The Progressive Collapse Analysis Of Grid Structure

Progressive collapse of structure initiates as a result of local structural damage caused by unexpected event and propagate to failure of adjoining members, and ultimately lead to the disproportionate part of the initial local damage or all of the structure collapsed. In recent years, progressive collapse are studied by various countries, and a wealth of research results have been made in the field of frame structure. The research method about progressive collapse of grid structure is still rare.On the basis of summarizing the domestic and foreign analysis results of progressive collapse, in this paper, alternate load path method is recommended to be the major analysis method for large-span space grid structure, and uses the general finite element software ANSYS/LS-DYNA in analysising the progressive collapse of large-span space grid structure. In alternate load path method there are two important contents, one is how to determine the position of the failure component, and the other is how to simulate dynamic effect caused by failure component.This paper chooses simplified sensitivity analysis method to judge the important component. The simulation method for failure component including static and dynamic simulation. For dynamic simulation method, the large span space grid structure is sensitive to the initial state of component failure, so this paper adopts the equivalent load unloading method considering initial state. The method uses a simple load-time curve, the initial condition of structure before encountering the local damage and dynamic effect caused by failure component are considered in the curve. So the reliability of the results is improved. For static simulation method, this paper uses dynamic load increase factor to simulate dynamic effect, including scope and value of dynamic load increase factor. According to the analysis of space grid structure, the method of calculating the static effect under the reverse force of the failure components as a basis for considering the scope of dynamic load increase factor is feasible.In this paper, the performance of anti-progressive collapse of grid structure is evaluated. The results show that the anti-progressive collapse of the grid structure is of higher capacity, and the progressive collapse can not occur after single component removal, however the collapse will occur after a plurality of components removal. At the end of this paper, according to the resist progressive collapse measures of frame structure, combining with the assessment results of grid structure, some measures to enhance the resisting progressive collapse ability are proposed in this paper.