DDFOR 1.0: Simple direct stiffness method solver (for statics of frames). This program is written in the K&R syntax of the C programming language. It is meant for retrocomputing (computers from 80'). Licensed under the GNU GPL version 2. MANUAL ====== Introduction ------------ The code can solve beams and frames in x-y plane. Only static loads (forces in nodes, moments in nodes, continuous loads on beams are allowed). The code uses the Direct Stiffness Method (http://en.wikipedia.org/wiki/Direct_stiffness_method) Usage ----- ddfor [inputfile [outputfile] [elementforcesfile] [plotfile] [mode]] If no "inputfile" is given then program pseudo-interactively asks for data (note: there is no command line editing and no undo). The pseudo-interactive feature may not work in no-POSIX environments (in DOS). If no "outputfile" is defined then results will by written to the terminal. Detailed list of internal forces is only available if the "elementforcesfile" file name is provided. The "plotfile" can be used to save data in Gnuplot-compatible form. The 2nd and 3rd columns cover X and Y coordinates, the 4th and 5th are for N, the 6th and 7th are for V and the 8th and 9th are for M internal forces. If name of any of the output files starts with the "0" or the "-" characters the this file is not written. The "mode" have to be: - non-present of 0 for statics - 1 for stability - 2 or mode for modal analysis (the number >2 means number of frequencies to be computed). Note: there is a bug for higher modal frequencies - do not use them! Conventions ----------- X-Y axes orientation: ^ Y | o---> X Positive forces and displacements orientation: ^ +FY, +uy | o---> +FX,+ux Positive load on beams: -> -> -> -> -> -> +n (in direction of beam axis ... type 1) vvvvvvvvvvvvvvvvvv +v (normal to beam ... type 2) Element types: -------------- 0 .. |---| .. no hinges 1 .. o---| .. hinge at start 2 .. |---o .. hinge at end 3 .. o---o .. two hinges Boundary conditions types ------------------------- 1 .. displacement in X direction (ux) 2 .. displacement in Y direction (uy) 3 .. rotation Loads (in nodes) types ---------------------- 1 .. force in X direction (Fx) 2 .. force in Y direction (Fy) 3 .. moment Element loads types ------------------- 1 .. continuous load in X direction (n) 2 .. continuous load in Y direction (v) Graphical output recomendations ------------------------------- The Gnuplot software can be used for visualiztion of results ( http://www.gnuplot.info ). The output is comatible with the Gnuplot 3.2 and better. The command syntax is: Geometry of structure: plot "plotfile" using 2:4 with linespoints Normal forces: plot "plotfile" using 2:4 with lines,"plotfile" using 2:5 Shear forces: plot "plotfile" using 2:4 with lines,"plotfile" using 2:7 Bending moments: plot "plotfile" using 2:4 with lines,"plotfile" using 2:9 Compatibility (tested) ---------------------- GNU/Linux (Ubuntu/x86) GNU/Linux (Debian/armhf) GNU/Linux (Debian/arm) GNU/Linux (OpenWRT/mipsel) 2.11BSD (PDP-11) IRIX 6.5 (SGI MIPS) IRIX 5.3 (SGI MIPS) Mac OS 10.3 (PowerPC) MS-DOS 2.x (Atari Portfolio) MS-DOS 3.x (HP 95LX, Psion MC600) MS-DOS 5.x (HP 200LX)