Simplified Nonlinear Dynamic Analysis by Hexagonal Collapse Surface Model of Steel Frame Structure

Based on the need for effective evaluation of multistorey structures response to seismic loading, this research includes the study of simplified nonlinear dynamic analysis (SNDA) by hexagonal collapse surface model. Existing conventional analysis methods such as FEMA440, restrict the extended use of Nonlinear Static Procedure (NSP) and Nonlinear Dynamic Procedure (NDP) by using the equivalent one‐degree‐of‐freedom (SDOF) model on multi‐degree‐of‐freedom (MDOF) structure. A large error known as Multiple‐Degree‐of Freedom Effects occurs in the elastoplastic behavior. To overcome the limitations of this analysis technique, the understanding of it in the entire structural system due to the influence of the higher‐order vibration modes are investigated, in addition to distinguish the elastoplastic behavior of a structure more precisely. Based on the important collapse mechanisms that are probable to occur during earthquake response, the development of a simplified dynamic analysis technique in which higher‐order vibration mode components were extracted to construct the plastic collapse safety region of a structure. Simplified nonlinear dynamic analysis (SNDA) aims to develop such method whereby multiple vibration mode components are properly considered. Primary and secondary mode of vibrations are generally examined with multiple load patterns corresponding to the condition whereby several independent variables reach maximum concurrently. The formation of hexagonal plastic collapse surface from the probability limit analysis based on proportional load results was discussed. The target for this study is to investigate the competency of this simplified analysis approach in seismic response of structure evaluating techniques.