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Menu: Bars

This is the basic menu for dealing with bars.

It is interesting to remember that one bar is a straight segment that runs from one node to another node in space, therefore intangible.


Create a new bar

Having activated this menu, the following submenu appears:    

  1. With pre-existing nodes
    The mouse cursor will change into selection finger to select the node as the origin of the new bar that we wish to create. Once clicked on the first node (must be highlighted with magenta color), a red rubber band appears to accompany the movement of the mouse until you press on the end node (must be highlighted with magenta color). The bar has been created. WinTess assumes that you are going to create another new bar next, so that the end node of the previous one becomes the first node for the new.
    If you want to start the new bar from another node, click the mouse right button.
    If you no longer want to create another new bar, click again the right mouse button on a blank area and the process is terminated.
  2. With new nodes
    bar-create2As shown in the window on the right, we can enter the coordinates of the first node of the bar and the second node. If you like, you can click on an existing node to get the coordinates of that node in the corresponding boxes. Then, you can modify any or all of the coordinates in order to create a new node. If there is a node at these coordinates, WinTess uses that node, if not, creates a new one. Once you have created a new bar by pressing the OK button, the bar is incorporated into the structure. Then, you can edit its properties.

Edit

Editing a bar means modifying some of the properties of the bar which appear in the editing window. We can edit a single bar or more, as long as the properties we are going to modify are the same for all these bars.

To edit a single bar press the right mouse button on the bar (it must be highlighted) and second submenu of the pop-up menu takes us to editing window where we see all the data corresponding to the bar in question.

Another way to edit bars is to directly use the menu Bars | Edit. Once this menu selected, the mouse cursor becomes selection finger that enables us to select the bars we wish to edit. We can do it one by one or by a window that embraces them. The selection is ON/OFF type, i.e. if we pick a bar already selected, we deselect it. During the selection of bars by dragging the window, we can move on and continue with the selection. Once we finish selecting the bars, we press the right mouse button and see the window shown in the above figure where we modify the values that affect the bar or the bars selected.


The data that we see in the bar edit window can vary depending on the state of WinTess or depending on the type of bar that we are editing. In the Analysis state, it often presents more data than in the other states because what is not necessary is not visible or if it is, not enabled. If not in Analysis state, editing window is much simpler.
In form finding, editing window is the first of the following images. Type of bar, end nodes and Stiffness are the elements to be edited. The last one (stiffness) is very important when form finding.
In patterning (second image), there are still less elements to be edited, since stiffness, in this case, is not at all important.


  • Box to enter the number of bars
    This box is always active and can be modified at any time in order to add or remove bars from the selection. If we modify these values we can observe how it automatically select the bar (in red) on the main screen graph. (See IMPORTANT NOTE below)
  • Grup
    In this drop down box we see the bar groups. If we select one of them, the numbers of the bars in the group automatically appear in the bar number box and are selected in the main screen graph.
  • Type
    In this drop down box, we choose the type of bar that will apply to the bars edited. Depending on the type of bar selected, the window shows or hides some editing controls and also changes the units to applicable ones. As we have already discussed, this also depends on the state of the program .
    • If we choose the type 1 (membrane) in the state of Analysis, two options appear just below the type drop down box: warp and weft. The first is the default option. These options are very useful when working with membranes ortotropic (with different characteristics depending on perpendicular axes).
    • If we choose any of the types 0 (Tube), 2 (rigid bar), 5 (boltrope), 6 (guyrope), we see another drop-down Def. on the left. This control connects us to different databases of WinTess. Picking one of the options here gives us  In the pick any of the options they give us the different databases of the program.
      In the case of type 2 (rigid bar), we observe how the window is enlarged by the bottom and appear new data.
    • It is recommended not to use the type 4 (diagonal) since this type is mapped directly to the program. Use it only if mesh is irregular where we create diagonals by ourselves.
    • The type 3 (fixed length) is an option which is currently not operational.

IMPORTANT NOTE:
If the bar number box is blank and the bar type is not blank, then all the bars of this type is modified at the same time. This option is very useful, for example, for when we want to modify all the cables or all of the tubes of a structure and make them all equal.

