Tutorial for single file json input¶

This tutorial demonstrates the way of using json file to input the problem definition for Truss Analysis project.

We will use a JSON configuration to define the truss structure and then perform an analysis to determine the reactions and rod forces.

Import Necessary Libraries/Setup¶

To start, we need to import necessary modules and define the project directory and file name prefix.

import pathlib

from npp_2d_truss_analysis import Info, TrussAnalysisProject

pp_project_dir = pathlib.Path('./')
FNAME_PREFIX = 'test'

info = Info(project_directory=str(pp_project_dir.absolute()), file_name=FNAME_PREFIX)

Defining the Truss Structure¶

The truss structure is defined using a JSON string. This includes the definition of nodes, elements, materials, displacements, and forces.

JSON_TEXT="""{
    "mesh":{
        "nodes": [
        {"id": 1, "coordinates": [0, 0]},
        {"id": 2, "coordinates": [0, 2]},
        {"id": 3, "coordinates": [0, 4]},
        {"id": 4, "coordinates": [4, 4]},
        {"id": 5, "coordinates": [4, 2]}
        ],
        "elements": [
        {"id": 1, "connectivity": [4, 3], "materialId": 1},
        {"id": 2, "connectivity": [3, 2], "materialId": 1},
        {"id": 3, "connectivity": [2, 4], "materialId": 1},
        {"id": 4, "connectivity": [4, 5], "materialId": 1},
        {"id": 5, "connectivity": [5, 2], "materialId": 1},
        {"id": 6, "connectivity": [2, 1], "materialId": 1},
        {"id": 7, "connectivity": [1, 5], "materialId": 1}
        ],
        "materials": [
        {"id": 1, "youngModulus": 200000000000.0, "area": 1.0}
        ]
    },
    "displacements":{
        "pin": [
        {"id": 1, "node":4, "angle": 0,"dx": 0, "dy":0}
        ],
        "rollers": [
        {"id": 1, "node": 1, "direction": 1, "angle": -63.4349, "dx":0}
        ]
    },
    "forces": [
    {"id": 1, "node":5, "direction": -180,"x": 40000, "y":0},
    {"id": 2, "node":3, "direction":  200,"x": 20000, "y":0}
    ]
}"""

Creating the Truss Problem¶

We instantiate the truss problem from the JSON text.

truss_problem = TrussAnalysisProject.from_json(json_text=JSON_TEXT,

Updating Forces (optional)¶

Before solving the problem, we update the forces as needed.

truss_problem._forces.update_force_by_id(force_id=1, angle=180+20)

Listing Forces (Optional)¶

Optionally, list the forces to verify the updates.

truss_problem._forces.list_forces()

Solving the Problem¶

Now, we write the input data and solve the truss problem.

truss_problem.write_input_data()
# truss_problem.update_matrices() # optional because solve automatically does that
truss_problem.solve()

Reporting the Solution¶

Finally, we print the solution, including the reactions and rod forces.

print("-------------solution ----------------")
truss_problem.report_reactions(fmt='>12.1f')
truss_problem.report_rod_forces(fmt='>12.1f')

Plotting the truss¶

It is also possible to plot the truss using the following code:

truss_problem.plot_truss(save=True, show=True)

using the flags save and show to save the plot to a file and/or show the plot on the screen.

Plotting truss deformation and stresses¶

After solving the problem, we can plot the deformed state and the stresses.

truss_problem.plot_deformation(save=True, show=True)
truss_problem.plot_stresses(save=True, show=True)