Upheaval Buckling Tools

class pysubsea.upheaval_buckling_tools.PropType(*, bending_stiffness=0.0, submerged_weight=0.0, propped_shape_height=0.0, effective_length_factor=1.0, euler_buckling_mode=1)

Bases: object

Class for calculating the properties of natural prop-type imperfections.

Parameters:

• bending_stiffness (float or array-like, optional) – Bending stiffness for the condition of interest.

• submerged_weight (float or array-like, optional) – Submerged weight for the condition of interest.

• propped_shape_height (float or array-like, optional) – Imperfection height for the condition of interest.

• effective_length_factor (float or array-like, optional) – Effective length factor for the condition of interest. Default is 1.0 (pinned-pinned); common values are pinned-pinned=1.0, fixed-pinned=0.699, fixed-fixed=0.5, and fixed-free=2.0.

• euler_buckling_mode (int, optional) – Euler buckling mode for the condition of interest. Default is 1 (first mode).

propped_type_length()

Compute natural prop-type imperfection length.

Returns:

length – Natural prop-type imperfection length.

Return type:

np.ndarray

Examples

>>> prop = PropType(
...     bending_stiffness=[18272109.437121, 37864772.21769765],
...     submerged_weight=[695.39794758, 1029.76124826],
...     propped_shape_height=[0.5, 0.5]
... )
>>> prop.propped_type_length()
array([62.372..., 67.839...])

propped_shape_buckling_force()

Compute propped shape buckling force.

The equation used is:

P = 4 * (EI * Ws / h)^(1/2)

where:

• P is the propped-shape buckling force,

• EI is the bending stiffness,

• Ws is the submerged weight, and

• h is the propped-shape imperfection height.

Returns:

propped_shape_buckling_force – Propped shape lateral buckling force.

Return type:

np.ndarray

Examples

>>> prop = PropType(
...     bending_stiffness=[18272109.437121, 37864772.21769765],
...     submerged_weight=[695.39794758, 1029.76124826],
...     propped_shape_height=[0.5, 0.5]
... )
>>> prop.propped_shape_buckling_force()
array([ 637655.3903..., 1117019.9655...])

euler_buckling_force()

Compute Euler buckling force.

The equation used is:

Pcr = n^2 * pi^2 * EI / (K * L)^2

Returns:

euler_buckling_force – Euler critical buckling force, Pcr.

Return type:

np.ndarray

Examples

>>> prop = PropType(
...     bending_stiffness=[18272109.4, 18272109.4, 37864772.2, 37864772.2],
...     submerged_weight=[695.4, 695.4, 1029.8, 1029.8],
...     propped_shape_height=[0.5, 0.5, 0.5, 0.5],
...     effective_length_factor=[1.0, 1.0, 1.0, 1.0],
...     euler_buckling_mode=[1, 2, 1, 2]
... )
>>> prop.euler_buckling_force()
array([ 46355.3847..., 185421.5390..., 81204.9721..., 324819.8885...])