Research On Damping Performance And Improving Design Measures Of Rc Frame Structure With Base-isolated

The base-isolated structure is widely used in residential,school,hospital and other projects in high-intensity areas due to its good earthquake resistant performance.Both the engineering practice and the actual earthquake damage experience show that the current isolation design method—“the partial design method” can basically meet the fortification target of the rare earthquake.However,this method still has some problems such as The difference between the calculation assumption and the actual situation is large,and the systematic research on the influencing factors of the seismic isolation effect of the isolated structure is less.At the same time,the introduction of the extremely rare earthquake in the fifth-generation China's ground motion parameter zoning map indicates that China has put forward higher requirements for the performance of construction projects.In-depth analysis and evaluation of the seismic performance of the isolated structure under extremely rare earthquakes is required.The RC frame structure is flexible in layout and is a commonly used type of isolated building.Therefore,this paper takes the RC framework structure as the research object,the main research work is as follows:(1)Based on a RC frame structure with base-isolated,three sets of 12 elastic finite element models were established to study the influence of the period ratio and equivalent damping ratio of the isolated structure on its earthquake resistant performance.Research shows that increasing the period ratio and the equivalent damping ratio of the isolated structure can improve its earthquake resistant performance,but the damping rate decreases with the increase of the period before before the structure is isolated.The numerical relationship between the damping coefficient and the period ratio and the equivalent damping ratio of the isolated structure is fitted to provide a reference for the design of isolation engineering.(2)Select the three typical model in(1),use PERFORM-3D software to establish its overall three-dimensional fine finite element model with isolation layer,and input the acceleration time-history curve corresponding to extremely rare earthquake for elastoplastic analysis to study on seismic performance from lateral migration,interlaminar shear force,plasticity development of components and energy consumption.The results show that the3-layer isolated model meets the “Repairable under the extremely rare earthquake”fortification target,and the 6-layer isolated model meets the “life safety” performance level.For the 9-story isolated model,the structure above the isolation layer is no longer a rigid translation,and the plasticity of the bottom floor is higher.The displacement angle between the layers on the bottom floor of the model is more than 1/100,which is weaker and needs to be strengthened.(3)Based on the research results of(2),there are some defects in the bottom-floor damage of the base-isolated RC frame structure under the action of the extremely rare earthquakes.Two improvement measures,the response spectrum design method based on actual vibration mode of isolated structure and based on the partial design method and design enhancement of the bottom floor are proposed,establish a finite element model of the basic isolation RC frame structure improvement scheme and perform time history analysis.The results shows that the inter-layer displacement angle of upper frame structure of the improved models is not over 1/100,and the energy consumption mechanism is more reasonable.The performance level of the structural members is about one level higher than the original structure,which can meet the performance requirements of the extremely rare earthquake levels.