## February 16, 2012

### ACA Structural Member Styles - Part 4

First Article in the Series (Structural Member Catalog)
Previous Article in the Series (Manually Created Structural Member Shapes - Fun Facts)

Manually Created Structural Member Styles
As we have seen in the first three articles in this series, there are a number of opportunities for having AutoCAD® Architecture generate a Structural Member Style automatically. When you need a Structural Member Style that has a single Structural Member Shape for both the start and end shapes, with no offsets, then you will want to take advantage of the automatic features. Even when you have a more complicated need, starting out by generating the style automatically may help save a few steps along the way. When the automatically generated styles will not meet your needs, you will need to either create a new style or edit a generated style. This article will take a look at some of the things you can do with manually created Structural Member Styles.

Structural Member Geometric References
Understanding how ACA labels the axes of a Structural Member is key to avoiding confusion when specifying the parameters we are about to examine. The diagram below shows the polyline from the High Detail shape for the W24x76 shape, inserted "as created" relative to the World UCS. The blue UCS Icon in the lower left corner shows the axes of the World UCS. For this shape, the insertion point was defined at the geometic midpoint of the shape. The X-axis of a Structural Member runs along the length of the member; the positive direction is from the starting point to the ending point. The Y-axis and the Z-axis are perpendicular to the X-axis. For a shape with no rotation, the positive Y-axis is the same as the World UCS positive X-axis of the shape and the positive Z-axis is the same as the World UCS positive Y-axis.
Confused? Keep the diagram above handy when editing the parameters of a Structural Member Style.

Another thing to keep in mind when setting up your Structural Member Style is that the final position of the shape(s) you define will depend upon the Justify property (found in the Dimensions category on the Design tab of the Properties palette) of the Structural Member. Baseline will place the insertion point of a shape at the starting point of the Structural Member, if no offsets have been applied to the shape. Middle Center will put the geometric midpoint of the shape(s) (with offsets, rotations and mirror applied, as applicable) at the starting point of the Structural Member, for the Medium Detail and High Detail geometry. Applying different offsets to the start and end shapes will also affect the calcuation of the geometric midpoint. Most Structural Member Styles will not need to be that complex; should you need to create one with that level of complexity, you will want to start as simply as possible, checking the effects of each edit before making the next one.

Automatic Structural Member Style
First, we will look at the automatically generated W24x76 Structural Member Style that was created in Part 1, to get an understanding of the inner workings. With a drawing open in which the W24x76 Structural Member Style has already been created, on the Manage ribbon tab, on the Style & Display panel, select the Style Manager tool to open the Style Manager dialog. In the left pane, expand the Architectural Objects and Structural Member Styles nodes and select the W24x76 style. [Make certain you are under the Structural Member Styles node, and not the Structural Member Shape Definitions node.]

