Characteristics and Utilization of Constraint Path

Summary	Understanding Constraint Path

Summary	Understanding Constraint Path
Related Function	Curve Library Mode : Curve Library > Constraint Entity > Path > Main Constraint Path Assembly Unit Mode : Assembly Unit > Constraint Entity > Path > Main Constraint Path (or Rigid Constraint Path⁭⁭ orSub Constraint Path )
Type	FAQ, Tip, Example

Q. Please tell me about the difference between Main Path, Sub Path and Rigid Path.

A. Main Path has the same rate of change as alignment,

Sub Path is a path that refers to the location of two specific points,

Rigid Path is a straight line that maintains a certain length and is regenerated in the upper mode.

Constraint Path linked to alignment has 3 Paths as shown below. The application of each path should consider the characteristics of the structure.

Types of Constraint Path and Main Features

Main Path
￭ Path defined by two constraint planes
￭ Interlocking with planar and vertical curve alignment / Path length variation
￭Example of applied structure
- Main Girder for PSC Box / Steel Box Br.
- Deck Slab / Median Strip / Side Barrier / Pavement etc.

Figure. 1 Main Path Concept

Figure. 2 Alignment Allocation of Main Path

Sub Path
￭ Path with both endpoints controlled by two constraint points (same point can be selected)
￭Alignment and Arc Path possible / Path length variation
￭Example of applied structure
- Cross Beam for Steel Box / PSC Beam Br.
- Cable for Cable Stayed Br. / Hanger Cable for Suspension Br. etc.

Figure. 3 Sub Path Concept(Follow horizontal path axis Option On)

Figure. 4 Alignment Allocation of Sub Paths

Rigid Path
￭ Path defined by one Constraint Point or Plane
￭ Only a straight line is available, and the path length is fixed
￭ Example of applied structure
- Precast Girder (PSC Beam / PF Beam…) etc.

Figure. 5 Rigid Path Concept

Figure. 6 Alignment Allocation of Rigid Path

Constraint Path input method and usage example

Let's look at the explanation of the input method of each path and the difference in the generation result when the Curve Library assigned to each path is assigned to a alignment through the example below.

1. Alignment Input and PSC Beam Curve Library

The Curve Library is created to automatically change according to the length of the allocated path by setting the position properties of all constraint planes to By Ratio.

Layout (Horizontal Alignment)
- Radius : 50m
- Total Length : 50m

Figure. 7 Layout (Horizontal Alignment)

Curve Library (PSC Beam)
- All Constraint Plane Alignment : By Ratio
- Total Length : 25m

Figure. 8 PSC Beam Curve Library

2. Input and Alignment Assignment of Main Path

Figure. 9 Create Main Path (Red Line)

Base > Library > Assembly > Create
- Name : Main Path
Assembly Unit > Constraint Entity > Space
- Space (Connected-1)
- Unit Length : 25.0m / OK(V)
Constraint Entity > Path > Main Path
- Select Constraint Plane : Select the starting point and ending point plane
- Offset (y) : 5.0m / OK(V)

Figure. 10 Assign Main Path of Curve Library

Assign Library > Curve
- Constraint Path : Select Main Constraint Path
- Select the created Main Path using the mouse / OK(V)

Figure. 11 Alignment Allocation of Main Path

Base > Assembly > Assign
- Select 1: Main Path in Select assembly unit
- Click Define path > Select segment and select the layout using the mouse
- Click the Add button in the Assigned list / OK(V)

When the main path is assigned to a alignment, it finds a alignment station according to the alignment rule of each constraint plane

It is a Constraint Path created by connecting them in correspondence with the alignment shape.

Figure 11 shows the regenerated PSC Beam Curve Library assigned to the 25m Main Path by maintaining the Offset (5m) curve assigned to the 50m alignment.

Therefore, the Main Path is a constraint path that is used for girder, deck slab, or barrier that follows an alignment whose shape changes along the alignment.

3. Sub Path Input and Alignment Assignment

Figure. 12 Create Sub Path (Green Line)

Base > Library > Assembly > Create
- Name : Sub Path
Assembly Unit > Constraint Entity > Space
- Space (Connected-1)
- Unit Length : 25.0m / OK(V)
Constraint Entity > Point > Point
- Location : 0.0m / Apply(+) / 25.0m / OK(V)
Constraint Entity > Path > Sub Path
- Select Start Point(0) and End Point(25) from Constraint Point
- Create (0,5), (25,5) Path using Direct Draw / OK(V)

Figure. 13 Sub Path assignment of Curve Library

Assign Library > Curve
- Constraint Path : Select Sub Constraint Path
- Select the created Sub Path using the mouse / OK(V)

Figure. 14 Alignment Allocation of Sub Paths

Base > Assembly > Assign
- Select 2: Sub Path in Select assembly unit
- Click Define path > Select segment and select the layout using the mouse
- Click the Add button in the Assigned list / OK(V)

When a Sub Path is assigned to an alignment, it first finds the position of the constraint point on the alignment and searches between them.

