Dynamic Analysis Of Composite Isolation Structure Under Near-fault Pulse-like Ground Motions

In recent years, base-isolated technology has been widely applied. Base-isolation structure sets up the isolation layer which generates a larger deformation. Base-isolation structure's vibration period has increased and seismic response of superstructure has reduced. Base-isolated structure shows excellent effect in reducing the damage under far-field ground motions, however, it may cause damage under near-fault pulse-like ground motions which have long-period velocity and displacement pulses. MR damper is one of excellent semi-active control devices, it combines base-isolation structure to form intelligent and composite isolated system. The system can adjust damper's parameters in real time according to structural response in order to reducing the damage resulted from the ground motion. It has become very promising isolation system in civil engineering.The main contents of this thesis as below:(1) The near-fault ground motions are simulated by combining E1-Centro ground motions with equivalent pulse motions. A method to artificially generating near-fault pulse-like ground motions is given. By the method, synthetic seismic waves are obtained.(2) The dynamical equation is established for base-isolated structure, viscous damper combining base-isolated structure, intelligent and composite isolation structure under ground motions. Inputting artificially generating near-fault pulse-like ground motions, seismic responses of no controlled structure (base-fixed structure) and the previous structures are analyzed by Runge-Kutta method.(3) The relative displacement response, acceleration response, story drift and maximum story shear force are analyzed and contrasted for four structures. By comparing example results, the isolation effect of base-isolated structure has been weakened under near-fault pulse-like ground motions. After appending dampers, the seismic response of isolated structure will reduce obviously. Intelligent and composite isolation structure's seismic response is the smallest and the structure is the most effective in reducing the damage from ground motions. (4) Intelligent and semi-active control structure adopts two different methods. The structure has a better isolation result and different dynamic response when using different control methods. By selecting and adjusting right semi-active control strategy, we can get a satisfactory and optimal isolation control result.