The General tab of a Structural Member Style has the usual features found when editing other styles and definitions. You can edit the Name, provide a more detailed Description, add a Keynote, attach Notes and attach Property Sets. In addition, you can specify whether or not objects of this style can act as boundaries for associative Spaces. As you can see below, an automatically generated style only has the Name you specified at the time of generation; you will have to add the Description, Keynote, Notes and/or style-based Property Sets that you want.
The heavy lifting for a Structural Member Style takes place on the Design Rules tab.
The W24x76 shape has a single Component, called Section. Structural Member Styles can have multiple Components; the display system allows for display control over a maximum of ten. The Add, Copy and Remove buttons in the lower right side of the Design Rules tab allow you to add a Component, add a copy of an existing Component or remove an existing Component, respectively. You can give each Component a name of your choosing, which can help when editing the display properties at the style- or object-override levels. Each Component has two sets of parameters associated with it, one set for the Start Shape and one set for the End Shape. If you are not seeing these, then the button labeled Hide Details in the image above will read Show Details; click it to show the parameters.
• Name The name parameter specifies the Structural Member Shape Definition assigned to this component, selected from a drop-down list of the shapes defined in the current file.
Most times you will want to have all of the shapes you need defined before creating the Structural Member style. If the End Shape is to be the same as the Start Shape, and have the same Scale, Mirror, Rotation and X, Y and Z Offsets as the Start Shape, choose the same shape name, preceeded by an asterisk, from the End Shape Name drop-down. This will lock out those properties for the End Shape and assure that any changes made to the Start Shape will also be made to the End Shape. (This is the initial default when adding a new Component.) You can still specify the Relative to and Node parameters for the End Shape. If you want to use the same shape, but change anything other that Relative to and Node, choose the shape name without the initial asterisk from the End Shape Name drop-down list.
• Relative to The Start and End Shapes can be placed relative to either the very Start of the Structural Member or the very End of the Structural Member, by selecting either Start or End from a drop-down list. For an automatically generated, single-shape style, the style will be based on a single segment member, with the Start Shape set relative to the Start and the End Shape relative to the End.
• Node The Node parameter is an integer that indicates the Node number (relative to the Structural Member end specified in the Relative to parameter). A single-segment style has two Nodes, 0 and 1. Multiple-segment styles will always have one more Node than the number of segments. When Relative to is set to Start, the 0 Node is the first Node of the Structural Member, the 1 Node is the second Node, et cetera, with the highest number Node being the last Node. When Relative to is set to End, the numbering is reversed, with the last Node being the 0 Node, the second-to-last node being the 1 Node, et cetera, with the highest number Node being the first Node. That is why, in the W24x76 style, both the Start Shape and the End Shape are at Node 0. These are not the same Nodes, since the Relative to settings are Start and End, respectively.
• Scale You can apply a real-number scale factor to the shape, to uniformly increase or decrease the size of the shape from what is defined in the Structural Member Shape Defintion. This can allow a single definition to serve multiple sizes, when a single scale factor works for resizing the shape.
• Miror The Mirror parameter has a drop-down list with two choices, Yes or No. Yes will mirror the shape about the Z-axis of the Structural Member.
• Rotation The Rotation parameter takes a real-number angle value (in the drawing's current angle units), and rotates the shape about the shape's insertion point.
• X Offset The X Offset is a real number distance value (in the drawing's current linear units) and specifies an offset along the Structural Member's longitudinal axis from the Node at which the shape is placed. Positive values move the shape in the direction from the starting point toward the ending point.
• Y Offset The Y Offset is a real number distance value (in the drawing's current linear units) and specifies an offset along the Structural Member's Y-axis. (Refer to the first image above.)
• Z Offset The Z Offset is a real number distance value (in the drawing's current linear units) and specifies an offset along the Structural Member's Z-axis.
The final parameter of each Component is the Priority. You can ignore this for single-component styles or for single-segment (two nodes, 0 and 1) styles. Priority is used to control the mitering of components meeting at a common node. Components with the same priority will miter with each other, even if they do not intersect (provided there are no X offsets); components with different priorities will not. The Priority parameter can also be used to limit the justification of a structural member to just those components with the highest priority. This is done using the Justify components property on the Design tab of the Properties palette, found under the Basic category and Dimension sub-category. You can have the justification based on All components, or Highest priority only components.

Manual Structural Member Style Examples
The Start and End Shapes can be the same, as in the W24x76 style examined above, but they need not be. If different shapes are specified, ACA will transition from the Start Shape to the End Shape over the length of the component. For example, if the Start Shape is a 24x24 square and the End Shape is a 12" diameter circle, both with insertion points at the center of the shape, and added without any translations or rotations...
...you get something that looks like this.
Making a copy of the W24x76 Structural Member Style, changing the End Shape Name to W24x76 (without the asterisk) and applying a 90-degree rotation to just the End Shape...
...results in a Structural Member that does this.
In the W24x76 Double Structural Member Style shown below, I started out with a copy of the W24x76 Structural Member Style, selected the Section component and used the Copy button to create a copy of the Section component. I renamed the copied component to Section2 and then added Y Offsets of -9" to the Section component and 9" to the Section2 component.
This creates a double column.

Next Article in the Series (Structural Member Contextual Ribbon Tab)