Comparison On Progressive Collapse Design Methods Of Reinforced Concrete Frame Structures And Performance Verification

Since the progressive collapse of the Ronan Point apartment building in United Kingdom in 1968, the collapse of building structures due to the accident has become a serious threat to public safety. Foreign scholars have been doing much more intensive researches on this issue for over 40 years than domestic scholars. In order to do the progressive collapse design of building structures, the developed countries published the relevant codes one after another. Some of them are most representative, such as"Progressive Collapse Analysis and Design Guidelines for New Federal Office Buildings and Major Modernization Projects"(hereinafter GSA2003) and"Design of Buildings to Resist Progressive Collapse"(hereinafter DoD2005) in the United States. It is remarkable that the Department of Defense of U.S developed the revised criteria of"Design of Buildings to Resist Progressive Collapse"(hereinafter DoD2009) last year. However, codes in China have not yet proposed in detail on the resistance of progressive collapse. Therefore, it is prominently valuable for us to do the comparative analysis of the codes in U.S. It is also important for scholars and engineers in China to study the progressive collapse-resistant behavior of the reinforced concrete frame structures and the practical design methods to increase its capacity to resist progressive collapse.The main content herein is as follows:â‘ Introducing the definition of"progressive collapse"of the building structures and the significance of this study in brief, and then reviewing the research findings home and abroad preliminary.â‘¡Doing the comparative analysis about the codes of GSA2003, DoD2005 and DoD2009 seriously, and finding the difference among them in the areas of application, load combination, analysis method, parameter difinition, damage limits and failure criterias. Then, summarizing the development trend of the codes for progressive collapse design of the building structures.â‘¢Based on the finite element model of a 11-storey reinforced concrete frame structure, this paper will represent the analysis procedures of static linear, static nonlinear and dynamic nonlinear methods for progressive collapse study in the software SAP2000. Then, further comparative analysis among the three codes will be done and some reasonable suggestion about the value of Dynamic Increase Factor in GSA2003 will be proposed.â‘£Referring to the Alternate Path (AP) Method in DoD2009, the capacity to resist the progressive collapse of a typical Chinese 6-story reinforced concrete frame was analyzed. And then the frame was re-designed with the AP Method, using the static linear, static nonlinear, dynamic nonlinear procedures respectively.Based on the above research, the main conclusions are as follows:â‘ The analysis and design methods in DoD2009 are much more effective than that in DoD2005, because the Performance-based Progressive Collapse Design Methods and the reasonable Dynamic Increase Factor and Loading Increase Factor are adopted. It's conservative for GSA2003 to define 2.0 as the Dynamic Increase Factor in the static nonlinear procedure. The equation of Dynamic Increase Factor in DoD2009 is recommended to GSA2003.â‘¡Based on DoD2009, the typical Chinese 6-story reinforced concrete frame structure model whose seismic fortification intensity is 8 degrees(0.20g) has good progressive collapse-resistance behavior, when the column at the bottom floors is removed instantaneously. The higher the position of the removed column, the weaker the ability to resist progressive collapse. When the column on the top floors is removed immediately, the remaining structure will collapse.â‘¢Based on DoD2009, it is non-conservative to analyze the progressive collapse-resistant behavior of frame structures by the static nonlinear method comparing with the dynamic nonlinear one.â‘£When the model is re-designed by the static linear method, the total amount of beam reinforcement will incease 5% approximately. When re-designed by the static nonlinear method, it will increase 3%. When re-designed by the dynamic nonlinear method, it will only increase 2%. Although the results of nonlinear method is more accurate than linear one, it's more complex and time-consuming. Therefore, the static linear method for progressive collapse design of frame structrures is recommended in practice.