GGU-ELASTIC: Short description
As, from personal experience, the reading of manuals is a chore, there will now follow a short description of the main program functions. After studying this section you will be in a position to analyse a strain state using the finite-element-method. You can take program details from the further chapters.
As well as the short description, the last chapter of this manual contains a concrete example, with which program use is thoroughly described.
Design the system that you wish to analyse.
Start the GGU-ELASTIC program and select the menu item "File/New". Select the type of system.
If necessary, fit the page coordinates to those of your system. For this, use the menu item "Page size + margins/Manual resize (editor)".
Then select the menu item "FEM mesh/Define nodes".
Click on the decisive nodes (points) of your system with the mouse. The points will be numbered. Alternatively, you can enter the system nodes in tabular form, using the menu item "FEM mesh/Change (nodes)" or import them via the Windows clipboard e.g. from an Excel table.
If the nodes lie outside of the page coordinates, select the menu item "Page size + margins/Auto-resize".
Then select the menu item "FEM mesh/Manual mesh" and combine the nodes, in groups of three, to triangular elements. In this way you create a rough structure for your system. Alternatively, you can have the program do this automatically, using the menu item "FEM mesh/Automatic".
If you would like to edit the positions of mesh nodes, select the menu item "FEM mesh/Change (nodes)", "FEM mesh/Move (nodes)" or "FEM mesh/Edit (nodes)".
If you would like to analyse a simple rectangular system, you can complete mesh generation in a few seconds using the menu item "FEM mesh/Array".
If you would like to delete a triangular element, select the menu item "FEM mesh/Manual mesh" again and click on the three corner nodes of the appropriate element. Using this menu item , try double-clicking in a triangular element.
If you would like to assign different material properties to different triangles, use the menu item "Boundary/Individual materials" or "Boundary/(Materials) In section" to enter varying material numbers for individual or multiple elements. In the menu item "System/Material properties" an input line appears for each material number.
You can refresh the screen at any time, using the [Esc] or [F2] keys.
You can create a finer structure for your system by selecting the menu items "FEM mesh/Refine individually", "FEM mesh/(Refine) Section" or "FEM mesh/(Refine) All".
Even after refining your FEM mesh you can edit the system as you wish by using "FEM mesh/Define nodes", "FEM mesh/Manual mesh", etc.
In order to get a numerically favourable FEM mesh, you should always select the menu item "FEM mesh/Optimise" and then select the button "Diagonals".
For demonstration purposes you can create acute angled, and thus numerically unfavourable, triangular elements with the menu item "FEM mesh/Move (nodes)". Then select the menu item "FEM mesh/Optimise" ("Topology" button) and follow the effects on the screen.
Define the decisive displacement boundary conditions for your system using, e.g., the menu item "Boundary/Individual displacement BC" or "Boundary/(Displacement BC) In section".
Define the decisive force boundary conditions for your system using, e.g., the menu items "Boundary/Point loads" or "Boundary/Line loads".
If necessary, edit the material properties using the menu item "System/Material properties".
If beam elements (e.g. piles or anchors) are present in the system, define the position of these elements via the menu item "Boundary/Beams", by defining a section along the desired nodes. After pressing the [Return] key you can assign the thus defined beams a material number. The beam stiffness' (EJ and EF) can be edited using "System/Material (beams)".
Simple control of the defined boundary conditions is possible using the menu item "Boundary/Check".
When you have finished FEM mesh generation, select the menu item "System/Analyse", and start the analysis. Before analysis begins a bandwidth optimisation will be carried out, if necessary, in order to achieve a numerically favourably configured equation system.
After completion of analysis you can, if wished, print the results as an output table or save them as a file. In general though, this type of result presentation is less than satisfactory.
Instead, go immediately to the "Evaluation" menu. Here you have a variety of evaluation possibilities. The menu item "Evaluation/Coloured contours" is especially impressive, or the menu item "Evaluation/3D array contours". The dialog boxes which then appear can almost always be left using "OK", without further changes having to be made. The program will usually suggest sensible input. The "Determine extreme values …" button should be clicked once however, otherwise an error message will appear, with correction suggestions.
If the connected printer is a colour printer and is correctly installed in WINDOWS, you can create colour output by selecting the menu item "File/Print and export" and then selecting the "Printer" button in the dialog box which appears. For black and white printers, grey scales will be used.
At the end of the manual, program use is described in detail using a concrete example.
When carrying out analyses, please remember that all finite-element-methods are approximation methods. The quality of the approximation increases with increasing mesh density. In the current version, systems with a maximum of 225,000 triangular elements and 225,000 nodes can be analysed.
Several examples from the literature are saved on disk (Zienkiewicz and Schwarz). Recalculation shows almost complete agreement.
The short description shows that only a few menu items need be selected for analysis. All further menu items are mainly for data saving, layout and, if necessary, further evaluation of analyses. A description will follow in the further chapters.