Maxwell 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 Maxwell material simulates the hysteretic response of viscous dampers.

uniaxialMaterial ViscousDamper $matTag $K $Cd $alpha

$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

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:
[[File:ViscousDamperFig.pdf|600px|thumb|left| Viscous Damper with various input parameter variations]
2. Tcl input file for Viscous Damper Calibration.
3. OpenSees Example of 1-story steel moment frame with a viscous damper: (to be posted)

References:

[1] Olsson, A.K., and Austrell, P-E., (2001), "A fitting procedure for viscoelastic-elastoplastic material models," Proceedings of the Second European Conference on Constitutive Models for Rubber, Germany, 2001.
[2] Ottosen, N.S., and Ristinmaa, M., (1999). "The mechanics of constitutive modelling, (Numerical and thermodynamical topics)," Lund University,Division of Solid Mechanics, Sweden, 1999.

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