An Analysis Of The Effect Of VE Dampers And Braces's Stiffness On A RC Frame Building Retrofit

Seismic retrofit using supplemental energy dissipation devices is a new seismic retrofit approach, which has many advantages over conventional retrofit approaches and will be of more application in the future.In this investigation, the focus is put on the effect of viscoelastic dampers and braces' stiffness on the seismic performance and responses to excitation of a RC frame building,which is retrofitted with viscoelastic(VE) dampers and their braces,modelld 3-dimensionally and analysed with the fast nonlinear analysis(FNA) method in the program SAP2000 that has been expatiated on in the thesis.Two ratios are developed in order to make the investigation.One of the two ratios is the one of the global horizontal stiffness of the braces to the shear stiffness of the undamped RC frame building at floor level i,which is assumed to be equal to the ones at all other floor levels,called the braces-stucture's ratio of stiffness and represented by the symbol a .The other of the two ratios is the one of the global horizontal stiffness of the VE dampers to the shear stiffness of the undamped RC frame building at floor level i,which is also assumed to be equal to the ones at all other floor levels, called the VE dampers-stucture's ratio of stiffness and represented by the symbol.In this research,combinations ofa =0.30 and 12 s are considered which form 12 cases of the RC frame building retrofit.On the basis of numerical analysis results of 12 cases of the model,rules on how the seismic performance and responses to excitation of the example change with the ratio is concluded. Subsequently,an optimal and one of many optimal retrofit schemes are attained.The optimal ratio means that the RC frame building will performed well under earthquake of seismic fortification intensity when it is retrofitted with VE dampers of the optimal ratio and braces of a =0.30, the VE dampers and their braces are placed as the thesis has described and some . columns of the RC frame building are strengthened.The optimal retrofit scheme is associated with the optimal ratio.In this investigation,the retrofit approachusing VE dampers and their braces has proved its prominent advantages over conventional retrofit approaches.Ulteriorly,an ideal range of the ratio, of the braces-stucture's ratio of stiffness,a, to the VE dampers-stucture's ratio of stiffness, is obtained,which may be used as a reference in other retrofits.In this investigation,a phenomenon is found that additional axial forces,which are in excess of members' carrying capability, are introduced into some columns which are connected to the VE dampers and their braces because of stress concentration. These columns should be an important consideration in the retrofit of existing frame buildings and specially strengthened adequately because it is impossible to make them meet their carrying capability by changing the stiffness of VE dampers and their braces.