Dynamic Stability of Damage-Prone Inelastic Structural Systems

The behavior of a simple mechanical system, experiencing large deformations and inelastic material response with damage. is presented. Because the differential equations that describe the motion are highly nonlinear and coupled for the multi-degree-of-freedom system, a numerical procedure was employed to determine the response. While most engineering approaches to the design of such systems utilize a static approach, results from this research indicate that static analyses cannot effectively predict the behavior of a dynamic, damage-prone system. Most importantly, the rate of damage accumulation will have the greatest impact on the stability properties of the system. In fact, for certain load cases, a system that accrues more damage may be less prone to instability than a system that suffers little damage. For this research, it was assumed that damage caused a reduction in the stiffness such that the structure experienced cyclic softening with increased cycles of loading. Application of the results to seismic-resistant design was considered.National Science Foundation Grant CES 86-5801