Smart energy dissipation systems for protection of civil infrastructures from near-field earthquakes

The purpose of this research is to explore an effective control system for protection of structures from near-field ground motions. Based on the analysis of a large amount of recorded ground motions, an analytical model for the velocity pulse in nearfield ground motions is developed. The closed-form solution for an elastic SDOF structures subject to such a pulse model is derived. The performance of various passive dampers for structures subject to near-field ground motions is also investigated using the proposed pulse model. Further, an innovative hybrid control system is proposed to protect structures from strong ground motions based on an optimal polynomial controller. The hybrid control system consists of passive dampers and active (or semi-active) actuators installed in parallel with the passive dampers. The control force of the hybrid control system is determined using the optimal controller. The linear part of the optimal polynomial controller is proportional to the response of the structure and it can be implemented by active (semi-active) actuators or passive linear viscous dampers. The nonlinear part is a high order function of the states of the structure and it can be implemented by active actuators or semi-active dampers. The performance of the hybrid control system is illustrated by applying this control system to protect a SDOF structure and a Benchmark cable-stayed bridge from seismic excitations. Numerical results indicate that the hybrid control system is very effective in reducing the displacement of the structures for a broad spectrum of ground motions. Since the control force of the active or semi-active damper in the hybrid control system is naturally impulsive and is only required at a few instances during the entire seismic episode, this hybrid control system might be implemented easily and practically in the future. Furthermore, the proposed pulse model is also used to improve the performance of semi-active or active controllers by augmenting the structural system with the input shaping filter obtained from the pulse model. Numerical results demonstrate that a semi-active or active controller designed in such a manner is much more effective than passive viscous damper and active controller neglecting the ground motion information.