Studies On Seismic Behavior Comparison And Optimal Design Of Displacement-based And Velocity-based Dampers

Passive energy dissipation structures have advantages of definite damping mechanism, effective reduction of structural response, safety and reliability. So over thirty years, studies on experiments, theoretical analyses and design methods of various energy dissipation devices have made great development. The technique of passive energy dissipation has been widely applied in seismic control of new constructions and reinforcement of seismic damage structures and has extensive forms. At present, contents related to passive energy dissipation have been written into the China Seismic Code (GB50011-2001). Among it, the use of displacement-based dampers and velocity-based dampers is the technology needed to be emphasized and popularized. But for a variety of forms and different requirement of the projects, how to choose suitable type of dampers and design dampers optimally will affect the development of the technology during its popularization, which has important realistic meaning and is worth of further study. The thesis focuses on seismic behavior comparison and optimal design of different dampers, and the following aspects are devoted to the main effects:(1) Considering different computation models, comparison of the nonlinear vibration control of high-rise structures with additional two type passive dampers is done. For the current problem of storey shear-bending model in elasto-plastic analysis, approximate treatment is done to the stiffness matrix. Designing storey shearing model structure from shear-bending model structure according to dynamically equivalent standard, time-history analysis programs of structures are compiled. On the premise that the equivalent damping of two kind dampers is equal, studies focus on the effect of type and quantity of dampers on structure control effectiveness of different computation models and comparisons are done. The numerical analysis results show that the two types of dampers' control effectiveness are different for the high-rise structure of different computation models. Suggestions are proposed that when using passive energy dissipation technology, different type of passive dampers should be chosen to control vibration responses according to the structure analysis model.(2) A new objective function of dampers' location optimization is proposed. As the China Codes have given certain limit to the structure's drift angle, maximum acceleration and maximum horizontal displacement of vertical components, three structure indexes are comprehensively considered in the new objective function. Various coefficient combinations of indexes can be chosen according to the different requirement of structural security and coziness. On the premise that the number of dampers is fixed, it is dealt with the optimal placement of displacement-based dampers for several building models with different number of stores and seismic ground motions at four types of sites using genetic algorithm. Five kinds of combination modes of the three indices in optimal function are then supposed. Nonlinear step-by-step time history analyses are carried out to achieve the optimal combination mode of the coefficients in mathematic model and the optimal locations of these dampers for several building structures. The optimal results can also verify effectiveness and feasibility of the new objective function for structural control and some meaningful suggestions about optimal placement of displacement-based dampers are given.(3) Two estimating indices are presented to assess the structural responses with different optimal placement of dampers. Using the new objective function, the optimal locations of two types of dampers are analyzed for several building models with different number of stores and seismic ground motions at four types of sites. Two estimating indices are utilized to assess the response to the optimal location under the condition of five combination modes, which can generally express the best response control and the propositional combination of the coefficients is available under different conditions. Comparison of two kinds dampers' optimal results show that the objective function of location optimization are different for different structures with different dampers and some conclusions for application are given.(4) The displacement-based seismic design method has been applied to the dampers design utilized in new constructions and reinforcement of seismic damage structures. Because of the inconsequence of target displacement formula of multiple-degree of freedom system used for high-rise structures, a modified displacement formula is suggested, which can establish the relationship between the target displacement and the performance indexes. Taking a target displacement of a certain security grading structure as the known condition, and the energy dissipation devices as unknown conditions, according to the equivalent stiffness and damping formulas, the reverse calculation of the equivalent single degree of freedom system was done to gain the design parameters of different types of dampers expected to meet performance targets. The numerical analysis of a high-rise steel structure as an example shows that using this method to design dampers can meet the prospective performance targets, and it is a simple and practical design means.(5) With the international common performance evaluation platform of structural vibration control—the third stage of Benchmark three models, using Benchmark performance evaluation indices of nonlinear vibration control, the control results for displacement-based and velocity-based dampers were compared. Combining the passive control of structures with the modern control theory, using MATLAB/SIMULINK to establish simulation models of the structures with displacement-based and velocity-based dampers, the responses of three Benchmark structure models were calculated under far and near-field earthquakes. Control effectiveness is compared for different types of dampers on different structures through different evaluation indices, which can provide a certain criterion of reference for the application and design of the passive energy dissipation dampers.