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# [CIM/Rebar] Operation of Offset and Part Length in Rebar Property

## Question

I wonder how Offset and Part Length are applied in CIM.

Part Length is applied as the distance from the intersection of the center of the reinforcing bar to the end of the reinforcing bar.
Offset is applied as the distance from the end point of the rebar in the +/- direction of the vector after applying the Part Length.

Info

This document deals with each operation of Offset and Part Length in the Property of Transverse Rebar.
Accurate rebar modeling work can only be done by clearly understanding the properties of the two properties.
Offset and Part Length are values ​​that define information about length among the shapes of rebar to be created.
The information defining the rebar alignment shape is given below.

Information Defining the Shape of Reinforcing Bars

In CIM, the rebar shape is based on the line, and the information to define the rebar shape is as follows.

Draw point
: the reference point of the object used to draw the reinforcing bar.

Hook
: Rebar hook shape information.

Cover
: The distance from the line connecting the draw point to the reinforcing bar.(cover)

On Plane Cover Align Center
: Turn on/off the function to set whether the reference line is the center of the rebar or the outermost corner of the rebar.

Offset
: length adjustment value of both ends of reinforcing bar.

Part Length
: The length of the bending area at both ends of the reinforcing bar.

First, let's look at how Offset works through pictures.

 Figure. 1 Offset Length - 1 Figure. 2 Offset Length - 2

The blue line is the shape of the reinforcing bar before applying Offset and Part Length.

As shown in Figure 1, Offset is information mainly used when defining the cover from both ends of rebar to the concrete surface.

On the other hand, as shown in Figure 2, it can be used in various cases. To explain this function accurately,
Offset is a property that operates after Part Length is applied . It is length adjustment information from the end point of the rebar to be drawn in the Vector +/- direction.

Therefore, it can be used when you want to adjust the length of both ends of rebar in various shapes drawn with Free Shape.

Tips

In the Property, the order of function is applied in the order of ① Part Length - ② Offset - ③ Hook
For example, when Part Length and Offset are applied at the same time, the final length is calculated by applying the length of the reinforcing bar as much as
① Part Length value, and then applying
② Offset value.

Next, let's look at the operation of Part Length.
The reinforcing bars below are created by selecting the edge in the direction of the red arrow using the Select Member Edge function of the Transverse Rebar.

 Figure. 3 Operation when Part Length is positive/negative Figure. 4 Operation when Part Length is '0'
 Figure. 5 Part Length Calculation

Part Length Property can be checked on/off.

Only in the case of Check on, it affects the area after the final bending. If you look at the picture above, you can see that it operates in different ways when the input Part Length value is positive / negative / 0.

Each result is shown below.

Classification of Actions According to Start/End Part Length Values

Info

Depending on the entered Length value, the function operates in three ways.
Positive : Define the length in the forward direction of rebar progress.
Negative : Define the length in the reverse direction of the rebar advance.
0 : Do not draw the area of Start/End Part. (The length of the bending area at the end is '0')

let's take Figure 4 as an example to make it easier to understand the case where the Start/End Part Length is 0.

 Figure. 4 Operation when Part Length is '0'

Let's take Figure 4 as an example to make it easier to understand the case where the Start/End Part Length is 0.

Figure 4 shows a case in which Start/End Part Length is set to 0.
The shape information originally possessed by the reinforcing bar is entered as a C shape with two bendings like Line.
Here, Part Length works to eliminate bending on both sides and the final rebar shape is created like a straight rebar.

The point to be noted here is that even reinforcing bars that look the same have a big difference in terms of information depending on which property they are combined with.

Tips

Part Length Rules
The value of Part Length does not mean the length from the end of the curved part, but the distance from the intersection of the center of the reinforcing bar to the end of the reinforcing bar (before applying the offset).
That is, even if the Bending Radius value is changed after setting the Part Length in the Property, only the curvature is changed and the end point of the reinforcing bar is not changed.

The example below is the rebar array result of the side section section depending on whether the part length is used or not.

 Figure. 6 Draw Type  Select Member Edge / Start Part Length “0” Figure. 7 Draw Type Select Member Edge / Start Part Length “off” / Start Offset (-80mm) Input Figure. 8 Start Part Length “0” > Array Result Figure. 9 Start Part Length “Off” > Array Result

If you look at the example above, you can see that the shape of the rebar in the Start Plane is the same, but the shape of the two rebar groups gradually changes as they are arrayed.

Although the reinforcing bar in Figure 6 has 5 edge reference information along the direction of progress, it is a shape in which the bending area at the beginning is removed by defining the Start Part Length as “0”.

At this time, the bending area disappears, but the information to be referenced is still maintained.
From the top of the box, you can see the result that the value defined as Cover Thickness is continuously maintained as the end cover of the rebar.

On the other hand, the reinforcing bar in Figure 7 is a shape in which only 4 edges are referenced and the length is extended by inputting an offset of “-80mm” from the starting end of the reinforcing bar.

In the case of reinforcing bars made in this way, it responds to changes in the edge of the abdomen of the box. A rebar group is made of reinforcing bars that are extended by -80mm from the edge.

In this case, the box top surface and the reinforcing bar do not have any relationship.

Therefore, it is necessary to draw the reinforcing bars desired by the user through appropriate property settings in various situations.

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