Constraint Path created by connecting straight lines.

painting. 14, the reference point of the Sub Path becomes the alignment starting and ending points, and from these points

This is a regenerated Path (Curve Library) with Offset (5m) as the starting and ending point in the orthogonal direction in the alignment direction.

Sub Path is the same as the cable of cable-stayed bridge, which is determined by the anchoring position of the starting point and the end point, and has a alignment constraint point (fixed position of the girder, the position of the pylon) and

Constraint Path used when assigning an object that has this location as a constraint.

Alignment Option of Sub Path

For reference, the sub path direction can be created in an orthogonal or parallel direction depending on the Follow path axis setting.

If Follow Horizontal path axis On,

If Follow Horizontal path axis Off,

4. Input and Alignment Assignment of Rigid Path

Figure. 15 Create Rigid Path (Blue Line)

Base > Library > Assembly > Create
- Name : Rigid Path
Assembly Unit > Constraint Entity > Space
- Space (Connected-1)
- Unit Length : 25.0m / OK(V)
Constraint Entity > Point > Point
- Location : 12.5m / OK(V)
Constraint Entity > Path > Rigid Path
- Check by Point in Reference location and use the mouse to select Mid Point (12.5)
- Coincident Point > Distance from ref. : Input -12m
- Length between coincidence : Input 24m
- In Extra length, Start and End : Input 0.5m
- Offset (UCS-Y) : Input 5m / OK(V)

Figure. 16 CAssign Rigid Path of Curve Library

Assign Library > Curve
- Constraint Path : Select Rigid Constraint Path
- Select the created Rigid Path using the mouse / OK(V)

Figure. 17 Alignment Allocation of Rigid Path

Base > Assembly > Assign
- Select 3: Rigid Path in Select assembly unit
- Click Define path > Select segment and select layout using mouse
- Click Add button in Assigned list / OK(V) Figure.16 Rigid Path assignment of Curve Library

Rigid Path finds the position of the Constraint Point (or Constraint Plane) when assigned to an alignment,

Based on the entered property, it is a constraint path that finds two points that maintain the set length (Coincidence Length: 24m) from the point and connects them with a straight line.

Therefore, the characteristic is that the length is maintained no matter what alignment it is assigned to.

Note that if the length of the alignment is less than the Coincidence Length, the path cannot be created because a matching value cannot be found on the curve alignment.

Rigid Path is a constraint path used when allocating an object whose vector changes according to a alignment change such as a beam of a PSC beam bridge, but its length must be maintained.

Figure. 18 Create Sub Path & Rigid Path (same location duplicate creation)

Base > Library > Assembly > Create
- Name : Sub+Rigid
Assembly Unit > Constraint Entity > Space
- Space (Connected-1)
- Unit Length : 25.0m / OK(V)

Sub Path creation is “3. It is the same as “Sub Path Input and Alignment Allocation”, and the difference is as follows.

Constraint Entity > Path > Sub Path
- Start / End Ref from Constraint Point. Select all Points as Mid Point (12.5)

Rigid Path creation is “4. Same as “Input and Alignment Assignment of Rigid Path”

Figure. 19 Sub Path & Rigid Path assignment of Curve Library

The assignment of the Curve Library is “3. Sub Path Input and Alignment Assignment” and “4. See “Input and Alignment Assignment of Rigid Path”

By assigning to each Path, the Curve Library is assigned redundantly at the same location.

Figure. 20 Alignment Allocation of Sub Path & Rigid Path

Base > Assembly > Assign
- Select 4: Sub+Rigid in Select assembly unit
- Click Define path > Select segment and select the layout using the mouse
- Click the Add button in the Assigned list / OK(V)

Sub Path is created based on one Mid Point (12.5), so there is no change in length even when alignment allocated.

Rigid Path first finds a virtual path in which the starting and ending points of the path matching the Coincidence length (24m) exist in a alignment form as shown in Fig.6 and the dotted line path.

The final path is created by applying the Offset value to this virtual path.

Therefore, in the case of Fig.20, the virtual path of the rigid path is located inside the alignment curve, and the alignment distance between the PSC beam and the alignment created by the rigid path is smaller than the Offset value.

If the sign of the radius of the curve is opposite, it becomes larger than the Offset value.

On the other hand, PSC Beam by Sub Path is from the regenerated Mid Point.

Therefore, in the Assembly Library, objects in the same location are created in different locations when they are assigned to an alignment.