Progressive Collapse Design And Ductile Analysis For Frame Structures

Since the collapse of the Ronan Point Tower in United Kingdom in 1968, the structural engineering profession has become more concerned with the phenomena of progressive collapse. Europe and America have done much research on this issue for nearly 40 years and developed relevant design codes or guidelines. However, codes in China have not proposed in detail on progressive collapse. Consequently, based on the design procedure prescribed in GSA, the behavior of a typical Chinese 6-story reinforced concrete frame is analyzed. The main contents of this paper are as follows:1. A 6-story reinforced concrete frame building designed according to the current design code (GB50010-2002) is analyzed using the structural finite element analysis software SAP2000. Four methods for progressive collapse analysis are compared by employing increasingly complex analytical procedures: linear-elastic static, nonlinear static, linear-elastic dynamic and nonlinear dynamic methodologies. Each method is thoroughly investigated and common shortcomings are identified, along with advantages and disadvantages, using side-by-side comparison.2. The internal forces of the critical elements before and after the removal of the column are compared by using the linear-elastic static method. Three different locations for removing column are considered: internal, corner and middle column. In addition, the influence of story located for removal columns on the internal forces in residual structure is discussed.3. The formula for calculating the plastic rotation is derived based on the stress-strain relation of steel and concrete prescribed in the current concrete design code (GB50010-2002). The derived formula is also applicable to the case that the reinforcement ration is closed to balanced failure condition compared with an existing one. A simplified formula is further presented by optimizing the main parameters influencing the plastic rotation. The simplified formula is simple enough to manual calculation.4. The required plastic rotation to obtain the redistribution of internal force for the initial damaged structure and the capacity of plastic rotation of element is analyzed for a 6-story reinforced concrete frame building designed with the current design code (GB50010-2002) under the constant ratio of tensile reinforcement and various ratio of compressive reinforcement. The critical ratio of compressive reinforcement is obtained by comparing the two plastic rotations.