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figo figo figo

Questions about the interaction between OpenFresco and OpenSees

Hi! I did some study about OpenFresco and OpenSees recently. I computed some examples,and had some questions.

1. What’t the OpenFresco‘s founction? was it just a frame to transfer data? Could OpenFresco do calculating ,such as calculus of interpolation?

2 How did OpenFresco and OpenSees work together?

Thanks very much!

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    Stephen Alan Mahin

    Thanks for your interest in OpenFresco.

    OpenFresco plays an important role in doing hybrid simulations and collaborative computing. It is not intended to do analysis, but rather is what is known as middleware, and provides an interface to allow various programs to seamlessly communicate with one another. The intent is for the user (you) to be able to use what ever analysis tool you want, for example, Matlab, Simulink, Abacus, LS-Dyna, Ansys, or another program you have or write. The main criteria for software to use OpenFresco to do a hybrid simulation is that it permit the development of user defined elements, it has an integration method that can do hybrid simulation, and it permits digital communications with the outside world.

    The other end of the communication mediated by OpenFresco can be multiple local and/or geographically distributed network connected controllers and data acquisitions, or even other computer programs. The basic concept is that some parts of the analysis are done on one computer, some are done by moving specimens in a lab, and other parts are done by other computer programs.

    OpenFresco provides a software framework for you to develop new hybrid/collaborative computing methods, or to do this using what resources you already have. Thus, you can change from one computer program to another, or buy a new controller, or do a test in another lab, without having to do major efforts to reprogram everything.

    OpenFresco is open source, so you can get it and modify it as you like. If you come up with something new and cool, you should submit it so it can be added to the core capabilities so others can use it to. This is the benefit of open source development. The more people use and improve OpenFresco, the better it becomes.

    OpenFresco is also object oriented, which simply means it is highly structured so changes needed to add a new controller, or computer software package or to do a new test set up are easy to do. Thus, at a software level, it needs to know how to communicate with your computer, what to expect from your software, transmit that information to the appropriate place on the internet, make various coordinate transformations to go from the computer analysis software coordinate system to the coordinate system that will be understood by the laboratory controller (or other software package). This is all done in an industry standard secure manner.

    OpenFresco extends the class structure used in OpenSees. Thus, for those interested in using OpenSees, OpenFresco can be dynamically linked during compilation which streamlines the communications a bit. OpenSees is not needed, but it includes a large number of special integration operators that have been developed specifically for hybrid simulation, and it easily permits the addition of new integration methods or other ideas you may have (try that with Abacus).

    You mention various ways of doing calculation of dynamic response. In addition to developing new (or using advanced) integration operators, various hybrid analysis strategies use methods to predict better what the answer should be for the step using information gathered within a step, or permit a guess to be made at the beginning of a step that is corrected during the step. Such predictor-corrector method calculations are generally carried out in real time by a second xPCtarget computer. OpenFresco knows how to communicate with these as well, so if you are interested in numerical methods, you can try many things without needing to write everything from scratch.

    For more information on OpenFresco, see:

    There is a Matlab program called OpenSees Navigator that is a GUI for carrying out OpenSees and OpenFresco analyses without having to learn the details of Tcl programing.

    We are very excited about a new software package that is built on OpenFresco that will carry out simple hybrid tests of small structures. This is a quick start for those interested in hybrid simulation, and might be adequate for 60% of the typical applications.

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