Introduction

pondpy is a package built to aid in the design of low-slope roof bays for ponding stability and impounded rain loading. It utilizes a series of purpose-built finite element and ponding analysis classes and methods to be as intuitive as possible for the modern engineer.

Installation

Install pondpy with pip:

pip install pondpy

Usage

The PondPyModel class is designed to work with several purpose-built classes that help the user organize their input into a form that are readily utilized to build and analyze the model. These are the PrimaryFraming, SecondaryFraming, and Loading classes. In addition, the package is designed to work with the steelpy and joistpy packages, though any object containing the requiring information attribures (i.e. moment of inertia, cross-sectional area, elastic modulus, etc.) could be used in lieu of either package.

To create and analyze a roof bay model, first import the required dependencies and classes:

from joistpy import sji
from steelpy import aisc

from pondpy.analysis.fem_analysis import (
    SteelBeamSize,
    SteelJoistSize,
)

from pondpy.analysis.pond_analysis import (
    PrimaryMember,
    PrimaryFraming,
    SecondaryMember,
    SecondaryFraming,
    Loading
)

from pondpy.pondpy import PondPyModel

Next, define the steel shapes and joist designations in your model.

w12x16 = SteelBeamSize('W12X16', aisc.W_shapes.W12X16)
w16x26 = SteelBeamSize('W16X26', aisc.W_shapes.W16X26)
k_14k1 = SteelJoistSize('14K1', sji.K_Series.K_14K1)

Next, define the primary and secondary framing in the roof bay framing system. Note that all inputs should be in kips and inches.

p_length = 20*12 # length of primary members in inches
s_length = 20*12 # length of secondary members in inches

# Support types are designated by tuples representing (Tx, Ty, Rz).
# A 0 indicates the degree of freedom is unrestrained while a 1 indicates a 
# restrained degree of freedom.
p_support = [[0, (1, 1, 0)], [p_length, (1, 1, 0)]]
s_support = [[0, (1, 1, 0)], [s_length, (1, 1, 0)]]

p_girder1 = PrimaryMember(p_length, w16x26, p_support)
p_girder2 = PrimaryMember(p_length, w16x26, p_support)
s_beam1 = SecondaryMember(s_length, w12x16, s_support)
s_beam2 = SecondaryMember(s_length, w12x16, s_support)
s_joist1 = SecondaryMember(s_length, k_14k1, s_support)
s_joist2 = SecondaryMember(s_length, k_14k1, s_support)
s_joist3 = SecondaryMember(s_length, k_14k1, s_support)

p_framing = PrimaryFraming([p_girder1, p_girder2])
s_framing = SecondaryFraming([s_beam1, s_joist1, s_joist2, s_joist3, s_beam2])

Note that each member should be individually defined as shown above. Otherwise, the loadings will not be applied correctly to the members.

The roof slope can optionally be set in the SecondaryFraming object by using the keyword slope and entering the roof slope in inches/foot. The default value is 0.25.

Next, define the loading in the roof bay.

p_framing = PrimaryFraming([p_girder1, p_girder2])
s_framing = SecondaryFraming([s_beam1, s_joist1, s_joist2, s_joist3, s_beam2])

q_dl = 20/1000/144 # Surface dead load in ksi
q_rl = 22.4/1000/144 # Surface rain load at secondary drainage inlet in ksi

loading = Loading(q_dl, q_rl)

The input rain load should include the static head and the hydraulic head, but no ponding head.

Finally, define the PondPyModel object and analyze the model.

pondpy_model = PondPyModel(p_framing, s_framing, loading)

pondpy_model.perform_analysis()

Optional arguments for the PondPyModel include:

• mirrored_left: bool indicating whether the roof bay is mirrored on the left side; default is False

• mirrored_right : bool indicating whether the roof bay is mirrored on the right side; default is False

• stop_criterion : float indicating the error in total impounded water weight at which the iterative analysis should be terminated; default is 0.0001

• max_iter : int indicating the maximum number of iterations that should be performed; default is 50

• show_results : bool indicating whether the iteration results should be printed to the terminal upon completion of the analysis; default is True

Analysis Results

Each primary and secondary member is represented within the PondPyModel object by a BeamModel object. As such a great deal of analysis results can be obtained fairly easily once the analysis is complete.

• To access the deflected shape, shear force diagram, or bending moment diagram of a particular member, use the following calls:

  member = pondpy_model.roof_bay_model.secondary_members[0]
  bmd = member.plot_bmd()
  bmd.show()
  

  The shear force diagram and deflected shape can be accessed in a similar fashion using the plot_sfd() and plot_deflected_shape() methods.

  The deflected shape, shear force diagram, and bending moment diagram plots for all members can all be generated by using the RoofBayModel's generate_plots() method.

  plots = pondpy_model.roof_bay_model.generate_plots()
  

  This method returns a dict object with keys bmd, sfd, and defl, each of which is associated with a sub-dictionary with keys Primary and Secondary. Each sub-dictionary contains a list of the associated plot for each primary or secondary member, as applicable.

• The support reactions can be obtained as follows:

  support_nodes = member.support_nodes
  support_reactions = [member.support_reactions[node] for node in support_nodes]
  

Several other attributes of the BeamModel object can be accessed in a similar fashion.

Report Generation

New: A report of the PondPyModel analysis results can now be generated by calling the PondPyModel's generate_report() method.

Once an analysis has been performed, simply call the method:

output_folder = 'path/to/output/folder/'
pondpy_model.generate_report(output_folder)

Once complete, navigate to the folder you designated as the output folder and view the report.

See the example_reports directory in this repo for an example report created using the example in main.py.

Note that only the final analysis results can currently be accessed.

Additional Information

• Documentation
• PyPI Distribution