| This dissertation deals with experimental and analytical studies related to seismic applications of viscoelastic (VE) dampers, a class of the major energy dissipation devices. It begins with a general overview of the development and applications of various energy dissipation devices. An analytical model for predicting the hysteretic behavior of VE dampers is then presented based on the Boltzmann's superposition principle, the method of reduced variables and data from damper tests. A feasibility study of using such devices in seismic strengthening of reinforced concrete structures was conducted on a 1/3-scale frame. After the frame was damaged in the laboratory under simulated strong earthquake ground motions, two sets of VE dampers were designed and implemented to the frame, and it was subjected to further simulated seismic excitations. Test results show that VE dampers are very effective in reducing seismic response of reinforced concrete structures. Finally, it addresses the effects of high damping to a structure which experiences larger inelastic deformation under seismic ground motions. Some shortcomings of using inelastic response spectra for design of energy dissipation devices are discussed and a new design method is then proposed based on the concept of damage control. In order to establish a rational design approach for everyday practice, an explicit procedure is developed to transform MDOF systems to equivalent SDOF models in the inelastic range so that evaluation of structural seismic performance can be easily carried out with and without the effects of added devices. A case study of using VE dampers in seismic retrofit of an existing 3-story reinforced concrete building is then carried out, in which dampers are designed at a prescribed damping ratio and refined until the overall damage index of the structure subjected to earthquake ground motions is reduced to an acceptable level. |
