal time periods,and then the time-dependent reliability of the component is obtained based on series structral reliability theory.Case study indicates that the proposed method is simple as well as in conformity with the Monte Carlo method.It can be used as a basis method for reliability of existing structural components.The reliability of structural system is obtained from the reliability of components by adopting the three-level decomposition of syste-subsystem-component.Case study comparing with Monte Carlo methods shows that the proposed method is high efficient calculation as well as the failure probability of the structural system varies with time available,which provides the theoretical basis for the state evaluation,life prediction and maintenance strategy of the existing structural system,and has great economic and social effects.