Study On The Progressive Collapse Dynamic Effects Of The Irregular Frame Structures

Progressive collapse of the structure is a complicated dynamic process, how to consider the dynamic effects reasonablly is the key to study progressive collapse. Scholars both at home and abroad mainly focus on the dynamic effects of the regular structures, but the systematic study on irregular structures is scarce. A vertically irregular structure is selected as the analysis object and a coal preparation plant is selected as the the engineering project to study the progressive collapse dynamic effect of the irregular frame structures.Based on the basic principle of objective weighting method, a comprehensive assessment of the element importance is proposed, by which three independent evaluation indexs of average stress ratio, rigidity degradation factor and stable degradation factor are to be optimized for making the assessment of the key components of the structure more reasonable and accurate. In the application of objective weighting method to assess the importance of the members is verified through one framework. The results show that the objective weighting method can be well applied to evaluate the the key elements of structure, and show a better superiority than the individual evaluation.By adopting the beam element with plastic hinges and rigid zones at member ends, an analysis model of the vertically irregular plane frame structure is established. The relations of the progressive collapse dynamic effict of vertically irregular plane frame structure with the location of failure members, storey and demand capacity ratio are discussed by use of the instantaneous applied load method. The results show that the progressive collapse dynamic effict of the position of structural stiffness mutation occurrs initial damage is the largest; when the structure at the plastic state, the dynamic amplification factor of the structure change greatly with demand capacity ratio.Considered the space work for the frame, the relation of the progressive collapse dynamic effict of a vertically irregular space frame structure with spatial location is discussed. The dynamic amplification region of such generally irregular frame structure is defined and the value of dynamic magnification factor is offered. The results show that the role of spatial structure can significantly reduce the dynamic amplification effect of progressive collapse.A simplified analysis model of the main workshop of a coal preparation plant reinforced concrete frame structure is established. By use of basic methods, the progressive collapse analysis of the coal preparation plant reinforced concrete frame structure is conducted to study the progressive collapse dynamic effect of the complicated irregular framework. The results show that, the spatial distribution of the progressive collapse dynamic effect of the complicated irregular framework shows anomalous, so the static analysis methods can not be used to the progressive collapse analysis of the structures.A new assessment of the element importance is proposed, and the progressive collapse dynamic effect of irregular frame structure is presented. The results show that the proposed method can assess the key elements more comprehensive, and the progressive collapse dynamic effect of generally irregular and complicated framework are significantly different. The results has important theoretical significance and engineering application in the structural resistance of progressive collapse.