Spans Tab

Spans and Overhangs

The default length is 15'.  The default lenth of an added span is 15'

The default overhang is 4'.

To add a span or overhang, click the "plus" button for what you desire:

• + Add Left Overhang

  • This adds a Left overhang with a default length of 4'.  The button is changed to "Remove Left Overhang"

• + Add Span

  • This adds a 15' span to the current Member Span configuration

• + Add Right Overhang

  • This adds a Right overhang with a default length of 4'.  The button is changed to "Remove Right Overhang"

To delete a span or overhang

• - Delete Span

  • This deletes the right most span and automatically adjusts the Overall span dimension

• - Remove Left Overhang

  • This removes the Left Overhang, the Overall member length is recalculated

• - Remove Right Overhang

  • This removes the Right Overhang, the Overall member length is recalculated

Supports

Select "Flush" or "Bottom" for I-joist or beam designs. A Flush support indicates that a hanger is required. The type of support may also affect the floor performance rating.

Dimensions

Use the boxes below Supports and above Dimension Lines to enter in your desired dimensions.  You may enter the dimension in a number of ways. For example, if you would like to enter a dimension of 20'-6.0", you may key in

• 20'-6.0"

• 20'6.0"

• 20'6"

• 20'6

• 20.5

• 20-6

• 20 6

• 19 18

• 20.25 3

• 246

Regardless of how you enter it, upon leaving this field, it will be displayed as 20'- 6.0". 

Note the position of the extension line on the dimension string. This indicates the length of the design span, upon which the analysis is based. For flush supports, the end of the design span is typically assumed to be the physical end of the member, which is conservative. For bottom supports, the design span extends to the center of the required bearing length. The required bearing length, however, cannot be determined until the member design is complete. It is common practice to estimate the design span based on an assumed bearing length. Typical assumptions are that the design span terminates 1" beyond the inside face of bearing for I-joist designs and 1" for beam designs. At continuous supports, the design span is assumed to terminate at the center of the support.

Open-web design requires a clear-span dimension, which is to the inside face of bearing.

Member Slope

Lateral Support (in)

For open-web trusses, continuous top-chord support is assumed, and the bottom-chord option is disabled. Open-web trusses must be installed with lateral support as specified by RedBuilt™ engineering.

For beams, the defaults for lateral support are "Continuous" for the top edge and bottom edge. Typically the top edge has continuous lateral support from sheathing. The bottom edge may have continuous lateral support from a direct-applied ceiling or other means.

Lateral support of the bottom edge is required only where the bottom edge is in compression. The compression zone (for the bottom edge) can be determined from the moment diagram. It is the extent of the moment diagram that is below the horizontal line. The moment diagram can be scaled from the RedSpec™ graphics to determine the length of the compression zone. If the beam design fails in "negative moment," a long unbraced length along the bottom edge may be the culprit.

Lateral support of the bottom edge can be accomplished by installing blocking, bridging, gypsum, or 1x4 strapping. The strapping runs perpendicular to the joists, and is attached to the bottom flange and a braced end wall.

See Lateral Support for more information.