Seismic Design of Passive Tuned Mass Damper and Base Isolation Using Active Control Algorithms

• Main Authors: Syuan Shia, 夏瑄
• Other Authors: Chia-Ming Chang
• Format: Others
• Language: en_US
• Published: 2017
• Online Access: http://ndltd.ncl.edu.tw/handle/vk9nw5

碩士 === 國立臺灣大學 === 土木工程學研究所 === 105 === Seismic isolation and tuned mass damper (TMD) have been widely accepted as a passive control strategy for protection of structures. A base-isolated building employs a flexible element underneath the structure that shifts the fundamental frequency of the building away from the dominant frequencies of earthquakes. Due to the fact that the flexible element can introduce excessive displacements at base during severe earthquakes, additional viscous damping devices are recommended to be installed along with the isolation layer in most seismic design codes. On the other hand, a TMD system consists of a mass, spring, and damping device with a tuned frequency, thus the response of the structure can be regulated by the effect of resonance. In tall buildings, TMD is usually employed to reduce structural responses against strong winds and earthquakes. Therefore, the objective of this study is to develop new design procedures for base-isolated buildings and buildings with a tuned mass damper. In these design procedures, both stiffness and damping are concurrently determined using the feedback control algorithm, e.g., the linear quadratic regulator (LQR) control algorithm or linear quadratic Gaussian control algorithm. In the seismic isolation design procedure, the mass, damping, and stiffness of a superstructure is assumed to be known, and a mass ratio between the superstructure and isolation layer is predetermined. The stiffness and damping coefficient of the base isolation can be obtained by the LQR control algorithm, while these two terms vary with the weighting selected in LQR. To determine the most appropriate stiffness and damping, a performance curve is generated in terms of maximum time- or frequency-domain responses. Note that the time-domain responses are obtained when the isolated building is subjected to spectrum-compatible ground motions. Subsequently, the stiffness and partial damping coefficient are achieved by lead-rubber bearings, while the remaining damping coefficient is realized by additional viscous dampers. Moreover, the detailed design of lead-rubber bearings is parameterized by a bi-linear model, consisting of the designed stiffness, damping coefficient, pre-to-post yielding stiffness ratio, and a target displacement. In the TMD design procedure, the mass, damping, and stiffness of a primary structure is assumed to be known, and a mass ratio between the primary structure and TMD is predetermined. The stiffness and damping coefficient of the TMD can be obtained by the feedback control algorithm in accordance with different control objectives, and these two terms can be realized by varying the weightings selected in the control algorithm. Then, the maximum poles in transfer functions are employed to determine the most appropriate parameters, which result in the minimum poles among a number of transfer functions. Consequently, the optimal natural frequency and damping ratio of TMD system are achieved. In this study, several numerical examples are carried out to demonstrate the proposed design procedures. Moreover, the numerical study also examines various sets of optimum parameters in different scenarios. As shown in the simulation results, the seismic isolation and TMD design procedures are quite effective for buildings against earthquakes.