Additional viscous dampers for civil structures: Analysis of design methods based on effective evaluation of modal damping ratios

摘要

Design methods for supplemental dampers aimed at reducing vibrations of civil structures often leave unanswered the following question: starting from the structural inherent damping, the adoption of supplemental dampers which level of damping can achieve? From this perspective, the paper shows a methodology based on the well known state-space representation of dynamical systems to calculate the modal damping ratios of non classicalon proportional damping schemes. The methodology is then adopted to analyse a number of design methods for supplemental damping systems found in the scientific literature. The analysis shows that many design methods yield a similar result of implicitly suggesting a 1 st modal damping ratio of about 20%. The same methodology is also adopted to show that the contribution of higher modes is generally negligible in designing a supplemental damping system and that the required damping level can be typically obtained with a limited number of supplemental devices.