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Modeling tangential intersections

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Modeling tangential intersections

Modeling tangential intersections.............................................................................. 1

Why tangential contours? ............................................................................................ 1

In Tekla Structures ..................................................................................................... 3

Modeling tangential intersections

Why tangential contours? 1

Modeling tangential

intersections

Why tangential contours?

Kersten Europe bv has years of experience in rolling plates and profiles. The way

in which customers deliver their product information, determines the quality, cost

price and time of delivery of the product. Providing correct product information will

not cost extra time for the customer, but they need to know this beforehand.

This article is interesting for you if you want to bend straight profiles or plates with

straight ends or with multiple radii.

What is tangential?

If you want to use a profile with a straight end, you need to connect this straight

end tangential to the radius. If not, differences in dimensions are caused which can

be quite high in size, as described later on in figure 2.

An example of what the differences are:

The following example shows a drawing of a bended box girder with a straight end,

as we received:

Figure 1

At first glance, it all looks good. However, if a bending company starts bending with

this information, it creates a box girder with a bended contour according to figure 2.

In figure 2, the drawing has been placed on top of the bended profile.

Wrap a rope around a cylinder and pull it tight. The rope

will gradually change from the straight part to the circum-

ferenceradius of the cylinder, wherein the intersection

point is perpendicular to the center of the cylinder. This

intersection is called tangential.

2 Why tangential contours?

Figure 2

As you can see, the end of the bended product is not in the position mentioned on

the drawing. The difference amounts to 84 mm. What causes this difference and

how to prevent this?

We check the drawing by creating a line from the center point of the radius to the

end of the radius and we measure the angle between this line and the straight part,

we see that this angle is 88°. This means that the straight end is drawn buckled.

Figure 3

To bend the box girder according to the desired contour, Kersten Europe will adapt

the original drawing whereby a tangential geometry is determined.

Figure 4

In figure 4, the intersection point from the bended contour to the straight line is

moved 260 mm. This means in practice that the bended product is not equal to the

original drawing anymore. As far as the contour you will not see this difference in

practice. However, this might cause difficult problems if connections are required

on the beam afterwards, because in practice you will have a shorter straight part

than expected, according to you own production drawing.

To avoid this, it is important to create the intersection points tangential from round

to straight and from round to round. You will get what you expect and there are no

extra costs for re-drawing afterwards.

How to create tangential intersection points in Tekla Structures will be explained

next.

In Tekla Structures 3

In Tekla Structures

In Tekla Structures you can model curved beams and plates. This could be a

simple contour containing 1 radius and 1 straight leg or 1 radius and 2 straight

legs, for example, see the following examples:

There are also a lot of contour-combinations possible:

To improve the exchange of information and to make sure that these kinds of

contours can be bended perfect, whereby no differences in dimensions occur and

double work is prevented, these contours must be modeled "tangential".

It means that the leg (or the legs) must be modeled perpendicular on the radius of

the polyprofile, see the following picture:

4 In Tekla Structures

In detail:

In the example above, several construction circles- and lines are modeled (check

the brown-colored construction line perpendicular to the radius).

Because of this, the polyprofile can be modeled in a correct way and whereby the

points (yellow and magenta) are positioned on the construction line, see the

following example.

Always make use of suitable construction circles- and lines in Tekla Structures to

model polyprofiles and plates in a correct way.

In Tekla Structures 5

In Tekla Structures you can export drawings of curved profiles and/or plates to a

DWG- or DXF-file.

For this purpose, select in Tekla Structures in the drawinglist the concerned

drawing(s), right-click and select the command Export. If desired, you can edit the

settings in the dialogbox Export Drawings, next click Export.

In the exported drawings, the arcs of the polyprofiles are displayed in real, not as

segmented lines.

Drawing in Tekla

Structures

The exported

drawing

6 In Tekla Structures