Numerical Investigation of Instability of Complex Spatial Structures

Consistent Imperfection Mode Method (CIMM) is a widely-used and effective numerical method to study the buckling capacity of spatial structure. CIMM used an “artificial” deformation instead of “artificial” load eccentricity to imitate the initial disturbance/imperfection for calculation of buckling load, and the basic mode obtained from linear buckling analysis could be used to simulate the distribution of imperfection. But in linear buckling analysis of certain complex spatial structures, the basic and first few modes usually reflect the local buckling of certain slim elements, and stability of complex structure depends on none of these local modes. Based on mode energy discrimination criterion, the improved CIMM is introduced. Improved CIMM includes following steps. 1) Normalization of all buckling modes. 2) Summarization of each mode of strain energy. 3) Discrimination of global modes with peak strain energy. 4) Based on first few global modes, CIMM could be used to calculate buckling loads respectively. 5) Choose the smallest buckling load as the buckling capacity of structure.