Before we begin patterning of a structure we must take various aspects into account:
State of the program
We have already mentioned that WinTess3 is a program “all-in-one” type suite with very clear three states of the program. In order to make a pattern, it is necessary that the program is in the state of Patterning, so we need to update using the drop-down from top toolbar.
If we open a file saved previously, WinTess3 remembers what state the program was in when it was saved and puts us in it. Now whether we are designing a certain structure is very possible that we have started with form finding. Once it is done, we wish to pass to the stage of calculation or directly to the patterning.
If we update the drop down from top toolbar we get a message which reminds us that:
- The pattern depends on the initial form of the membrane. If we come from form finding, the initial form of the membrane is what you have. In fact, it is the final form of the Form finding phase.
- If we come from the calculation phase, what we see on screen is the final form (deformed). The program will automatically return it to the initial form, i.e., before the deformations caused by the loads (even before the prestressing of membrane). The results of the calculation will be lost, unless:
- WinTess3 suggests storing the results of each phase in a separate file. If we are coming from the calculation phase, WinTess3 suggests _calc in the end of the filename in saving filename.
Once we are in the phase of patterning, we can start with the following process:
- Define the effective width of the membrane
Membranes used in tensile architecture are usually supplied in rolls of variable width. Typically this width ranges between 1.5 m and 2.5 m, but there are wider membranes as well. These wider membranes are useful for projects with flat surface (such as the cylindrical part of a membrane system supported by air) or for huge warped surfaces (cover of a stadium, for example).
Sometimes you choose to use a very wide membrane for economic or logistical reasons, but it is used as if half width placing the patterns one beside the other.
- Decide where and how patterns will be placed on the membrane
This is a doubly important decision: on one hand we have aesthetic and the other one is the constructive.
If the membrane is opaque, we almost never perceive the pattern when we look at the membrane. Now, if the membrane is translucent, as it is most of the time, the pattern is clearly seen from the darker side; from the inside during the day and from the outside during the night if the interior is illuminated. In these cases the distribution of the pattern design is extremely important for aesthetic purposes.
- Attach the end points of the patterns along the perimeter
This is a work that can be very tedious if you’re going to get patterns that have a true width (flat) very accurate. Especially if the membrane has a big curvature, the dimensions change when transposing the pattern from the warped membrane to plane,
In this sense, it is very useful to have assist points on the perimeter. The menu Auxiliary | New enables us to pick the Point mode and go marking on the bars perimeter points that can serve as an end point for the patterns (see the Geodesic lines).
- Draw geodesic lines
Once the end points are defined, we should draw geodesic lines through the menu Geodesic | Create geodesic. We mark the end points and define the number of parts to draw the geodesics. This is an iterative process that may take more or less time depending on the case. At the end drawn the geodesic lines will be shown on the membrane. In case of any problem or error, the geodesic obtained will be clearly somewhat out of place.
- Define the pattern triangles
Then, more tedious the pattern creation task begins: triangularization. An exclusive section in this manual is dedicated to this task. But it must be kept in mind that the more automatic the process of defining the triangles (in fact, to define the pattern), the less control over the patterns we’re going to have. We must therefore bear in mind that this process can yield very different results according to how it is done, like strange shapes at the edges or very curved patterns.
Therefore the ability of the user in choosing the triangles can be determinant of a good pattern in patterning with more difficult cases.
- Check patterns
Finally we pass to drawing patterns. This task serves not only as a tool to produce planes that are given to the manufacturer, but also serves to ensure what we have produced is correct.
In general, there are several reasons why we consider that a pattern is not correct and should be deleted and we return to creating patterns.
- We have created the triangles in bad order. The pattern is clearly deformed.
- The pattern does not fit within the width of the membrane. Do not forget the necessary margin (offset) for the welding seams.
- The number of points (triangles) used to generate the pattern is insufficient and, therefore, the perimeter of the pattern is not a smooth curve but a broken line.
Finally, if the result obtained is not as expected for whatever reason, we should repeat the necessary step of the process.