Elasto-plastic Analysis And Optimal Design Of Structure Restored By Viscoelastic Dampers Considering Earthquake Damage

Energy dissipation reinforcement is an important method of structural restoration and enhancement.This method is able to change structural dynamic characteristics and improve structural seismic resistance by adding energy dissipation devices to structures.As a common energy dissipation device,viscoelastic damper has advantages such as good dissipation effect,small construction difficulty and low cost,which contribute to its extensive use in engineering.The subject of this dissertation is earthquake-damaged structures restored by viscoelastic dampers.Overall and deep research on this subject starts from the performance degradation rules of damaged members.Resilience model of damaged RC members based on statistical comprehensive performance degradation is built.Using this resilience model,the modeling and elasto-plastic analyses of earthquake-damaged structures restored by viscoelastic dampers are achieved.At last,a parameter optimization algorithm and a layout optimization algorithm of viscoelastic dampers are developed on MATLAB-OpenSEES joint platform.The optimal design of structure restored by viscoelastic dampers considering earthquake damage can be solved by using these two algorithms.The main research work and contents are as follows:1)To quantify the performance degradation degree of damaged members,strength degradation index αM,stiffness degradation index aK and dissipation capacity degradation index αγ are defined from the aspects of backbone curve and hysteretic rule.Regression analyses using cyclic loading experiment data of many members from SPD database are carried out.The resilience model of damaged RC members based on statistical comprehensive performance degradation is built.Cyclic loading of four RC members under damaged states are simulated.The simulation results fit well with the experiment results,which verifies the resilience model.Lastly Park-Ang damage index D is replaced by Kunnath damage index D’ and the analyses are redone.Then the pros and cons of two results are compared.2)Modeling of earthquake-damaged structures is achieved by using the resilience model of damaged RC members based on statistical comprehensive performance degradation.Combined seismic waves are applied to the intact structural model of a 5-floor plane frame while single seismic waves are applied to the damaged structural model.The results of two elasto-plastic analyses are compared to show that the modeling method is correct.A practical modeling method of earthquakedamaged structures based on physical damage is proposed by combining the former modeling method with Park’s classification of damage level.An 8-floor plane frame in three different damage states is modeled and elasto-plastic analyses are carried out.Viscoelastic dampers are simulated according Kelvin model in OpenSEES and elasto-plastic analyses of structure restored by viscoelastic dampers considering earthquake damage are finished lastly.3)A parameter optimization algorithm and a layout optimization algorithm of viscoelastic dampers is developed based on MATLAB-OpenSEES joint platform.The former algorithm can realize the optimal distribution of the total equivalent stiffness Kd in floors and obtain the Cθ-Kd curve of earthquake-damaged structure.The latter algorithm can solve the optimal layout of a fixed number of viscoelastic dampers with same specification in vertical structure.Combining these two algorithms,the process of optimal design of structure restored by viscoelastic dampers considering earthquake damage is proposed.An 11-floor earthquake-damaged frame is taken as example of optimal design.Lastly,deep research on the objective function of layout optimization algorithm is carried out.The influence of the weight coefficients value on optimization results is studied.An improved objective function based on the control rates is proposed and then tested effective.The innovations of this dissertation lay in:1)After defining the indices which can quantify the performance degradation degree,the resilience model of damaged RC members based on statistical comprehensive performance degradation is built by regression analyses.Modeling and elasto-plastic analyses of earthquakedamaged structures using the resilience model has accuracy and convenience combined.2)A parameter optimization algorithm and a layout optimization algorithm of viscoelastic dampers is developed based on MATLAB-OpenSEES joint platform.It makes full use of numerical calculation advantages of MATLAB and elasto-plastic analysis function of OpenSEES.Using these two algorithms,the optimal design of earthquake-damaged structures restored by viscoelastic dampers can be achieved.