Frame3DD. Static and Dynamic Structural Analysis of 2D and 3D Frames.
Department of Civil and Environmental Engineering
Edmund T. Pratt School of Engineering
Duke University - Box 90287, Durham, NC 27708-0287
Henri P. Gavin, Ph.D., P.E., - Associate Professor -


Frame3DD is free open-source software for static and dynamic structural analysis of 2D and 3D frames and trusses with elastic and geometric stiffness. It computes the static deflections, reactions, internal element forces, natural frequencies, mode shapes and modal participation factors of two- and three- dimensional elastic structures using direct stiffness and mass assembly. Frame3DD has its own text-file input format (.3dd), but additionally supports matlab (.m) and spreadsheet (.csv) file formats, and offers graphical output including mode shape animation via Gnuplot version 4.6.

The program is written in plain ANSI C. The source code includes: frame analysis, LDL' decomposition, LU decomposition, Newton-Raphson iteration, sub-space iteration, Stodola iteration, Sturm eigenvalue check, static condensation, Guyan reduction, and dynamic condensation.

Included in the program is a parser for Microstran .ARC files. Currently, we are able to load and view exported Microstran models, and we plan to incorporate ".ARC" as an alternative input format.

Frame3DD is licensed under the GNU General Public License and is maintained at source-forge.

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The following input data files are included with the Frame3DD download packages. Click below to see formatted and commented input data, the associated output data, as well as plot and movie outputs generated using the program.

Example Input Data (.txt)Output Data (.txt)Input Data (.csv)Output Data (.csv)PlotMovie
(A) 2-D Pratt Truss exA.3ddexA.out exA.csvexA_out.CSV Plot
(B) Pyramid Frame exB.3ddexB.out exB.csvexB_out.CSV Plot
(C) Tetrahedral Frame exC.3ddexC.out exC.csvexC_out.csv Plot
(D) Un-Restrained Frame exD.3ddexD.out exD.csvexD_out.CSV Plot
(E) Lateral-Torsional Coupling exE.3ddexE.out exE.csvexE_out.CSV Plot
(F) Building with Seismic Isolation exF.3ddexF.out exF.csvexF_out.CSV Plot
(G) Building with Set-Back exG.3ddexG.out exG.csvexG_out.CSV Plot
(H) Pedestrian Ramp Lateral Sway exH.3ddexH.out exH.csvexH_out.CSV Plot
(I) Triangular Tower exI.3ddexI.out exI.csvexI_out.CSV Plot
(J) Tesseract exJ.3ddexJ.out exJ.csvexJ_out.CSV Plot

Microstran Viewer

As a first step to implementing basic interoperability between Frame3DD and other structural analysis programs, we have implemented a parser and viewer that reads Microstran ".ARC" files and displays them in 3D. This has already proven to be a useful tool, even without structural analysis capabilities. We propose next to implement support for converting between Frame3DD input files and Microstran .ARC files. This will allow Frame3DD results to be visualised using OpenGL graphics, as well as allowing us to validate Frame3DD in comparison with commercial tools that support this file format.

Related Links


Frame3DD is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License (GPL) as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

Simply put, the GPL says that anyone who redistributes the software, with or without changes, must pass along the freedom to further copy and change it. By distributing the complete source code for Frame3DD under the terms of the GPL, we guarantee that you and all other users will have the freedom to redistribute and change Frame3DD.

Frame3DD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License (GPL) and the GNU General Public License FAQ for more details.

© 1992-2014 Henri P. Gavin. Verbatim copying and distribution is permitted in any medium, provided this notice is preserved.

Department of Civil and Environmental Engineering
Duke University, Box 90287
Durham, NC 27708-0287

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