Isolator2SpringSection

Isolator2SpringSection(user_name: str = 'Unnamed', *, tol: float, k1: float, Fy: float, k2: float, kv: float, hb: float, Pe: float, Po: float)

Bases: Section

Horizontal isolator section modeled by two springs in series.

This section type represents a specialized model for seismic isolation bearings. It consists of two springs (one elastic, one elastic-plastic) acting in series, and it accounts for the coupling between horizontal and vertical loads, including the reduction in horizontal stiffness due to axial buckling.

Tcl form

section Isolator2spring <tag> <tol> <k1> <Fy> <k2> <kv> <hb> <Pe> <Po>

Note

k1, Fy, and k2 define the bilinear horizontal response.
kv is the vertical stiffness of the bearing.
hb is the total height of the elastomeric or friction bearing.
Pe is the Euler buckling load, and Po is the static axial load used to compute the initial P-Delta effect.
The algorithm iterates to find the horizontal force that balances the spring series; tol is the convergence tolerance.

Tip

Use this section when modeling lead-rubber bearings (LRB) or high- damping rubber bearings where P-Delta effects and buckling are significant concerns.

Example

from femora.core.model import Model
import femora.components.section.special  # noqa: F401

model = Model()
sec = model.section.special.isolator2spring(
    user_name="Isolator_Unit1",
    tol=1e-6,
    k1=10.0,
    Fy=1.0,
    k2=1.5,
    kv=1000.0,
    hb=12.0,
    Pe=500.0,
    Po=50.0,
)
print(sec.tag)

Create an Isolator2SpringSection with validated parameters.

Parameters:

Name	Type	Description	Default
`user_name`	`str`	User-specified name for the section.	`'Unnamed'`
`tol`	`float`	Tolerance.	required
`k1`	`float`	Initial horizontal stiffness.	required
`Fy`	`float`	Yield force.	required
`k2`	`float`	Post-yield horizontal stiffness.	required
`kv`	`float`	Vertical stiffness.	required
`hb`	`float`	Bearing height.	required
`Pe`	`float`	Buckling load.	required
`Po`	`float`	Axial load.	required

Raises:

Type	Description
`ValueError`	If parameters are not numeric, if dimensions/stiffnesses are non-positive, or if loads are negative.