Seismic Performance Evaluation Of Damaged Frame Retrofitted With Self-Centering And Energy-Dissipating Rocking Wall

This thesis proposes the novel concept of retrofitting damaged reinforced concrete frame with self-centering and energy-dissipating rocking wall.This study establishes the accurate model of a three-bay frame using general purpose finite element analysis software ABAQUS and data from an existing experiment.Pushover analysis were then performed to identify the individual contribution and the combined effects of rocking wall and its combination with post-tension and shear-type damper on the performances of the damaged structure after retrofit.The results indicated that the rocking wall acted similarly to a shear wall before the rocking starts and contribute significantly to the initial lateral stiffness of the wall.Parametric analysis of the rocking wall thickness indicated that there is a linear relationship between the wall thickness and the initial stiffness of the retrofitted system.The deformation mode of the frame is also closely related to the thickness of the rocking wall,it is discovered that the thicker the wall,the more uniform the inter-story deformation patterns are.However,the wall thickness has little impact on the retrofitted system once the wall rocking starts.The addition of post-tension tendon to the rocking wall system enables the wall to self-center and increase lateral stiffness and bearing capacity of the retrofitted system.When the shear-type damper is installed,the energy dissipation of the system is increased.The stiffness and bearing capacity of the retrofitted system are also improved.In the time-history analysis,the model of an existing,full-scale6 story reinforced concrete frame is adopted.Five earthquake records were selected according to the characteristics of the site.The peak ground acceleration(PGA)of the earthquake records are adjusted to match the definitions of frequent and rare earthquakes as per Chinese Standard.The earthquake record which causes the seismic response of frame to exceed its design limits are selected in subsequent analysis.It is found that the thickness of the rocking wall is directly related to the maximum inter-story drift and the distribution of inter-story drift of the frame.As the thickness of the wall increase,the maximum inter-story drift of the frame decrease and the distribution of inter-story drift become more uniform.As the post-tension is added to the system,the maximum interstory drift under rare earthquake excitation improved significantly whereas the maximum inter-story drift remain the same under frequent earthquake excitation.The distribution of inter-story drift under rare earthquake is further improved.With the addition of sheartype dampers,the overall drift magnitude of the retrofitted system is fundamentally decreased as the dampers dissipate energy under earthquake excitations.The seismic response of the damaged frame retrofitted using rocking wall in combination with posttension and shear-type damper fall within the relevant design limits.The soft-story mechanism is effectively mitigated through the rocking wall retrofit of the damaged structures.The results of pushover analysis demonstrated that the stiffness and bearing capacity of the retrofitted system have been restored to its intact state.