Robustness Research On Structures Of Bar System

Structural robustness means the capability of resisting disproportionate collapse when the structure suffering unexpected loads.It is an important indicator to the integrate safety of structure.How to evaluate the structural robustness quantitatively is an important problem in structural reliability research.To insure the topological importance single component in structure of bar system and analyze the influence on the reliability of the structure after they were failed,it is necessary to propose a new method to calculate the importance coefficient of component and evaluate the structural robustness quantitatively.In this present thesis,we will do some groping research on the related problems of the bar structure.Firstly,to express clearly the geometrical/topological configuration of components in structure,the redundancy matrix is established by means of principle of minimum potential energy.The values of the elements in the matrix indicates the importance of the corresponding members in geometric / topological relations of structure.The redundancy of the structure is resoved into redundant components.With the redundancy matrix,a robustness index is given,and the concept of internal force matrix is developed.Secondly,based on principle of minimum incremental load,the method of establishing the failure space in the system reliability analysis is discussed.Then a new method of solving the system reliability by finding failure space is proposed through this way.The core of this method is to avoid calculating the common probability space of each failure mode,only the first failure mode is reserved in homologous branch during the main failure mode screening process,as a result the total failure probability of the system is a form of direct sum.Thirdly,the importance coefficient of the components is evaluated on the basis of obtaining the system failure probability,and a new indicator of structural robustness and a method to evaluate it is given with this importance coefficient of the components.The method and conclusion in each chapter is illustrated in examples which compared with former method.The accuracy and feasibility of these method is proved,which can provide the reference for evaluating the integrate safety of the structure.