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LittleDef (fem1) v3

Lightweight 2D Frame Structural Analysis for Unix and Windows.

Overview

LittleDef is a portable, fairly fast, and relatively feature-rich 2D Finite Element Method (FEM) application for frames and beams (1D elements only). Originally designed for SGI IRIX workstations. It specializes in civil engineering statics, offering Eurocode-compliant verification for steel, concrete, timber, and masonry. Please note that the Eurocode part is now for reference only and it is obviously incomplete. Anyway, 2nd generation Eurocode preview desing tools are available, too (albeit they are even more limited that current Eurocode support).`

Note that the LittleDef is just a set of Tcl scripts (over 50 000 lines of code in total) and a bunch of ANSI89 C files.

LittleDef on IRIX with FVWM2, screenshot showing computed bending moments.

Key Features

Analysis Types: Linear Static, P-Delta (2nd order), Large Deformations, Newton-Raphson for elastic-plastic problems. Modal (Frequencies), Seismic (Response Spectrum), and Elastic Stability (Buckling).
Eurocode Design: Integrated modules for EN 1990 (Combinations), EN 1992 (Concrete), EN 1993 (Steel), EN 1995 (Timber), and EN 1996 (Masonry).
High Performance: Sparse matrix assembly and solver, with an optional ANSI89 C accelerator for heavier computations. The plotting of results and orther user-facing fucntionality is of course unaccelerated.
FEPro 3D Extension: Includes the FEPro structured mesher, 3D visualizer, and nonlinear solver for shell and solid elements with OpenGL rendering, plasticity, and 3D STL/DXF export. At the moment, the FEPro is a specialised tool for analzsis of 3D beams created from LittleDef-exported crossections. But general meshes can be imported and support and loads can be applied to them (sit limitations). The FEPro heavily depends on C aceleration library (but can be run as a pure Tcl scrips, at cost of speed)
Portable: Pure Tcl/Tk 8.0+ codebase. Runs on IRIX, Linux, BSD, and Windows The ANSI90 C-compiant accelerator library can be built (tested on the Linux and the IRIX 6.5) and is automaticaly loaded by the Tcl program.
Background Blueprints: Load raster images (PNG, GIF, JPEG) and vector CAD drawings (DXF) with 2-Point Calibration, model grid alignment, sub-pixel rational zoom invariance, and global Ctrl+Shift+B clean redraw. This feture is not perfect but it's fast enoug even on IRIX workstations.
Workflow: Native IRIX Interactive Desktop integration (FTR), CLI mode for headless reporting; export to LaTeX, Markdown, EPS, XFIG, and CSV (plaintext, too!).
SAF support: It is possible to import 2D cuts from Static Analysis Format (SAF) files. It is not ideal (many properties are not imported) and might not work for filesproduced by an exotic software. But hey, the SAF is an XLSX file in nature and you are able to read it into the LittleDef on your IRIX machine! (note: unzip binary in $PATH is required on the platform where you wish to use this feature). The LittleDef can write models into the SAF files, too.

Requirements

LittleDef requires a Tcl/Tk interpreter version 8.0 or newer. You can find more information and downloads at the official Tcl/Tk website.

Windows: We recommend the Magicsplat Tcl/Tk installer.
Linux: Install using your package manager (e.g., sudo apt install tk on Debian/Ubuntu).

Usage

Launch the GUI using wish fem1.tcl
Run a headless analysis: wish fem1.tcl --solve model.df
Run a text-only interface: wish fem1.tcl --cli

Text-only interface

The text-only interface includes only subset of LittleDef features but it can work remotely and over slow lines. The GUI version includes option to save and load command from this interface. Note: this code is not tested enough and might have issues with some types of loads.

Moreover, it can plot graphics on Tektronix-compatible terminals (on the XTerm: xterm -t). White graphical representation is somewhat limited limited it is still helful if no other option is available. It the worst case it is possible to use ASCI text-based graphics (it's more an ASCII art than the actual graphics, though).

===========================================================================
LittleDef Retro CLI Command Reference
===========================================================================
  n x y [i]       Create node at (x,y) or update node i
  nl              List all nodes and supports
  nd i            Delete node i
  ml              List available material library
  sl [mat]        List available section profiles (optional filter mat)
  ee m s          Set default element properties (material m, section s)
  e n1 n2 [[h1] h2] Create/modify element between nodes n1 and n2
  e j n1 n2 ...   Create/modify element j between nodes n1 and n2
  el              List all elements
  q i q1 q2       Set transverse load on element i (start q1, end q2)
  qn i q1 q2      Set axial load on element i (start q1, end q2)
  ql / qnl        List transverse or axial element loads
  qg i / qng i    Delete transverse or axial load on element i
  f i dir val     Set force on node i (dir = X, Y, Z/M)
  fl              List all point forces
  fd i dir        Delete force on node i in direction dir
  d i dir [val]   Set support/prescribed displacement on node i
  dl              List all supports
  dd i dir        Delete support on node i
  lc [name]       Set or create active load case (lc add name / lc name)
  lcl             List defined load cases and load combinations
  comb add c lc1 f1 ... Define load combination c
  sol [type]      Solve (type: linear, buckling, pdelta, plastic, modal)
  gp              Plot model geometry to Tektronix terminal
  ap [mode]       Plot ASCII text art model geometry to plain terminal
  rp              Plot support reactions to Tektronix terminal
  rl [fname]      List reactions (optional save to fname)
  rnl [i] [fname] List normal forces (all or detailed for element i)
  rvl [i] [fname] List shear forces (all or detailed for element i)
  rml [i] [fname] List bending moments (all or detailed for element i)
  rdl [i] [fname] List deformations (all or detailed for element i)
  rnp [i]         Plot normal forces on Tektronix terminal
  rvp [i]         Plot shear forces on Tektronix terminal
  rmp [i]         Plot bending moments on Tektronix terminal
  rdp [i]         Plot deformations on Tektronix terminal
  batch fname     Execute commands from script file fname
  wiz [type]      Wizard generator (wiz truss pratt|howe|warren or wiz frame)
  report [fname]  Print or save full text analysis report
  open fname      Open model file (.df)
  save fname      Save model file (.df)
  history / hi    List command history (!n, !prefix, !! to re-execute)
  help [cmd]      Display general or command-specific help
  quit / exit     Exit program
===========================================================================
Type 'help ' (e.g. 'help n', 'help sol', 'help e') for command details.

Download

Complete Package (Program + Documentation) - recommended
User Guide (HTML)