The Nested-Eccentric-Shells Damper with an Improved Approach to Increasing Hysteresis Behavior

By the concept of control structures a new shell configuration for a steel energy dissipative device designed for earthquake protection of structures is proposed in this study. This device is named a nested-eccentric-shells damper (NESD). This device is made of a large cylindrical shell that surrounded three small cylindrical shells. The conventional methods of welding or metal casting can be applied in constructing this damper. The configuration of the shell-type components is designed in such a way that to be able as a combination of series and parallel springs. To assess the performance of this damper, numerical analysis and full-scale testing are run. Hysteretic loops obtained from the analysis with highly ductile performance are applied to determine the behavior of this proposed damper. The results indicate that the nested-eccentric-shells damper is of a stable behavior in hysteretic loops, and can provide appropriate damped energy subject to cyclic loading. However, in order to improve the performance and interaction of the internal members of this damper, a thickness ratio is proposed for the inner shells and the usefulness of using this modification in numerical analysis has been proven in this study.