Study On Seismic Performance And Fragility Analysis Of Existing Concrete Frames Upgraded By Metallic Dampers

There are a large number of exciting reinforced concrete frames in China.Most of them are badly short of seismic reserve capacity due to the aging of materials or not meeting the existing design requirements.The traditional reinforcement methods only dissipate energy through the deformation and the damage of components,which has a great impact on itself.Energy dissipation and shock absorption reinforcement can dissipate most of the seismic energy,greatly reduce the dynamic response of the structure under the earthquake action,and effectively improve the seismic performance of the structures,which has become a vigorously promoted method for improving the seismic performance of the structure in our country and overseas.As a common device in energy dissipation and shock absorption reinforcement methods,the shear metallic yielding damper has the advantages of flexible layout,small volume and load-dissipation coupling function.However,it’s often unable to exert the best energy dissipation capacity because it is prone to out-of-plane buckling.Besides,when capacity of the metal dampers could not match the structures,the metallic dampers consume little energy or the energy consumption capacity of the them cannot be fully played,resulting in the inability to coordination between the structures and the metallic dampers.Nowadays,there is a lack of seismic tests studies and theoretical analysis of metallic damper upgraded existing concrete frames.Therefore,the shear-bending yielding coupling damper was proposed to upgraded the existing concrete frames in this dissertation.In order to make clear the design method,seismic performance and seismic vulnerability,some work was carried out :(1)According to the engineering situation,A novel shear-bending yielding coupling damper and the connection between damper and existing frame were developed.A practical design method based on shear ratio was proposed,and the prototype structures of 4-,6-and 9-story and corresponding reinforced structures were designed,respectively.Based on fiber model theory and existing tests,finite element models of prototype structures and reinforced structures were established by Open Sees.The accuracy of damper model and empty frame model was verified respectively,which was provided theoretical support for subsequent dynamic test model and numerical analysis.(2)An empty frame and a frame upgraded by metallic damper were carried out by hybrid dynamic test method.The failure modes of specimens under FOE,DBE and MCE were investigated,and the accuracy of simulation models established by Open Sees were verified.The structural displacement,shear time curves,hysteresis characteristics,overall response,energy consumption were analyzed.The hysteretic curves,skeleton curves,stiffness degradation,ductility and energy dissipation of specimens under quasi-static loading were studied.The influence of metallic dampers on the seismic performance of existing frames were revealed.(3)The reliability of the design method based on shear ratio was verified in terms of inter-story drift,residual inter-story drift and metal damper displacement ductility by a large number of nonlinear time history analyses for typical structures with 4-,6-and 9-story.On the basis,taking the seismic shear ratio of the damper to the structure as the analysis parameter,the variation of the maximum inter-story drift,the additional axial force of the beam and column and the hysteretic energy dissipation of the damper with the shear ratio were studied,and the optimized range of shear ratio was obtained.(4)Based on IDA method,the non-collapse seismic vulnerability analysis of concrete frame structures upgraded by metallic dampers were carried out,and the damage transcendence probability of existing frames and upgraded frames under different seismic vibrations was obtained.The failure situations of them were also analyzed under noncollapse.Basing on this circumstance,the collapse seismic vulnerability analysis was carried out,and the collapse resistance of the them was analyzed by relevant collapse resistance assessment methods.The collapse resistance of them was evaluated.