Research On Biaxial Shear And Anticollision In Seismic Isolation Of Existing Buildings

Along with the occurrence of the great number of the irregular structure and the adjacent structure, there are two problems in isolation and reinforcement of these structure:l.The irregular structure suffer from biaxial shear forces under the earthquake which cause isolation bearing suffer from biaxial shear forces, therefore, isolation bearing shows the other constitutive relation that completely different from the constitutive relation under uniaxial shear force, and it is hard to get the reasonable and effective result by the original uniaxial analysis method.2.1t will increase the collision probability when reinforcing the adjacent buildings with small width of seismic joint, thus, this dissertation uses viscous dampers connecting adjacent isolation building to control the dynamic response under earthquake, avoiding the collision between the adjacent isolation building that endanger the safety of the structure.In this dissertation, the bidirectional load levelling device is used to test the lead rubber bearing of LRB300 and LRB400 under horizontal biaxial shear of low cycle fatigue load, and the test data of the lead rubber bearing in horizontal biaxial 1:1 shear deformation is obtained, then horizontal stiffness and equivalent viscous damping ratio calculated from the test data were compared. The test results show that:with the increase of the shear deformation, the horizontal stiffness and equivalent viscous damping ratio of lead rubber bearing are on the decline, in addition, when occurs the same horizontal shear deformation, the horizontal stiffness and equivalent viscous damping ratio of lead rubber bearing in biaxial shear forces condition are less than unixial shear force condition.In order to explore the effect that bidirectional nonlinear characteristics of the lead rubber bearing on dynamic response of eccentric structure, this dissertation also uses structure analysis software to analysis the structure related engineering example of elastic time history analysis under frequently occurred earthquake and the elastic-plastic time history analysis under fortification earthquakes as well as rarely occurred earthquake, discussing the impact of the lead rubber bearing bidirectional nonlinear characteristics on the dynamic response of eccentric structure. The analysis results show that:the dynamic response of base-isolated structure is larger when without consideration for bidirectional nonlinear characteristics of the lead rubber bearing, but ignoring the biaxial coupling will underestimate the deformation of lead rubber isolation bearing, which will be unsafe to the structures that have higher limit requirements for the horizontal displacement of isolation layer.To explore the dynamic response of the adjacent structure connected by the viscous dampers, this dissertation also respectively analyses the elastic time history analysis under frequently occurred earthquake and the elastic-plastic time history analysis under rarely occurred earthquake of adjacent structure connected by the viscous dampers. Ensuring that adjacent structure do not collide and setting the minimum shear force of he adjacent isolation structure as well as the smaller damper output as the goal, the enumeration method is adopted to seek out the optimal damping coefficient and damper layout position, and the effect of damper parameters and layout position on the dynamic response of the adjacent structure is discussed. Analysis results show that the application of the appropriate damper parameters and layout position can efficiently control top of the adjacent structure relative displacement under seismic action, which avoid the collision and ensure the safety of the structure in the earthquake.