Identification and Modeling of Limit States of Viscous Dampers under Large Earthquakes

Fluid viscous dampers have been extensively used in new construction and seismic retrofit. They provide a reliable mean of dissipating seismic energy. In practice, the dampers are designed and sized using the procedures outlined on ASCE 7 for new structures and ASCE 41 for retrofit of existing buildings. These guidelines provide a factor of safety for damper design. In typical applications, the engineers analyze structures with dampers without consideration for the damper limit states and instead count on the abovementioned safety margins. However, the limit states of viscous dampers have a significant effect on the response of the building to which they are attached to. To address this issue, a refined model of viscous dampers has been developed based on the force-displacement-velocity constitutive relations of the damper components and incorporating the damper limit states. The model incorporates both displacement and force limit states. Simulations were conducted to check the limit state activation for the model. Experimental data were then used to verify the accuracy of such limit states. Finally, a sample structure was analyzed to assess the effect of limit states on the building response and to evaluate the safety margins.