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Generating Span Segments [FAQ]

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Revision 1 posted to Structural Analysis and Design - Wiki by Seth Guthrie on 1/9/2015 7:52:16 PM

  
 Applies To 
  
 Product(s):RAM Concept
 Version(s):Any
 Environment: N/A
 Area: Modeling
 Original Author:Bentley Technical Support Group
  

 

When I click the generate spans tool nothing happen, why? 

The General Spans tool tries to connect the supports together with span segments.

Clicking the tool triggers the Generate Spans dialog with various options.

The first thing to check is that the Spans to Generate and the Orientation are correct for the span segments you are trying to generate. The image above if for Latitude span segments that span left-right on screen, connecting supports that are no more than 20 degrees from horizontal.

If the settings are correct, but no spans are generated, it could be because the program is ignoring the supports. The program logic for Elevated Slabs is to connect the supports below with span segments, and for Mat footings to connect only the supports above. "Supports" here include columns, walls, point supports and point springs, but not area or line springs, line supports nor beams. The programs determines if the model is a Mat based on presence of area springs in the meshed model. When the model includes any area springs, then the whole model is treated as a mat footing in this regard. Otherwise it's an elevated slab and only supports below matter.

For hybrid cases like a mat on piles where the piles are supports below and a soil spring has also been modeled, the user may temporarily remove the spring, generate the spans, then replace the area spring and re-mesh, or just draw the span segments manually. 

Why do I get a warning every time span segments are generated?

Since the program is applying fairly simplistic geometric rules to the generation of span segments and not using any real intelligence in their placement, the program always reminds the user to adjust the span segments as they see fit.

Any strips that are not desirable can be stretched, moved, or deleted and replaced manually.

How does the program automatically determine the support width?

For design strips that end at columns, the program sets the support width to the column dimension plus a tiny amount so that the first cross section of the span segment is just outside the face of the column. Note, the support width in this case is based on the column overall dimension. The placements of the first section is at a location that is 1/2 of the support width away from the span segment end point. 

Consequently, if the span segment does not terminate at the column center, this 1/2 width approach will not work properly.

For wall supports, it's the wall thickness used.

When supports are skewed relative to the span segment some adjustments are made.

For circular columns the program uses 88% of the diameter.

The program does not automatically detect beams as supports. Thus, for strips drawn from beam to beam stopping at the supporting beam center line, the user should manually enter the support width based on the supporting beam width, plus some small amount.

What are the properties for generated span segments?

Double click the span segment tool (or the span segment polyline tool) on the right tool bar on either design strip layer.

Set the properties as desired, at least for the bulk of the spans about to be generated. Pay attention to the General property - "Consider as PT" in particular since the program default is for this to be checked. These settings will then be used for the generated strips. If span segments were already generated with the wrong properties, they can be generated again, or the properties for the span segments can just be edited by selecting them (together or individually) and using Edit - Selection Properties.

See Also

RAM Concept Design Strips TN

Structural Product TechNotes And FAQs

Tags: support width, Design strips, RAM Concept, Span Segments, Modeling, SELECTsupport

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