  • Def.
    This drop-down shows the databases of tubes and cables so that we can assign them to the selected bar. It is only visible in those cases that may be useful.
  • Factor
    It is a number that multiplies the value of the bar cross section. It appears only in cable type bars and serves to represent a group of cables that form the same bar. This is a real number value (you can have decimal places), but in general it is always be an integer. By default the value is 1.
  • Left node, Right node
    Normally we never modify these values, but in some cases we can modify the position of a bar by modifying the end nodes. If we do that, we have to update the structure entirely in order not to generate strange forces due to the change in geometry.
    If we edit more than a bar at the same time, most likely, none of these nodes have in common and therefore the boxes will be blank.
  • Prestress (%dL)
    The most common thing is that we prestress only membrane. However, WinTess3 allows prestressing any bar. We must keep in mind that prestressing bar is entered in %. If we want to know the prestressing force F of bar, we use the formulae listed below related with tension-deformation

σ = ε · E
F = σ · A = (%/100) · E · A

    • And a steel pipe with E = 210 kN / mm², a section of 500 mm² and a prestress of 0.1% would create a prestressing force of 0.001 · 210 · 500 = 105 kN.
  • Li, Lf, Axial
    Initial length, final length and axial force are informational values of the edited bar (cannot be modified). If there is more than one bar, quite commonly, these values will be blank since the values will not be the same for all of the bars. However, Li can be modified in some cases: in the Analysis state and for the bars that do not represent the membrane. Modifying this value may affect the Analysis significantly, it is convenient to use this option when you have a clear idea what you want to do.
    In addition, sometimes the option box LiLf appears above Li.
    This option nullifies any prestresing force that the bar has since the initial length of the bar is made equal to the current length, the axial force on the bar becomes zero.
  • E
    Modulus of Elasticity of the material. This value cannot be modified as it is determined by databases of tubes, cables, or membranes. Only, in the Form finding state, this value is accessible. In this state, it does not mean the real modulus of elasticity, but only a relative value which, by default, is 1 on the mesh bars and 5 on perimeter bars. But user can (and should) change it to get the desired form.
  • Density
    This is also an informative value that cannot be changed since it is determined by databases of tubes, cables, or membranes.
  • A
    Section of the bar. For the bars that represent membrane (types 1 and 4), the section is measured by the width of the membrane that represents each bar of the mesh. Normally this width can be calculated automatically by WinTess3, but if we want to have a close control on the width, we can modify the value of A in the Analysis. For the other bar types, this is an informative value that cannot be changed since it is determined by the databases of tubes or cables.
  • Temperature
    These values allow you to simulate a thermal load on the bars. (It is possible that, in the future, these data will no longer be a part of data of the bars and are implemented as external loads to the structure).
    dTemp = increase or decrease in temperature of the bar
    Thermal expansion coefficient = The name itself defines it.
  • bar-rigidRigid bar
    Only in the case of Type 2 bars (rigid bar), we see the following box at the bottom of the bar editing window

On the left, we have a few buttons to define the type of the end nodes of the rigid bars.
On the right, we have the information about the moments of inertia of the rigid bar selected. These are values only for reading, because they come from the database of tubes.


Copy/Move

As the name of the menu itself indicates, it is used to copy (replicate) or move a group of bars that are selected in the usual way: one by one or through a window.
Once the bars have been selected we click the button of the right of the mouse and we obtain the window on the right hand side:

1. First we decide if we want to copy or move the bars. (radio buttons)

2. Then we set the starting position of the movement. You can enter values ​​in the X, Y, Z boxes of the “From” column or select a node on the screen to choose its coordinates. If we do not enter anything equals the point 0,0,0.

3. Next we do the same with the values ​​of the boxes X, Y, Z of the column “To”.

4. We can decide whether to copy or move bars we want to unify the knots at the end. In that case we can even determine what will be the precision to unify the knots. We can, as well, Purge nodes at the end (delete nodes that are not useful).

5. Finally click the “Cancel” button to leave things as they are or “Ok” to perform the operation of copying or moving bars.


