GIRAFFE: Generic Interface Readily Accessible for Finite Elements

Table of contents

• Introduction
• Building and compiling
• Executing
• Documentation
• Dependencies
• Disclaimer

Introduction

Giraffe is the acronym of “Generic Interface Readily Accessible for Finite Elements”. It is a platform coded in C++, with the objective of generating a base interface to be used by researchers, to implement their finite element formulations. It was already employed for modeling structural problems, with beam, shell, and rigid body elements. It also has discrete element method capabilities, particularly handling polyhedral elements. Giraffe has resources to switch on/off boundary conditions, loads, joints, contacts, etc. straightforwardly. This leads to creating scenarios where load sequence is an issue. Furthermore, it provides numerical strategies to achieve solutions to challenging nonlinear problems. Also, post-processing possibilities are convenient, with an organized set of post files, which is automatically generated for using Paraview. Giraffe has a proper input file format, documented in its user's manual.

The platform is coded in a way that permits embracing new elements, novel contact formulations, and proposition of constraint equations, among other features. With that aim, the Giraffe code was started in 2014 by Prof. Alfredo Gay Neto, at the University of Sao Paulo, Brazil.

Giraffe was started as a generalization of a previous-developed finite element code, named “FemCable”, which had the objective of simulating offshore structures: risers for oil exploitation. It had implementations of geometric nonlinear beam elements and classical node-to-surface contact formulation. Since a natural expansion required including new contact models, new structural elements, and other resources, Giraffe was designed from scratch to have all the models included in “FemCable” and to embrace easy inclusion of new resources, using object orientation programming. Giraffe is under continuous development by Prof. Alfredo Gay Neto, co-workers, and supervised students.

Building and compiling

You can build the Giraffe project and compile it automatically with the auxiliary batch files here provided. The provided batch files automatically download prerequisites from public repositories. For that, you need to install Git. The following instructions can be followed to install Giraffe in MS Windows OS:

1. Install the following software:

   Git

   CMake

   Intel oneMKL

   Microsoft Visual Studio

   2. Clone GIRAFFE repository. For that, you can use the git command or download it manually using the web browser.

      git clone https://github.com/alfredogneto/GIRAFFE.git

   3. Run the provided install_dependencies.bat.

   install_dependencies.bat: creates a /dependencies folder, clones exprtk, Eigen and vcpkg, such as installs the last one. Afer, it installs arpack-ng. It creates environment variables for GIRAFFE execution. All variables are created in the user's profile and are based in the folder where Giraffe is located on your computer.

   4. After install_dependencies.bat finishes, manually add the following entries to the user environment variable Path: %GIRAFFE_PATH% and %MKL_PATH%. This can be done, for example, using the procedure described here. PS: If you want to add these paths to the system version of Path, you have to copy the variables into the system scope too.

   5. The last step is to run build.bat.

   build.bat: sets up the project files for Microsoft Visual Studio and builds Giraffe (Release mode by default). Both the project files and executable can be found in ./build and ./build/Release respectively.

Executing

Giraffe execution is based on reading input files, with a proper syntax. Examples of input files are found in the folder /inputs.

To execute Giraffe, you simply have to open its executable file either in Microsoft Visual Studio environment or directly in the folder created after compiling it (/build/Debug) or (/build/Release), depending on the option chosen (default is Release). The only instruction Giraffe needs is the name of the input file.

The Giraffe input file must be located inside a folder with the same name as the input file. It is mandatory to use the file extension *.inp for the input file. Files with different extensions or with no extensions will result in error messages when Giraffe tries to read them. Example: the input file named tutorial01.inp is located inside a folder named tutorial01.

The folder with the input file can be located:

1. In the directory of Giraffe.exe executable file;
2. In the folder /inputs located in the installation directory of Giraffe software;
3. In the public /Documents/Giraffe/ folder.

When trying to read an input file, Giraffe seeks it in the sequence here presented. If not succeed, an error message is prompted to the user.

Documentation

A folder /documentation is provided, containing Giraffe user's manual and tutorials.

Dependencies

To compile and execute Giraffe you need some additional resources:

• Intel oneMKL, as part of the Intel oneAPI. You need to install this library, which will be linked to Giraffe via CMake;
• exprtk, as a library used for mathematical expressions interpretation in Giraffe input files;
• Eigen, as a library used for mathematical operations, matrix organizations, etc.;
• arpack-ng, as a library used to evaluate large-scale eigenvalue problems.

Disclaimer

Currently, Giraffe is built and tested only with Microsoft Visual Studio and the MS Windows OS. We plan to expand it to Linux and Mac soon.