About Free Form Reinforcement Shape Matching

Understand the rules for rebar shape matching when detailing with free form rebar.

Free form rebar instances match existing rebar shape families or create new shaped for matching rebar geometry. Each bar in a set is subjected to this matching procedure, allowing common fabrication data to be extracted for scheduling. While rebar shapes are common to both shape driven and free form rebar, there are some differences between the two.

• Shape driven rebar is defined by a common shape family.
• Free form rebar geometry is defined by selected references and matched to shape families where applicable. Otherwise, it creates its own shape that matches that same geometry.

Numbering and assembly matching properties of structural rebar make use of the shape information, such as shape codes and segment lengths, when encountering a free form rebar matched to a rebar shape family.

If each rebar in a set is planar and can be sketched according to rebar shape family rules, then it can be matched to a rebar shape. If a matching rebar shape exists in the project then the rebar is matched to it, otherwise, a new rebar shape family is created.

Planar free form bars with hooks rotated outside the bar plane will match to rebar shapes with a compatible hook rotation.

Rebar Shape Family Rules

For free form rebar to be eligible for shape matching, the planar geometry cannot end in an arc, have consecutive arcs along the bar, and all arcs must be tangent to adjacent straight-line segments, without exceeding 180 degrees.

Geometry that is not allowed in rebar shape families

• Shaped ending in an arc.
• Consecutive arcs.
• Arcs not tangent to adjacent segments.
• Arcs greater than 180 degrees between adjacent segments.
• Almost collinear adjacent segments.

Tip: To troubleshoot shape matching, use dimensions to highlight the individual bar segments or export the bars to a DWG file to analyze the geometry if matching is not possible.

Workshop Instructions Parameter

Use the Workshop Instructions instance parameter for free form rebar to specify how it will be fabricated. Specify:

• Straight. The rebar is delivered as a straight bar to the site. The shape code is the first straight rebar shape loaded into the project (Rebar Shape: 00).
• Bend. The rebar will be matched and bent to an existing rebar shape. If a match does not exist, a new matching rebar shape is created.

You can assign a different shape to free form rebar which cannot be automatically matched to rebar shapes. To do so, create free form rebar and assign a different shape in the rebar instance properties.

Hooks and End Treatments

Both hooks and end treatments are used when matching the bar geometry to a shape if included in the rebar shape definition defined in the General Reinforcement Settings dialog.

Bars in the same set can match different rebar shapes. Although the set can have a hook at start, some bars in the set may be inverted to match their respective shapes.

Tip: Use rebar schedules to get hooks and end treatments assigned to each end of each bar in a free form set.

Note: Changes to the shape geometry will prompt the creation of a new shape if it no longer matches the geometry of the free form bar.