Free-Form Steel Bars in Revit: A Comprehensive Guide

Free-Form Steel Bars in Revit

Free-form steel bars in Revit allow for variable, non-planar distribution that can fill the surfaces of irregularly shaped structural elements.

By specifying reference surfaces and defining rebar properties along the main body and layout of the rebar set, you can place free-form reinforcement within any planar or complex 3D structural element. It’s important to note that free-form steel bars behave differently from shape-controlled steel bars when modeling detailed designs, maintaining parametric accuracy and preserving the geometric form of the model.

Free-form steel bars fall under the category of structural steel bars and inherit all related attributes. You can create a single steel bar or an entire steel bar set, including commonly used attributes such as hooks, quantity, individual bar length, total length, and automatic numbering. Additionally, free-form steel bars can be added to components and groups.

Placing Free-Form Steel Bars

Free-form steel bars can be placed onto concrete elements with simple geometric shapes, either on a single surface or across multiple surfaces. This example demonstrates how to place free-form steel bars in a 3D view.

1. Go to the Structure tab → Reinforcement panel → select Steel bars.
2. Click Modify | Place Reinforcement → Placement Method panel → choose Free form steel bars.
3. Ensure that in Modify | Place Reinforcement → Reinforcement Set Type panel, Surface distribution is selected.
4. Make sure Multiple Choice in the Modify | Place Reinforcement → Multiple Choice panel is not selected.
5. In the Attributes panel, specify the steel reinforcement type.
6. Set the layout in the Steel bar set panel.
7. In the drawing area, select the surface of the element to serve as the main body for the free-form reinforcement.
8. Select the reference surface adjacent to the main surface where the free-form steel bar set will start.
9. Select the reference surface adjacent to the main surface where the free-form steel bar set will end.
10. The steel bars will fill the main surface according to the reference planes and the predefined attribute settings.
11. Press the Esc key or click Modify | Place Reinforcement → Mode panel → Cancel to exit the free-form steel bar placement mode.

Placing Free-Form Steel Bars Along Multiple Curved Surfaces

Best Practices for Free-Form Steel Bars

When placing free-form steel bars, consider the following guidelines to ensure accurate modeling.

Passing Through Convex or Concave Edges

Free-form steel bars cannot pass through convex or concave edges between two main surfaces. However, you can use steel bar hooks to fill these convex or concave areas, adjusting the hook length and angle as needed.

If the angle between faces is not 90 degrees and the edge is convex or concave, the steel bar must be bent at various angles. In this case, create multiple steel bar sets (as illustrated in figures ① and ②) and modify the hook lengths and angles accordingly.

You may also utilize geometric shapes or work planes to draw individual shape-controlled or free-form steel bars at the intersections of main surfaces.

Passing Through Multiple Segmented Edges

Similar to convex and concave edges, free-form steel bars cannot cross multiple segmented or straight edges between main surfaces. These segmented elements should be divided into individual surface edges. For example, a graphic element can be split into three line segments, creating three separate surface edges to place free-form steel bars accordingly.

Drawing Free-Form Steel Bars

Free-form steel bars can be sketched directly in both 2D and 3D views. When sketching, the layout is fixed as a single bar, and constraints cannot be changed.

Before drawing, create and set a work plane aligned with the geometry of the main body, and draw steel bars on this work plane.

1. Go to the Structure tab → Reinforcement panel → select Steel bars.
2. Click Modify | Place Reinforcement → Placement Method panel → choose Draw steel bars.
3. In the drawing area, select the main body for the free-form steel bar.
4. In the Attributes panel, under Construct, set the Geometric Shapes parameter to Free form.
5. Ensure Sketch Mode is enabled and the steel reinforcement’s protective layer line is visible.
6. Use the tools in Modify | Create Reinforcement Sketch tab → Draw panel to sketch the steel bars directly.
7. When drawing, make sure to align lines with the main protective layer. Overlapping lines will coincide with the reinforcement’s geometric shape.
8. After completing the sketch, click Modify | Create Reinforcement Sketch tab → Mode panel to finish.
9. The free-form steel bar geometry will be created on the main body as drawn. Adjust its properties as needed in the Attributes instance properties palette.
10. To convert free-form instances into shape-controlled steel bars, go to Construct and set Geometric Shapes to Shape control. Shape-controlled steel bars can then be constrained and distributed in sets within the main body.

Related Skills

Placing Free-Form Steel Bars in Revit for Alignment and Distribution

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