About STKO

The Scientific ToolKit for OpenSees, aka STKO, is an advanced Graphical User Interface (GUI) for OpenSees. STKO gives companies, scientists, researchers, academics, and individuals the ability to harness the full power of OpenSees. It is the only pre and postprocessor that includes ALL materials, elements, conditions, and interactions offered in OpenSees, allowing you to take advantage of all the potential that OpenSees has to offer.
As you create your model using STKO’s graphic interface, the software creates an input (Tool Command Language, TCL) and output file with the information contained in your model. Once you have built the model, you can create and run the analysis of your choice. The software will build an HDF5-based output database with the analysis results, which can be opened and processed in the postprocessor. The Python scripting interface means that the already powerful pre and postprocessors can be customized and programmed as needed.

Why choose STKO?

It’s Powerful

STKO manages multiprocessors for the analyses using OpenSees SP and MP and generates the output files using parallelization technologies with the HDF5 database. STKO empowers the user to create models with millions of degrees of freedom using a large number of processors.

It’s Creative


This is no basic GUI. STKO creates sophisticated and complex models, and it renders your data in an aesthetically pleasing manner and in a way that makes the information more tangible and accessible.


Our software engineers closely follow developments in OpenSees and collaborate with an OpenSees compiler to ensure that STKO capabilities are supported in OpenSees and vice versa. Our research and engineering teams collaborate to implement the latest materials, theories, and models in STKO.


With OpenSees, the different recorders produce different output files that only contain data. To make the output easier to use, we created a new MPCO recorder, an hdf5 database. It efficiently manages large amounts of input and output data and records everything you request in a single well-structured file, saving not only the results but also the model characteristics.


The Python API allows users to customize their experience. In the pre-processor, users can manipulate the model input with the Python scripting interface to create personalized modeling tools, parametric analyses, artificial intelligence codes, and much more. In the postprocessor, it can be used to directly interact with the database to create customized engineering demand parameters, plots, and a lot of different output data.


It is a common misconception that the program was developed only for uniaxial materials and 1D elements, and many different kinds of models and analyses can be run in STKO. OpenSees is a very powerful tool and combined with STKO, it can solve complex 3D solid problems even in the fields of mechanical and aeronautical engineering.


STKO is interoperable with several other major 3D modeling programs. It will be a sinch to incorporate it into your workflow and reap the benefits of this powerful, creative, sophisticated, state-of-the-art, efficient, customizable, universal, and advanced software.

It’s Collaborative

With the Open-Source External Solver Library in STKO now available to the public on GitHub, users can collaborate directly with our team to program new automations and link new OpenSees components to STKO. Users can also use GitHub to report bugs or issues and suggest new features.