ViscousDamper Material

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This command is used to construct a ViscousDamper material, which represents the Maxwell Model (linear spring and nonlinear dashpot in series). The ViscousDamper material simulates the hysteretic response of viscous dampers.

uniaxialMaterial ViscousDamper $matTag $K $Cd $alpha

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$matTag	integer tag identifying material
$K	Elastic stiffness of linear spring (to model the axial flexibility of a viscous damper (brace and damper portion)
$Cd	Viscous parameter of damper
$alpha	Viscous damper exponent

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Examples:

1. Input parameters:

Assume a viscous damper with axial stiffness K=300.0kN/mm, viscous parameter Cd=280.3kN(s/mm)0.3, and exponent a=0.30.

The input parameters for the material should be as follows:

uniaxialMaterial ViscousDamper 1 300 280.3 0.30

Using these properties, Figure 1 shows the hysteretic response of this damper for sinusoidal displacement increments of 12, 24 and 36mm and a frequency f = 0.5Hz.

The sensitivity of the viscous damper with respect to its axial stiffness is shown in Figures 2 to 4 for the following set of parameters:

Viscous Damper with various input parameter variations

2. Single story single bay frame with viscous damper

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References:

[1]	Oohara, K., and Kasai, K. (2002), “Time-History Analysis Models for Nonlinear Viscous Dampers”, Proc. Structural Engineers World Congress (SEWC), Yokohama, JAPAN, CD-ROM, T2-2-b-3 (in Japanese).
[2]	Kasai K, Oohara K. “Algorithm and Computer Code To Simulate Response of Nonlinear Viscous Damper” Passively Controlled Structure Symposium 2001, Yokohama, Japan (in Japanese).

Code Developed by : Prof. Kazuhiko Kasai (Tokyo Institute of Technology) and implemented by Sarven Akcelyan & Prof. Dimitrios G. Lignos, (McGill University)