Understanding Subassemblies

Overview of subassemblies.

Subassemblies are predefined components of assemblies within Civil 3D. Civil 3D comes with dozens of predefined subassemblies included in the product libraries. These subassemblies can include lanes, curbs and gutters, sidewalks, ditches, berms, daylighting, and many other options.

To access these subassemblies, on the ribbon, Hom e tab, Palettes panel, click the Tool Palettes button to open the Tool Palettes. The Tool Palettes that contain subassemblies are just like any other Tool Palettes within AutoCAD.

To look at some of the subassemblies that come predefined with Civil 3D, on the Assembly-Imperial tab of the Tool Palettes, you can see some common assemblies such as a PrimaryRoadFullSection, SecondaryRoadFullSection, Basin Assembly, Divided Highway and more. Some of these predefined assemblies may work well for your project, and some may not. If they do, great. But you may also need to define your own assemblies based on the subassemblies that come with the product. To look at some of those, click the Basic tab on the Tool Palettes. On this tab, you have a list of basic subassemblies that include BasicLane, BasicShoulder, BasicCurb, BasicCurbAndGutter, and more.

There is also a tab for Lanes that has several specific lane subassemblies; and another tab for Shoulders; tabs with collections of Medians and Curbs; and a Daylight tab that has many different ways that you can apply daylighting to your assemblies. Along with those tabs, the Generic tab provides links and points that you can add to subassemblies to construct almost any figure that you would want. There are also Conditional subassemblies, and sub-assemblies for Trench Pipes. At the bottom, click the overlapped tabs and a flyout appears that lists all the subassembly tabs. You can see additional tabs for Retaining Walls, Rehab, and Bridge and Rail. These contain specific subassemblies for those items. The Rehab tab holds subassemblies for road rehabilitationthat can help with things like overlays, milling, and widenings.

Begin on the Basic tab and selectthe Basic Lane subassembly. By selecting any subassembly, the Properties palette appears. At the bottom are the parameters. Under Parameters, you can configure things like the side of the road that the subassembly will be placed on, the width of the subassembly piece, and the depth and the slope of that basic lane. The basic lane subassembly is a fairly simple subassembly, with only a few components and parameters that you can change. Press ESC to exit out of the BasicLane subassembly.

To look at something more complex, select the Daylighting tab and then select DaylightBasin. In the Properties palette, you can see a much larger list of parameters that define the daylighting basin subassembly. There are different depths, slopes, and different scenarios.

Any time you want to find out more information about your subassemblies, you can access the help system for that specific subassembly. Right-click the DaylightBasin subassembly and select Help…. In the Help window, you can see a diagram of the daylight basin subassembly, as well as a description of all of the input parameters. You can leave this window open so that as you change the parameters in the Properties palette, you have a reference tool that helps you understand what some of the parameters are. When you are done, closethe Help window.

Again, select the Basic tab and then right-click the BasicLane subassembly and select Help. In the help window, you can see the parameters that match what you see in the Properties palette. You can also see if there are any target parameters. This particular subassembly has no target parameters, however, some of the more complex subassemblies will. Target parameters allow you to target different Civil 3D objects. For instance, a lane subassembly might have a target parameter to attach a horizontal Alignment or a polyline. This would stretch the lane out to add features like turning lanes, bus lanes, or transitions to the lane. As you scroll down in the Help window, at the bottom, you can see a diagram of the basic lane, as well as a list of point, link, and shape codes. On the diagram of the lane are the point codes P1 through P4 at each corner of the polygon shape. Each of those points has a unique code applied to it that is available if you were to extract points from your corridor later on.

The links or lines between the points are also coded, such as L1 across the top. L1 is coded as the topof the assembly, andL3, which is across the bottom, is coded as the datum. Later on, you can use these top and datum codes in your corridor to build surfaces from. The diagram also has a shape code, since a complete closed polygon is made between all the point and link codes, it results in one shape code. A shape can be filled with hatch. For example, you may want your lane to have a concrete or an asphalt hatch applied to it. You would designate this in a style that is then used in the code set for the assembly that this lane is attached to. Then, the lane piece would show up with the hatch you selected. For this lane, the shape code is S1. The shape code is also used during volume calculations.

Take some time to explore these subassemblies. Right-click different ones you may be curious about and look at the Help file to understand exactly how they work and which ones may be best for your project. Civil 3D comes stocked with so many subassemblies to use, you will certainly be able to find one that you can use as-is or modify for your particular needs.