SelfCentering Material

• Command_Manual
  • Tcl Commands
  • Modeling_Commands
    • model
    • uniaxialMaterial
    • ndMaterial
    • frictionModel
    • section
    • geometricTransf
    • element
    • node
    • sp commands
      • fix
      • fixX
      • fixY
      • fixZ
    • mp commands
      • equalDOF
      • rigidDiaphragm
      • rigidLink
    • timeSeries
    • pattern
    • mass
    • block commands
      • block2D
      • block3D
    • region
    • rayleigh
  • Analysis Commands
    • constraints Command
    • numberer Command
    • system Command
    • test Command
    • algorithm Command
    • integrator Command
    • analysis Command
    • eigen Command
    • analyze Command
  • Output Commands
    • recorder
    • record
    • print
    • printA
    • logFile
    • RealTime_Output_Commands
  • Misc Commands
    • eleResponse Command
    • getTime Command
    • getEleTags Command
    • getNodeTags
    • loadConst Command
    • nodeCoord Command
    • nodeDisp Command
    • nodeVel Command
    • nodeAccel Command
    • nodeEigenvector Command
    • nodeBounds
    • print Command
    • remove Command
    • reset Command
    • testIter
    • testNorms
    • wipe Command
    • exit Command
  • DataBase Commands
    • Template:DataBaseCommandsMenu

---

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