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Load combination

WinTess is a program for calculating and non-linear analysis. The meaning of this is explained in the blog: Non-linear Analysis

This implies that when combining different types of loads, we can not add the results of each type (hypothesis of load), as we do in the calculation and analysis of other types of structures: steel, concrete, wood, etc. These combinations of results, also allow you to use different safety factors for finding the most unfavourable combinations and sizes accordingly. But, this is not possible with membrane structures with large displacements,

Combinations

To create a combination of loads, we can use two menus File | New | Loads combination or Calculate | Loads combination. The first menu is always available to the user, while the second is only available when Calculate menu is visible.

load-combination-menu1load-combination-menu2

Before using this menu, which allows us to perform a load combination cases, we must have done various calculations, separately, with different loads, grouped or individual, for example:

Case 1 : Self weight and prestress
Case 2 : Case 1 + wind in +X direction
Caso 3 : Case 1 + wind in -X direction
Caso 4 : Case 1 + wind in +Y direction
Caso 5 : Case 1 + snow
Caso 6 : Case 1 + wind in +X direction + snow
Caso 7 : Case 1 + wind in -X direction + snow
etc.

In each of these cases, we apply different safety factors coefficients to the loads, depending on the type of grouping. To do this we need to comply with construction regulations of each particular country.

Once the menu is selected, the hypothesis selection window appears. First let’s enter a title to the combination “title” box. It is convenient to use terms referring to the work under consideration.

Then click the button Choose the files to combine and file selection window appears. All the files you want to combine have to be in the same folder. You can select multiple files at the same time, not one by one. We can also add files as many times as necessary. If we have added a file that we shouldn’t, pressing the mouse button will present us a small menu that allows us to delete that file.

load-combination1
load-combination2

With this menu, we can also check if the file is suitable to combine. That is to say, this is a file of calculation, not of form finding or patterning.

Once you have selected all the files, it is appropriate to give each one of them an identification ID, as shown in the image on the left: L0, Snow, Wind Y.

When finished, we click on Combine.
load-combination-errorBefore combining different files, the program performs a series of checks:

  1. If all files are in the same folder.
  2. If all files are of calculation type.
  3. If number of nodes, bars and elements match.
  4. If the type of nodes, bars, etc. match
    etc.

If an error is found, the program informs and does not go ahead until the file in question has been amended or deleted.
If there are no errors displayed, the combination results window appears.