An Energetic Criterion for Dynamic Instability of Structures Under Arbitrary Excitations

An energetic criterion for identifying the global dynamic instability of structures subjected to any kind of excitations is proposed in the paper. The concept of dynamic stability for structures is firstly interpreted and distinguished from the stability concept in the Lyapunov sense. It is demonstrated that the dynamic instability depends not only on the properties of the structure, but also relates to the change of external excitations on the structure, which distinguishes the essence of dynamic instability from the pseudo static stiffness criterion. This background leads to a novel energetic criterion with which the first passage of the variation of intrinsic energy over the input energy manifests the dynamic instability of structures. The proposed criterion has been extensively tested and verified in the numerical examples, with its advantages clearly illustrated.