Understanding part orientation

Understanding part orientation can take some time to figure out – while modeling in Tekla can be accomplished by simply changing the parts to the correct position values through trial and error, having a good grasp of these concepts can help speed up productivity, and be an all-around better Tekla modeler.

First, we will explore some aspects of the Tekla model that affect the position of parts, and then tie these together with some examples.

Coordinate systems

There are different types of coordinate systems in Tekla – we will discuss Global and Local. The Global coordinate refers to the green cube you see in the bottom corner of a new model.
 

 

This indicates the default 0,0,0 location of the model, and the default X, Y, and Z directions. The Global coordinate is static and cannot be changed. It is mostly referenced during import and export operations from Tekla Structures.

The Local coordinate system is also known as the current active Work plane. It is represented both as a red coordinate arrow with the X and Y directions and as a 3D icon that also includes the Z direction.

 

 

 

 

 

The Local coordinate system has a direct effect on the positioning values in your beam and column properties in the property pane. A value used when the Local coordinate system is set one way will give completely different results if the Local coordinate system is moved or changed.

It is crucial that you are aware of your current Work plane/Local coordinate when setting the position properties of the parts you are adding to the model.

 

Reference lines

Parts in the model are located by a theoretical line between the start and end handles called Reference Line. This reference line is set by the locations of the handles in the model. Changing the position values in the part properties will move the profile around the reference line; it does not move the location of the reference line in the model.

All of the positioning properties are based on the reference line looking from the start handle towards the end handle.

Faces

Next we need to examine the concept of the part ’faces’. Not counting the ends, parts have 4 faces – Top, Front, Back, and Below. Below is an example of several profile types, and how Tekla views these faces.

Each of these is represented as if we were looking from the ’Start’ (yellow) handle towards the ’End’ (magenta) handle. I-profiles are upright, angles are in the letter L, with the longer leg vertical, channels have their toes facing to the right, and tees are upright in the letter T orientation.
 

 
When talking about part rotation, these are the settings you will find in the drop-down menu when these profiles are used as beams or columns. It is important to remember that the faces do not change if the parts are modeled in differently – if you roll a beam over on its side, the top is still the top, it’s just no longer facing up.

Example 1 - Beam orientation

For parts that are modeled with the beam tool, it is important to remember that all positioning settings are relating to the currently active Z direction. We will take a typical beam as an example, with the Local coordinate/Work plane in the default position.
 

 

Beam properties have position options of On plane, Rotation, and At depth.

 

• On plane controls the right-left position, in relation to the current Z plane. Its options are Middle, Right, or Left.
• Rotation gives the options Top, Front, Back, or Below. This is to control which side faces the positive Z direction.
• At depth controls the up-down position, in relation to the current Z plane. Its options are Middle, Front, and Behind.

In the image above, the On plane is set to Middle, the Rotation is set to Top, and the At depth is set to Behind.

For On plane and At depth values, it helps to picture a simple beam.
 

 

The dashed yellow line indicates the reference line, with the start (yellow) handle to the left and the end (magenta) handle further away. This sets up the Left and Right directions of the On plane setting. The image from the dialog box has the current setting to Middle, which centers the profile on the reference line.

The reference line also sets the location in the Z plane for the profile At depth value. Anything in the positive Z direction is considered in Front of the plane, anything in the negative Z is considered Behind the plane. The image from the dialog box is set to Behind – so this makes sure that the beam profile is set below the reference line, since the top of steel is what you are normally working from.

Rotation settings are simple to set which side should face the positive Z direction. With a default coordinate system where Z points up, the Top face should face the positive Z.

 

 

 

 

 

So, to quickly recap, with the default local coordinate system, the beam settings are On plane set to Middle, the Rotation is set to Top, and the At depth setting is Behind.

But what if the Local coordinate system is changed? Remember that the position values are directly tied to it – specifically the Z direction for a beam. The below images show the default coordinate and position values, and then the exact same beam with different coordinate/work planes. Notice that the position values are all different.

 

 

 

 

 

Physically, the beam is no different. It has the same properties for fabrication data exports like CNC/DSTV, and the drawings are not affected by the change in the local coordinate. You simply need to be aware of how this changes the required settings to model in a part a certain way.

Example 2 – Column orientation

For parts that are modeled with the column tool, the position is handled a bit differently. We will take a typical column as an example, with the Local coordinate/Work plane in the default position.
 

 

Column properties have position options of Vertical, Rotation, and Horizontal.

 

• Vertical controls the up-down position, in relation to the current Y plane. Its options are Middle, Down, or Up.
• Rotation gives the options Top, Front, Back, or Below. This is to control which side faces the negative X direction.
• Horizontal controls the left-right position, in relation to the current X plane. Its options are Middle, Left, and Right.

The following image is looking down at a column, with the currently active coordinate showing positive X to the right, and positive Y going up.
 

 

The line shown in red, the Vertical position, will always follow the positive Y direction of the local coordinate.

The line shown in blue, the Horizontal position, will always follow the positive X direction.

The next image shows the rotation face settings when viewing a column from the top. To help put this in perspective, remember that faces of the part are considered from the ’Start’ (yellow) handle, towards the ’End’ (magenta) handle. If you remember the face guide at the beginning, this shows that columns are modeled from the bottom up. Because of this, the front and back faces appear reversed when viewing from above.

 

 

 

 

 

Another image from a 3d perspective. Note the position of the handles – yellow (start) and magenta (end). This column has a current rotation of Front, that is, the front face is the one facing the negative X direction.

 

 

 

 

(Advanced) Z-direction and part properties

There are some exceptions to these rules.

The Z-direction can cause some confusion if aligned with the reference line of a beam (start handle to end handle), or if it is not aligned with the reference line of a column.

• If a part created with the Create beam tool is modeled so that:
  • The reference line is aligned with the Global Z direction, and
  • The start handle to end handle direction follows anything except the negative Z-direction of the currently active coordinate system;

Then column properties will be opened when editing this part, and those positioning settings apply.

If the current active coordinate system is set so that the start to end handle path follows the negative Z direction, then beam properties will be used to modify the position of the part.

• If a part created with the Create beam tool is modeled so that:
  • The reference line is not aligned with the Global Z direction, and
  • The reference line is along the Z coordinate (positive or negative) of the currently active coordinate system;

The beam properties will be opened when editing this part, but the positioning behavior will mimic that of a column.
 

 

The On plane field will mimic the Vertical position properties, and the At depth will mimic the Horizontal position properties (e.g. selecting Right will move the part Down per the Column Vertical properties).

 

 

 

 

 

In this situation, the rotation values are for which face is facing the positive X direction.

As a rule you should not work with the coordinates set in this manner to avoid confusion.

When working with beams make sure the coordinate system does not have it’s Z aligned with the reference line.

 

(Advanced) Rotation and drawings/CNC data

It is also important to keep drawing and CNC output in mind when changing the rotation of parts. If you review the section on part faces mentioned earlier, you can see that the properties do not change simply because a different rotation is selected in the part properties.

If you take a beam and set the rotation so that Below is facing the positive Z, it is effectively upside down – this may not make sense because a beam shape is the same either way in the real world, but when generating fabrication data, the software and the machine that is processing the beam needs to determine which side is ’up’.
 

 

The beam shown here has the rotation set to below, with bolts in one of the flanges. Since the software considers this to be the bottom flange of the beam, the bolt holes are represented this way in the DSTV file.