Takeda Hysteretic Spring > Stiffness Parameters
The Takeda hysteretic spring model allows definition of a nonlinear hysteretic relationship between the bending moment My or Mz and the rotation Ry, Rz respectively.
The stiffness in the remaining degrees of freedom is always linear elastic. The My, Mz stiffness can also be defined to behave as completely elastic. For more details on understanding the degrading hysteretic loop one can refer to article "Reinforced Concrete Response to Simulated Earthquakes" by Takeda, Sozen and Nielson (1). This model in the bending direction is more appropriate for reinforced concrete cyclic loading conditions than metals. The model is defined by a penta-linear skeleton curve with bending points for cracking and yielding, both in positive and negative directions and an unloading stiffness degradation coefficient alpha.
Takeda Hysteretic element is used for dynamic time history analysis when Non-linear spring option is selected under Recalc pad. Takeda element has linear stiffness in static/eigen calculation and nonlinear properties used only in time history calculation. This element does not consider any p-delta effects occurring due to axial load and translation of spring element.
| Setting | Description |
|---|---|
| From/To/Step | Element series, for which the section properties are input/modified. |
| Element type | Takeda Hysteretic Spring: Type TakHyst |
| Linear Stiffness Kx, Ky ,Kz, Rx, Ry, and Rz | Linear stiffness in translation and rotation local x, y & z directions of the spring element. This stiffness is only used in linear and Eigen analysis. The local x direction is always considered perpendicular to the plane of the Takeda element. |
| Nonlinear Stiffness Ry, and Rz | The Penta linear dynamic stiffness may only be defined for bending Ry and Rz directions. This is done by defining a moment rotation curve which can be input in the list box directly. The local x direction is always considered perpendicular to the plane of the element. |
| Alpha | Unloading stiffness degradation parameter (between 0.0 and 0.6) |
| Hyst. Rule |
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