Study Of Some Problems On Vibration-Reduction Control Of Engineering Structures

Vibration-reduction control of engineering is a new branch of research of the engineering vibration, and it is one of the hot subjects of studying in civil engineering too. Around the vibration-reduction of civil engineering, a lot of work was done in this thesis as follows:1 According to the problems facing the widely-used base-isolated system, a new pattern of isolated system, multi-isolated system, is presented and "the second isolation degree" is introduced. Regarding the earthquake waves as a smooth random process, the isolation effect of multi-isolation structure and it' s influential parameters are studied by using the theory of random vibration. Imitating the time history of wind loads with Monte Carlo method, the comfortableness of the base-isolation structure and the multi-isolation structure acted by wind loads is analyzed, and the impact related to isolation degree to whiplash of little superstructure is analyzed too. The results show that the multi-isolation structure can improve the anti-seismic performances of structure.2 Regarding the foundation as an isotropic elastic half space, the interaction of soil-structure(SSI) with rigid shallow basement is analyzed. Using the Penzien modle, the dynamic equations of pile-base are derived, and it' s SSI and influential parameters are analyzed. The research results show that the soil has a direct impact to isolated structure, which is much smaller than that on the non-isolated system.3 The composite isolated structure is presented for the first time, and the dynamic and control equation are derived. The control effect and the influential parameters of isolated structure are studied by using LQR and random optimal control method repectively. The results show that the composite isolated structure can achieve the expected control goal with small energy input.4. The thought of suppressing the vibration of structure with multi-partcomposite structure is put forward for the first time, the motion andcontrol equation is derived, and the effect of vibration-reduction andits influential parameters are studied. The results show thatmulti-part composite structure can suppress the vibration of each parteffectively.5 The schemes of strengthening the existing structures by using thecontrol theory and the isolation theory is put forward, and theireffectiveness is proved by examples.