| dc.description.abstract | The objective of this study is to optimize the isolation layer damping coefficient for basic seismic isolation structures and incorporate the Kanai-Tajimi filter to better account for the ground effects at various locations in Taiwan. The determination of parameters for the Kanai-Tajimi filter is based on Taiwan Seismic Design Code, ensuring that the ground acceleration generated by passing white noise through this filter matches the design response spectrum
specified in the seismic design code. Additionally, to ensure a more realistic analysis of the optimized design under seismic excitation, real earthquake records are also modified to match the design response spectra on different locations for time history analysis.The study focuses on the optimization of the isolation layer damping coefficient. The
damping coefficient is divided into an initial damping coefficient and a controlling damping coefficient. By rearranging the terms in equation of motion, the controlling damping force in the isolation layer can be treated as an active control force, transforming the optimization design
problem of the isolation layer damping coefficient into an optimization control problem of the active control gain matrix. Since this active control force is not full-state feedback, the study employs a direct output feedback method to find the optimal gain matrix. Traditionally, direct
output feedback methods require defining control force weightings, cause the quadratic performance index be influenced by these weightings. Therefore, the optimal value of the gain matrix is not the optimal damping coefficient of the isolation layer. However, when the control force weighting is zero, the gain matrix in direct output feedback is not easy to be solved. To figure out this problem, this study introduces a parameter iterative updating method that only requires selecting an appropriate control force weighting to obtain the gain matrix that includes the controlling damping coefficient. Following, the initial damping coefficient is updated iteratively until the gain matrix converges to zero, completing the optimization and obtaining the optimal design of the isolation layer damping force.
Finally, a multi-degree-of-freedom isolated system is established for the upper structure in Etabs. The floor parameters of the structure are therefore obtained and exported in matlab.Using the optimization method for the isolation layer damping coefficient mentioned above,
the study obtains the optimal damping coefficient for the isolation layer. Then, the optimized multi-degree-of-freedom isolated system is created in Etabs and subjected some ground accelerations. These ground accelerations contain the Kanai-Tajimi filter shaped white noise,the design response spectrum matched ground acceleration, and some notable real earthquake records. The time history analysis results confirm that the design of the optimal damping coefficient of the seismic isolation layer mentioned in this research has a good seismic isolation effect, which verify that the optimal damping ratio calculated by this optimization method is the best value to minimize the absolute acceleration response of the structure. | en_US |