This paper presents preliminary results of a study on a full-scale 5 story steel frame with added viscoelastic (VE) dampers. Two types VE dampers with distinctly different properties are installed in the structure in the East-Western (EW) and North-Southern (NS) directions, respectively. Test results show that under ambient vibrations, the increase of damping in the full-scale structure is not obvious because of the small input energy. Under free vibration tests and the small earthquake ground motion, the increase of damping in the EW direction, which was installed with 3MISD110 VE dampers, is more significant. These dampers, however, have not performed as expected due to the lack of damper deformation. Analytical results show that the modal strain energy method which has been validated by extensive shaking table tests on small scaled models can not accurately predict the damping ratios of the full scale structure in this study. The reasons of insufficient accuracy on damping ratio prediction, including causes such as the relatively small earthquake, the improper connection details, the relatively thin gusset plates used, etc., are currently under investigation. In addition to providing important data base for verifying the effectiveness of applying the VE damper to full-scale structure, this study will learn important experience concerning the implementation and detained design of damper connections for practical applications.
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