Fluid Viscous dampers are added to building to protect its structural, nonstructural components, and contents. Dampers are designed to resist forces produced by the maximum considered earthquake. The efficacy of dampers in providing seismic protection and the code-prescribed methodology for design of these units have been well established and have been validated by the excellent performance of buildings with dampers in the past earthquakes. However, little data is available for buildings with viscous dampers subjected to large earthquakes. A multi-year research project is currently investigating such cases. Initial analyses revealed that the limit states of viscous dampers have a significant effect on the response of the building to which they are installed. Analytical model of steel buildings with viscous dampers, incorporating damper limit states, have been prepared and subjected to incremental dynamic analysis to determine the collapse performance. To date, analysis has shown that performance of the buildings with
viscous dampers was acceptable when subjected to large earthquake. Furthermore, the use of factors of safety to delay the onset of reaching limit states was seen to be both beneficial and cost effective.