Importance Coefficients Of Components In Quantitative Evaluation Of Structural Robustness

Consideration of structural robustness is one of the most important measures to guarantee the structural safety, especially to deal with unexpected events. How to evaluate the structural robustness quantitatively is one of the most challenging advanced problems in structural engineering. In the present thesis, a new method on importance coefficient calculation of components in structural robustness evaluation is given, which is focusing on the change of structure capacity after removing some component in the structure. The main contributions are described in the following aspects:(1) The index of component importance coefficient is put forward. And the structural topological relation, the component stiffness and strength, and the effect of external loads are all considered synthetically. The loading process is ended until the structure becomes a mechanism, to some extent, which helps to show how the failed component influences the remnant ones microcosmically and establish the relationship between component importance and structural robustness macroscopically. At the same time, a method called perturbation is used. It bridges the structural stiffness matrix before removing some component with that after removing, by which the rearrangement and inversion of the structural stiffness matrix can be avoided.(2) Two preliminary improvement measures, so called ductile component-exchange method and sub structure-exchange method are given. On the basis of previous qualitative studies, research in this paper specially considers the working mechanism, influence degree and availability status of these two measures from the standpoint of quantitative analysis. In the procedures, the conceptions of member influence coefficient and equivalent stiffness degeneration are introduced to explain the different effects of ductile and fragile materials on the member internal force redistribution and the performance change of the sub structure and then of the whole system with some components failed in it.(3) As practical examples, some plane trusses of full-stressed design are applied with their importance coefficients of components calculated and compared with the indexes in imformed researches. Also, the preliminary improvement measures are given to show the correctness and rationality of theoretical analysis.