Pounding Responses And Control Of Adjacent Structures Under Earthquakes

In modern cities, there are more and more large and high buildings, resulting in inadequate separation between adjacent buildings. Some of high-rise buildings are designed to be composed of several substructures because of functional application. When two closely spaced adjacent structures are subjected to strong earthquakes, collisions between them may occur. So the study on the effect of the seismic pounding between adjacent structures and the collision prevention measures is significant. In this dissertation, the following aspects are studied through theoretical and numerical analysis:(1) On the basis of Hertz theory of impact, a new improved Hertzdamp contact model for pounding simulation was proposed. Compared with other Hertz contact models, the proposed model is more reasonable, and the numerical results show higher precision of the model. Then the impact of base-isolated building with displacement-constraint devices, with non-isolated structures and with base-isolated structure under near-fault ground motions was investigated by comparative analysis. The results show that base-isolation still can reduce the seismic responses of superstructure when pounding occur, and pounding leads an obvious magnification of its acceleration. Through the comparative analysis, the number of impacts of base-isolated structure with both sides building is far more than with just one-side collide.(2) The application of explicit formulas of visco-elastic dampers between adjacent structures under earthquake excitation is investigated. Two control objectives are selected to minimize the vibration energy of the main structure and to minimize the vibration energy of both adjacent structures. The pseudo-excitation method is used to study the optimum parameters of visco-elastic dampers and the effect on the parameter values when the structural modal damping ratio and site condition change. The results show that changes of the structural modal damping ratio and site condition have little effect on the optimum parameters of visco-elastic dampers. The correction of the explicit formulas of visco-elastic dampers between two multi-degree-of-freedoms structures based on the first natural frequencies and the sum of mass of adjacent structures is further verified.(3) Optimal arrangement of viscoelastic dampers (VEDs) used to link two adjacent shear-type structures under seismic excitation was investigated. The two-step optimal design method was proposed. The results show that the higher is the number of the dampers, the smaller is the difference in the control effect between the optimal and the worst placements of dampers. Thus, the optimal placement of dampers is more important when fewer dampers are used. The placement of only one damper between two adjacent shear-type structures should be avoided; if more than one damper is used, they should be distributed on the top and lower floors of the structures. Optimization of the number of dampers had little effect on response reduction. The most important factor was the optimization of the placement of the dampers.(4) Seismic responses of two adjacent structures coupled with non-linear hysteretic dampers subjected to near-fault ground motions were investigated. The nonlinearity of the structure was characterized by the Bouc-Wen model. A series of near-fault earthquakes were simulated via the artificial synthetic method by the combination of a recorded earthquake (background ground motion) with equivalent velocity pulses. Extensive parametric studies were conducted to investigate the optimum yield force and yield displacement of non-linear hysteretic dampers. The performances of hysteretic dampers in terms of reducing structural responses were also investigated. The proper yield force and yield displacement have small differences as adjacent structures are under different near-fault earthquakes with different values of participation coefficient of equivalent velocity pulse. Using non-linear hysteretic dampers to connect adjacent inelastic structures can effectively mitigate earthquake-induced responses of adjacent structures.