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OpenSees in NextFEM Designer |
setup and resources |
OpenSees is not included with NextFEM Designer. To be able to perform analyses within NextFEM Designer with OpenSees, set it as the default solver from the Tools / Options / Solvers form. By downloading the OpenSees software from the official website, the user accepts its license under his own responsibility. By copying OpenSees.exe into the NextFEM Designer installation folder, the solver path option is filled in automatically.
Fiber sections
NextFEM Designer supports fiber model writing for steel and reinforced concrete frame structures. You can also specify the quality of the mesh to be imposed on the section. This feature is free, available to all users and can also be used for professional purposes.
IMPORTANT: To use modal and response spectrum analyses and plastic hinges, ActiveTcl 8.6 must be installed and added to path. If can use a simple OpenSees.exe once you installed Tcl libraries.
Loads handling
NextFEM Designer is able to convert any kind of load into OpenSees-supported loading. For instance, you can use in your model distributed moments along beams, edge and surface loads for planar elements and even volume loads; Designer will always produce a compatible sets of sp/eleLoad/load in the OpenSees model.
For thermal distorsion loads, NextFEM Designer can tranform the load into forces to be applied to 3D beam and shell elements, for displacement and stress consistency.
Results handling
Results read from recorders can be imported automatically by specifying the kind of data.
Obviously, when analysis is directly handled by NextFEM Designer, results are imported automatically.
In addition, NextFEM Designer carries-out further operations in post-processing results:
– for beam elements, results are avaialble only at the ends of the element; NextFEM Designer can shown a continuous diagrams for internal forces by using the command “Results / More output stations”
– for shell and solid elements, stress/force recovery at nodes is performed automatically, hence you can read stresses and forces directly at nodes instead of reading Gauss points.
Exporting TCL model
By command “Export“, the TCL model can be exported for free, since this is covered by the basic version of NextFEM Designer. In this way you can obtain automatically fiber sections, loads conditions and analysis sequence (e.g. static performed before a dynamic analysis). The provided TCL output is commented to improve its readability.
To convert it to OpenSeesPy, please use toOpenSeesPy.py in the official OpenSees repo.
Advanced usage
A collection of OpenSees procedures is shipped with NextFEM Designer, in the file named “procedureXXX.tcl” in the installation folder. NextFEM provides for free use some procedures and the Response Spectrum and UmfPack2 libraries, made available to the public as described below.
See the manual for pre- and post-processing
See the manual for Response Spectrum analysis library
Response Spectrum analysis for OpenSees
To perform a Response Spectrum analysis based on modal results, use the following command:
dynModal $numModes $spectrum $patternID $comb $csi $dir1 $dir2 $dir3
where $numModes is the number of modes the user wants to combine, $spectrum is the name of the file containing the spectrum points, $patternID is the ID to be given to the load patterns created internally to perform the required linear static analyses, $comb let the user choose whether the SRSS or CQC method should be used, $csi is the damping ratio which is used to calculate the correlation coefficients needed when performing CQC.
The last three parameters ($dir1, $dir2, $dir3), which may assume a value of 0 or 1, are needed to specify the directions associated with the spectrum.
You need to install ActiveTCL 8.6 before to use it.
64 bit – updated 8th Feb 2022 – OpenSees 3.2.1 and above
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NOTE: you can find an updated version of Response Spectrum library inside the NextFEM Designer 64bit installation.
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Download the example from here: frame_ex
[docxpresso file=”http://www.nextfem.it/it/wp-content/testi/RSAmanual.odt” comments=”true”]