SelfCentering Material: Difference between revisions

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| style="background:yellow; color:black; width:800px" | '''uniaxialMaterial SelfCentering $matTag $k1 $k2 $sigAct $beta <$epsSlip> <$epsBear> <rBear>'''
{|
|style="background:yellow; color:black; width:800px" | '''uniaxialMaterial SelfCentering $matTag $k1 $k2 $sigAct $beta <$epsSlip> <$epsBear> <rBear>'''
|}
|}


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NOTES:


*This material is implemented as a compression-only gap material. '''$Fult''' and '''$gap''' should be input as negative values.
* Recomended Values:
{|
|  style="width:80px" | '''$Kmax''' || = 20300 kN/m of abutment width
|-
|  '''$Kcur''' || = $Kmax
|-
| '''$Rf''' || = 0.7
|-
| '''$Fult''' || = -326 kN per meter of abutment width
|-
| '''$gap''' || = -2.54 cm
|}
----
DESCRIPTION:
This file contains the class implementation for HyperbolicGapMaterial. This material is based on abutment stiffness models for bridge simulation proposed by Patrick Wilson and Ahmed Elgamal at UCSD. The abutment stiffness models are based on large-scale abutment tests performed on the outdoor shaking table at UCSD. The model is described for a 1.68 meter (5.5 ft) tall backwall height (typical size) and a 1 meter wide section along the width of the abutment (to be scaled accordingly). The hyperbolic force-displacement model is based on work by Duncan and Mokwa (2001) and Shamsabadi et al. (2007) with calibrated parameters from UCSD abutment tests. This model matches very well with test data up to 7.64 cm of longitudinal displacement.


:<math>F(x) = \frac{x}{\frac{1}{K_\text{max}} + R_f \frac{x}{F_\text{ult}}}</math>
[[Image:SC1.png]]


[[Image:SC2.png]]
[[Image:SC3.png]]


[[Image:HyperbolicGapA.png]]
[[Image:SC4.png]]
[[Image:SC5.png]]


[[Image:HyperbolicGapB.png]]
[[Image:SC6.png]]
[[Image:SC7.png]]


----
----

Latest revision as of 21:48, 23 March 2010



This command is used to construct a uniaxial self-centering (flag-shaped) material object with optional non-recoverable slip behaviour and an optional stiffness increase at high strains (bearing behaviour).

This material is primarily used to model a self-centering energy-dissipative (SCED) brace (Christopoulos et al., 2008) with the option to model the slippage of an external friction fuse (which causes non-recoverable deformation above a given brace strain). In practice, the external friction fuse is used to limit the amount of force in the brace (since the post-activation stiffness is generally non-zero). The bearing option is used to approximately model the effect of bolt bearing in the brace or external fuse mechanisms, which causes a steep increase in the stiffness of the brace. For self-centering energy-dissipative brace design, this bearing effect model may be used to impose a limit on slip or activation strain based on the anticipated available strain capacity of the mechanism. Note that this bearing effect is only intended to be a flag to indicate the existence of bearing; the SCED brace system should be designed such that the brace will not experience such bearing in practice.

This material type could potentially be used for any comparable self-centering system that exhibits a flag-shaped hysteretic response (for example: rocking wall systems if the uniaxial material is used as a moment/rotation hysteresis).


uniaxialMaterial SelfCentering $matTag $k1 $k2 $sigAct $beta <$epsSlip> <$epsBear> <rBear>


$matTag integer tag identifying material
$k1 Initial Stiffness
$k2 Post-Activation Stiffness (0<$k2<$k1)
$sigAct Forward Activation Stress/Force
$beta Ratio of Forward to Reverse Activation Stress/Force
$epsSlip slip Strain/Deformation (if $epsSlip = 0, there will be no slippage)
$epsBear Bearing Strain/Deformation (if $epsBear = 0, there will be no bearing)
$rBear Ratio of Bearing Stiffness to Initial Stiffness $k1



REFERENCES:

Christopoulos, C., Tremblay, R., Kim, H.-J., and Lacerte, M. (2008). "Self-Centering Energy Dissipative Bracing System for the Seismic Resistance of Structures: Development and Validation" Journal of Structural Engineering ASCE, 134(1), 96-107.

Tremblay, R., Lacerte, M., and Christopoulos, C. (2008). "Seismic Response of Multistory Buildings with Self-Centering Energy Dissipative Steel Braces" Journal of Structural Engineering ASCE, 134(1), 108-120.



Code Developed by: Jeff Erochko, University of Toronto

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