Fluid Viscous Dampers

This article summarizes the extensive viscous dampers investigation performed by NCEER at State University of New York, Buffalo Campus. This included computer modeling of both the dampers and complete isolated systems, along with shake table testing and correlation of results. The article also describes a very large damper projects; dampers + base isolation for a set of five hospital buildings near San Bernardino, CA.

This 206 page report presents the results of an extensive study on fluid viscous dampers. A series of component tests with various dynamic inputs was performed to determine the mechanical characteristics and frequency dependencies of the dampers. In addition, temperature dependencies were evaluated by varying the ambient temperature of the damper during component testing. Based on these component tests, a mathematical model was developed to describe the macroscopic behavior of the damper. Earthquake simulation tests were then performed on one story and three story steel structures both with and without dampers. The addition of supplemental dampers significantly reduced the response of the structure for both interstory drift and shear forces. The experimental responses correlated well with analytical predictions.

This paper presents a review of supplemental damping devices used for the control of the seismic response of structures. The mechanical properties of these devices are discussed and considerations in the design of energy absorbing systems are presented. Conventional structures passively resist earthquakes through a combination of strength, deformability and energy absorption. They have very little damping, so elastic energy absorption is small. Strong earthquakes deform these structures well beyond their elastic limit through localized plastic hinging, which results in increased flexibility and energy dissipation. Most of the earthquake energy is absorbed by the structure through localized damage of the lateral force resisting system. This is somewhat of a paradox in that the effects of earthquakes (i.e. structural damage) are counteracted by allowing structural damage. Structural performance can be greatly improved if a large portion of the input energy can be absorbed, not by the structure itself, but by some type of supplemental device. This paper describes a number of ways to do this, including friction devices, yielding metal systems, elastomeric viscoelastic dampers and fluid viscous dampers.