VisualAnalysis assumes that the length of a member element is equal to the unbraced length. It is up to you when you create a design group, to specify the actual unbraced length for members in the group. This is one of the key criteria that you will use in determining which members to group together.  Bracing is not automatic in VisualAnalysis, you must pay attention to this important detail.  The terms top and bottom relate to the member's section axes, and may not refer to the actual 'top' of the member! 

Graphics

To see the location of bracing on a member use the Brace Locations checkbox found in the Member Details section in the Filter tab while in the Design View. 

Three Directions to Brace:

1. Lateral Top (+y): at the +y face of the member, for strong flexure checks
2. Lateral Bottom (-y): at the -y face of the member, for strong flexure checks
3. Strong (z): for axial compression checks
4. Torsional (x): for twist in each of the above directions (steel only) other assume Minimum(KLz, KLy) as needed.

Ways to Specify Brace Positions

These are brace locations along the length of each member element.

• Unbraced
• Bracing Patterns (e.g. midpoint, third point)
• Bracing Fractions
• Specified Unbraced Length
• At Interior Crossings (for members with intermediate connections)

Bracing Patterns

By default, each member element is braced at its end points and unbraced along its length.  Bracing patterns allow you to define intermediate bracing points that are not part of the VisualAnalysis model. 

You may specify a bracing pattern like continuous, mid-point, third-point, or quarter-point. This means that for each member element, a brace is assumed to restrain the member against buckling at these specific positions along the member. This is a fast and easy way to specify the bracing and it can work well even if the members are of different lengths. You may also restore members to the default unbraced state using patterned bracing.

Bracing Fractions

By default, each member element is braced at its end points and unbraced along its length.  You may use fractional bracing to define the locations of intermediate brace points along members.

Fractional bracing is similar to Bracing Patterns but allows an essentially unlimited number of patterns. You simply specify that braces exist at specific fractions of the member element length. These fractions are defined from the start-end of the member element.  You create a list of fractions to locate braces at arbitrary positions along each member element.

This method also works if member elements have differing lengths. Fractions should be listed in increasing order in the range of zero to one. For example, "0.5, 0.625, 0.79"

Specified Unbraced Length

When you specify a specific unbraced lengths, these braces are assumed to exist at fixed distances from the 'start' end of the member element until the end of the member is reached. You may specify an unbraced length that is longer than the member-element length to model things like a chain elements that is not exactly straight and where VisualAnalysis will not allow a 'Combined Member'

Using the specified unbraced length can result in an incorrect calculation for the Cb value and other possible errors in checks--please use wisely.

At Interior Crossings

VisualAnalysis provides a convenience feature that lets you combine member elements into a single composite member for design or reports.  Behind the scenes the member consists of multiple elements with interior node points.  The design software does not automatically "see" the interior node points as braced points, but you may specify this option in the bracing.