pyconmech 0.6.0

Input model

There are two ways to specify and input a structural model (geometry, material, cross sections, joint releases, support conditions, and loads) to conmech:

1. directly input data following class structures specified in pyconmech.frame_analysis.io_base

2. write your data in a JSON format and input the file path to conmech (See file examples here.

The easiest way to generate the model JSON file by exporting from a Karamba3D model in Rhino-Grasshopper. A example GH export file is provided:

You can also parse your model JSON file back to Rhino/GH for visualization/debugging by using the parse GH example file.

Analysis

After you have the input model ready, analysis is straight-forward:

from pyconmech import StiffnessChecker

sc = StiffnessChecker.from_json(json_file_path=frame_file_path, checker_engine="numpy", verbose=True)
gravity_load = GravityLoad([0,0,-1])
sc.set_loads(gravity_load=gravity_load)

# if the structure's nodal deformation exceeds 1e-3 meter,
# we want the checker to return `sol_success = False`
trans_tol = 1e-3
sc.set_nodal_displacement_tol(trans_tol=trans_tol)

# existing elements' indices
existing_ids = [0,4,88,6]

# False if the analysis result
sol_success = sc.solve(existing_ids)

# Get all the analysis information:
# nodal deformation, fixity reactions, element reactions
success, nD, fR, eR = sc.get_solved_results()

See python unit tests for more examples.

Build python bindings

Prerequisites

The following dependencies come from pybind11 for building the python wrappers.

On Unix (Linux, OS X)

• A compiler with C++11 support

• CMake >= 3.1

On Windows

• Visual Studio 2015 (required for all Python versions, see notes below)

• CMake >= 3.1

Then, clone this repository and pip install.

cd conmech
python -m pip install .
# or python3 if default python is 2.x (OSX or Linux)
# try the following flags when updating: --user --upgrade --force

With the setup.py file included in the base folder, the pip install command will invoke CMake and build the pybind11 module as specified in CMakeLists.txt.

Note:

conmech’s python bindings are built with a CMake-based build system via pybind11. Take a look at cmake_example for pybind11 if you want to learn more about this.

conmech depends on Eigen for linear algebra and nlohmann::json for json (de-)serialization, both of which are handled automatically by cmake for downloading.

Build C++ code

mkdir build
cd build
cmake ..
make -j2 # Unix

Or on Windows, replace the last line with

cmake --build .

Credits

Yijiang Huang. Conmech. https://pypi.org/project/pyconmech/. 2020.

This package was initiated and maintained by Yijiang Huang @yijiangh and other contributors.

References

The following textbook is an excellent resource for learning 2D/3D truss/frame analysis, many of conmech’s unit tests are using examples in this textbook as analytical benchmarks:

McGuire, W., R. H. Gallagher, and R. D. Ziemian. “Structural Analysis, Title: Matrix Structural Analysis.” (2015).

Related repos

Frame3dd: A static and dynamic structural analysis software of 2D and 3D frames and trusses with elastic and geometric stiffness written in C.