The Study On The Seismic Vibration Control Of Plan-asymmetric High-rise Buildings With Viscous And Viscoelastic Dampers

In this paper, a series of research is carried out on vibration control of plan-asymmetric high-rise buildings with passive energy dissipation dampers, which mainly includes seismic response analysis of tall buildings with dampers, performance-based design method for structures with dampers, and optimal distribution of dampers in asymmetric structures. The specific contents are as follows:(1) Parameter analysis of dampers. The influence of damper parameters on vibration of SDOF system is analyzed. Base on parameter analysis, comparison is made between viscous and viscoelastic dampers' influence on modal parameters of asymmetric one-storey structure and vibration reduction effect.(2) Improved Ritz method to analyze seismic response of tall building with non-classical damping. Improved Ritz Method adopts not only load dependent Ritz vectors but also frequency dependent Ritz vectors. Both vectors are generated by Lanczos Algorithm in which the frequency dependent Ritz vectors can be obtained after eigenvalue shift with square of the predominant excitation frequency. A linear transformation is made to the dynamic equation by using the Ritz vectors and then the pseudo-force method is employed to solve the coupled equation after transformation.(3) Performance-based design method for structures with energy dissipation devices. This paper advances two performance-based design methods:â‘ Direct displacement-based seismic design method with performance target expressed by storey drift. MDOF structure is transferred to SDOF system. And the required total damping ratio of SDOF system to satisfy displacement demand for given earthquake wave is evaluated through displacement spectrum, which can be taken as the approximation of MDOF structure's damping ratio demanded to meet performance requirement. Then the supplemental equivalent damping ratio and the corresponding damping coefficients of dampers are determined. Direct displacement-based design method can only be applied to symmetric structuresâ‘¡Multimode-based design method for buildings with dissipation devices. The performance index of structures is expressed by multi-mode. By introducing maximum displacement ratio of modes' equivalent SDOF systems, the structure performance index can be represented as a function of maximum displacement of the first mode SDOF system. Then, the allowed maximum displacement of the first mode SDOF system can be calculated from the given performance target. The damping ratio demanded by the first mode can be identified from the displacement spectrum, and the supplemental damping ratio and the damping coefficients are determined. After that, the equivalent damping ratios supplied by the damping coefficients for other modes are calculated, and then the maximum displacement ratio and the correlation coefficients between modes are revised accordingly. Iteration calculation continues until the first mode damping ratio meets the precision requirement. The damping coefficients for the structure can be calculated from the convergent damping ratio. Multimode-based method can be applied not only to asymmetric structures but also to symmetric structures.(4) Optimal distribution of dampers. A single-storey asymmetric structure is employed as the simplified model of plan-asymmetric multi-storey structures to study the optimal plan distribution of viscous and viscoelastic dampers. Based on the random vibration theory, the objective function is expressed as a function of damper eccentricity. The optimum damper eccentricity is found by minimizing the target function with the optimization toolbox of MATLAB. Then, parametric analysis is carried out on the optimum damper eccentricity. It is concluded that there are too many factors influencing the optimal eccentricity of damper to calculate it precisely in practice. So the sensitivity of objective function to damper eccentricity is analyzed and the approximate optimal damper eccentricity is proposed. The Sequential Search Algorithm is employed to optimize the distribution of damper coefficients between different storeys, and the plan distribution of damper coefficients in every storey is in accordance with the approximately optimal eccentricity. The distribution of viscous dampers is optimized by the proposed method and GA algorithm respectively, and comparison of the seismic response reduction effect shows that the proposed method can get favorable result in relatively shorter time and is an effective method for the optimal distribution of dampers. (5) At last the theoretical methods are applied to an actual project.