Initial data

The program displays a table of initial values for the bar. In the second row, we see the units of the values in the table.

Bar: Bar number

N-1, N-2: Nodes that define the bar. (By default the first one N-1 is considered the left and the second the right node of the bar).
Type: Type of the bar
Li: Initial length of the bar
A: Section of the bar
Axial: Axial force on the bar. (In fact this is a final value, since it involves a calculation)
E: Modulus of Elasticity of the material that forms the bar
Pret: Prestress applied to the bar
Weight: Weight of the bar (Li · A · Dens)
Dens: Density of the material that forms the bar
dT: Increase or decrease in temperature applied to the bar
alfa: Thermal expansion coefficient of the material that forms the bar


Final data

The program displays a table of final values for the bar. In the second row, we see the units of the values in the table.

Barra: Bar number
N-1, N-2: Nodes that define the bar. (By default the first one N-1 is considered the left and the second the right node of the bar).
Tipo: Type of the bar
Lf: Final length of the bar
A: Section of the bar. (In reality this is an initial value, because it does not depend on the calculation)
Axial: Axial force on the bar.
dL: Increase or decrease in length of the bar
Tension: Maximum stress by the section of the bar, due to the tension or compression (with sag calculated) and/or bending.
Ratio: Coefficient that exceeding the value of 1 means that the stress on the bar has exceeded the maximum calculated stress of the material that forms the bar. This maximum calculated stress incorporates a safety factor which encompasses both coefficients to escalate the loads and to reduce the resistance.


Rigid bars data

If the structure does not have rigid bars this menu is disabled. If there are rigid bars, it will display a table with the distinctive values of these bars. In the second row, we see the units of the values in the table.

Bar: Bar number
Axial: Axial force on the bar
Torsor: Torsional moment of the bar
M1Y,M1Z,M1T: Bending moments in the end N-1. In accordance with the local axes x,y,z of the bar, the table shows us the moment M1Y in the plane x,y, and the time M1Z in the plane x,z. Added vectorially, we obtain the total moment M1T.
M2Y,M2Z,M2T:Bending moments in the end N-2. In accordance with the local axes x,y,z of the bar, the table shows us the moment M2Y in the plane x,y, and the moment M2Z in the plane x,z. Added vectorially, we obtain the total moment M2T.
FY,FZ,FT: Shear stress in the bar. In accordance with the local axes x,y,z of the bar, the table shows us the shear FY in the plane x,y and the shear FZ in the plane x,z. Added vectorially treated we get the total shear force FT. If there is no loads on the interior of the bars, the shear forces are constant throughout the bar.
Ratio: Coefficient that exceeding the value of 1 means that the stress on the bar has exceeded the maximum calculated stress of the material that forms the bar. This maximum calculated stress incorporates a safety factor which encompasses both coefficients to escalate the loads and to reduce the resistance.


Automatic section

We have already commented that a section of a bar type 1 or type 4 (membrane) is measured by the width of the membrane that represents. This work is done automatically by the program when changing program state from Form finding to Analysis. However, throughout the process of Analysis, we can make changes that require to rebuild sections automatically. This menu is designed for this purpose. We can also manually enter this value via the Edit menu.


Relax bars

This operation is included in the Calculate | Reset menu (window), but  in some cases it may be interesting to perform this operation independently. With this menu bars have their initial and final length equal, so that there is no axial load in them.

This menu has two submenus:

  • All = Relax all bars
  • Select = Wintess lets us select the bars we want to relax. At the end, clicking the right of the mouse button we execute the action.

Delete by numbers

bar-delete-numbersThis menu is used to remove bars according to their current numbers. WinTess3 pops up a window that, besides some notes, allows us to enter the numbers of the bars that are to be eliminated. Automatically (if it was not on) bar numbers are shown on the screen so that we can see which bars are to be removed.


Delete graphically

The mouse cursor changes to selection finger so that we can choose the bars we want to delete. We can do it one by one or in groups in a window. We must remember the way of generating the window (to the right or to the left) and the ON/OFF selection method (if you select a bar already selected, we deselect it). Once the selection is done, click the right button of the mouse and accept or cancel deleting the selected bars.


