Parametric Study On The Progressive Collapse Design Method Of Frame Structures

With the increasing of terrorist attacks worldwide, more and more researchers start to focus on the problem of the progressive collapse of building structures. Local damage of buildings may be caused by the accident loads, such as the earthquake, explosion, fire disaster and so on. The progressive collapse of structures is defined as the spread of an initial local failure from element to element, eventually resulting in the loss of bearing capacity for main structure and the collapse of a disproportionately large part of it. The consequences would be catastrophic once the happening of progressive collapse of building structures. As a result, all kinds of extreme loads must be taken fully into consideration in order to improve the progressive collapse resistance of building structures and to ensure the safety of life and property for people.Firstly, based on the GSA2003and DoD2009standard, the advantages and disadvantages of linear static analysis, linear dynamic analysis, nonlinear static analysis and nonlinear dynamic analysis methods were analyzed by using SAP2000structure analysis software. Results show that the steel dosage of structure designed by linear static analysis is30percent more than that designed by nonlinear dynamic analysis, which indicate that the structure designed by linear static analysis is much more conservative. The dynamic increase factor (DIF) value of2.0given by GSA may be suitable for linear static analysis, but overestimated for nonlinear static analysis.Secondly, the influence factors of nonlinear dynamic analysis during progressive collapse of RC frame structures were studied. The influencing factors of the member failure time, structural damping and the member failure location were studied illustrated by the case of two-dimensional models with different height and bays. The result would provide basis for selecting reasonable parameters for the design of progressive collapse. Results demonstrate that the dynamic effect increased with decreasing the member failure time but decreased with increasing structural damping. The dynamic effect of RC structures after removing the corner column is greater than that after removing the interior column.Finally, in order to research the value of DIF of nonlinear static analysis during the progressive collapse design of RC frame structures, the influencing factors of maximum plastic angle, height, width, reinforcement ratio and the lengths of bay were studied systematically. The results demonstrate that the DIF of different models has the same trend and the maximum is about1.13, which is far less than that given by the GSA Standard. The DIF decreased with the increasing plastic angle but increased with the increasing reinforcement ratio. Other factors, such as the aspect ratio, the lengths of bay, the section sizes and the loading pattern, had no significant influence on the DIF.