Delete by type

With this menu we can delete “all” the bars of a certain type. We only have to check the corresponding box in this window.


Delete duplicate bars

It is not usual to have duplicate bars (that go from the same initial node to the same final node). Either due to a mistake in editing, or because they have been imported from a DXF file which already had duplicates or for whatever reason, this may happen. WinTess3 removes them automatically when reading a file, but if we have made many changes and doubt that we have duplicate bars, this menu may be useful.


Groups of bars

The possibility to gather bars in groups is something very useful and typical in the programs using bars. A bar group is a set of bars that share some characteristics. A bar can belong to more than one group or may not belong to any one.

By default, WinTess3 creates a group called “T” that includes all of the bars of the structure. In a transparent manner (the user must not do anything) if there are border cables in the structure (consisting in more than one bar) WinTess3 creates other bar groups for each cable called Cable n, where n is the number of cable. So, Cable 3 is the group of bars which includes all the bars that make up the cable 3. It happens exactly the same with bars in warp or weft direction, if they exist.
To facilitate the edition of the group of bars, those created by the user (they can be edited) appear with a blue background, while automatic groups (that cannot be edited) appear on a green background.

We can create as many groups of bars as we want and delete them (except groups that define the cables). To create a group press the New button and write in the first column, just where the cursor has gone, the name we want to define the group. Then, in the second column, write the number of the bars that belong to this group. We can write or select them directly on the screen, one by one or through a window.

To remove a group, press the Delete button, and following the instruction of the program, delete the name of the group. Although bars in the box on the right, are not deleted when we leave by pressing the OK button,  the bars of the group will be deleted.

Besides, there is the possibility to transform a group of bars into a Cable or a Polytube. In this case, me must click de row of the group to be transformed and the press the corresponding button. It is absolutely necessary for the group of bars to form a contiguous group of bars, otherwise an error message will be displayed.


Renumber bars

bar-renumberIf we have created a mesh with WinTess3, bars have the best possible numbers. But if we have imported a mesh from a DXF file or have created and deleted many bars manually in WinTess3, it is possible that the numbering of the bars is not correct and hinders the use of the program.

It is not necessary that we re-number all the bars. we can renumber only a few. First we must enter the number of the first bar that we want to renumber. For example, if there are certain bars in the structure that we want them to be the 8,9 and 10 (obviously in this moment they are not), we will enter the number 8 in the text box of the window and press the OK button.

If already not, it activates the numbering of bar and the cursor changes to selection finger. We mark over a bar and this number changes to take the value that we have introduced in the text box. If we continue checking other barc, number will increase one by one. Finally, as always, click the right button on a blank screen area.

Is clear that when we change the number of a bar, the current value is changed by the bar that we are going to renumber. If we select bar 25 , for example, and numbers is as 8, the old bar 8 now becomes 25.


Divide bars

bar-divideWhen you click this menu, the mouse cursor becomes selection finger. We select the bars that we want to divide, one by one, or through a window, and then click the right mouse button. WinTess3 asks us how many equal pieces we wish to divide the selected bars. We introduce a value ≥ 2 and click the OK button. Selected bars are now divided into equal pieces.
Attention:
Probably if you divide a “tube” bar, you should change the type of all the resulting bars into “rigid bar”, otherwise you would get a bunch of articulated tubes.


Locate a bar

Many times, we need to know where a specific bar is to assess the results, to edit, etc. When the structure has many bars, this cannot be done easily with the naked eye, looking at the screen. So, WinTess3 provides a tool for that. Through the window as seen on the right, we enter the number of the bar that we want to locate. As soon as we press OK, the bar in question immediately appears on the screen with red color.bar-locatebarraRoja

Local axes

This menu is only operative if there are rigid bars in the structure. The rigid bars may have moments, torsion, shear forces, etc. in two main directions, perpendicular to each other and perpendicular to the local "x" axis that coincides with the own guideline of the bar.
WinTess3 draws "y" and "z" on the central point of each rigid bar axis, using the same colors used to draw the principal axes X, Y, Z at the bottom left of the main screen.EjesGenerales
EjesLocales