| Product(s): | RAM Structural System; Ram Steel; Ram Modeler | ||
| Version(s): | 13.00.00.00 or later | ||
| Environment: | N/A | ||
| Area: | Analysis; Modeling |
Framing Tables Errors
General
There are many instances where modeling errors in Ram Structural System are not caught by Integrity - DataCheck in Ram Modeler. DataCheck looks at general geometric information, but it does not attempt to validate all of the information needed to determine the tributary loads to every beam and wall, what we call the Ram Gravity Framing Tables.
Many of these errors are slab edge or slab opening related. When one way decking is modeled, slab edges and slab openings must be associated with adjacent beams/walls. For this reason, avoid using free formed slab edges/openings with one way decking. Instead, use Layout - Slab - Slab Edge - Whole Perimeter and Layout - Slab - Slab Opening - In Bay to model the slab edges and slab openings. Then, revise the slab edges/openings where the offset changes. To further ensure accuracy, only use beams and walls in your Options - Set Snap Points. Finally, use a positive, non-zero, slab edge offset. Zero inch slab edge offsets are permitted, but the program algorithms were originally developed assuming non-zero offsets and some configurations can be problematic.
Below are several common modeling configurations that cause problems for the program but are not caught by Data Check. The right hand image shows the typical error message produced while building the framing tables. In the background, the framing tables usually halt at a particular member on a particular floor as shown in the left hand image. Typically, but not always, the modeling issue occurs in the vicinity of the member where the framing tables halt.
Illegal Framing Configuration
Most illegal configuration errors are slab edge or slab opening related. Subtle inaccuracies in member end locations can cause small slab edge segments that are problematic for the framing tables. Review the member end coordinates using the Layout - Beam - Show command and the slab edge coordinates using Layout - Slab Edge - Show. Try remodeling the slab edge using the whole perimeter command.
Starting with version 14.07, this error dialog more often than not references an invalid beam number, "Illegal Framing Configuration Detected on Beam -1.", but the number listed in the background framing tables dialog is still accurate and can guide you to a point near the problem. This error is typically associated with columns under a one-way deck that have no beams framing into them. Adding beams parallel to the deck span from the column to the adjacent framing should prevent the error from occurring.
If you get an Illegal Faming Configuration or Missing Slab Edge Detected error try using Slab Edge > Move to move each end of the slab edge along coordinates shown in the message. Use the snaps to move the edge and snap back to a column or beam that occurs at the end of the slab edge.
Missing Slab Edge
Many missing slab edge errors are related to having portions of the structure isolated from the perimeter beam loop under one way decking as shown below. To resolve the issue, model two beams that connect the isolated structure back to the adjacent framing. If these beams are modeled parallel to the deck span, they will take no tributary load from decking.
Internal Error in AdvanceNodeList()
Typically, these errors are similar to the missing slab edge error. The main difference is that there usually is only a single beam/wall connecting the interior structure to the perimeter beam loop as shown below. Modeling a second beam will resolve the issue.
Another common situation is where there is a complete set of steel framing and just beyond this a perimeter wall where there is a continuous gap between the two systems. As noted above, adding a few connecting beams between the outer columns and walls is sufficient to fix the AdvanceNodeList problem.
Beam Loop Intersection not Found
Typically, beam loop intersection errors are related to line loads that are slightly askew from a beam or wall. Often discrepancies arise when a single line load is added over multiple beams that are not truly collinear. Review the coordinates of the beam and line load using the Layout - Beam - Show and Layout - Load - Line Load - Show command. To resolve the issue, delete the line load(s) and remodel them using the Add On Beam command.
This error can also be associated with changes in one way deck orientation or properties. One way decking should always transition along a beam/wall. That includes transitions from one way decking to two way decking.
Furthermore, one way deck angles are normally limited to angles between 0 and 179.99 degrees. If imported models have deck angles larger than 180 degrees, this can also cause a beam loop error.
Failed to Find Slab Edge Loads
These errors are usually related to tolerance problems between the slab edge loop and perimeter beam loop. Review the slab edge and beam coordinates using the Layout - Slab - Slab Edge - Show and Layout - Beam - Show command. Try remodeling the slab edge using the whole perimeter command.
Failed to Create Slab Edge Load Polygons
This error tends to happen when there is a small level with an incomplete perimeter of framing similar to the one pictured below. Adding the short beam on Gird B between the two concrete columns completes the loop with beams 40, 39 and 41. Adding the other beams would only be required if the deck was intended to load beam 42.
For more information on this issue see Failed to Create Slab Edge load Polygons
Crash with no warning or error message
If a model crashes with no warning or error message then it is harder to diagnose the problem (especially if the Integrity - Data Check offers no clues)
One specific situation that can cause a crash is when a braced frame on an upper level is supported on a two-way deck with no supporting transfer beam. Where it's impractical to add a supporting beam, a work-around for this situation is to model the braces using the Add Standard - Knee brace approach using a vertical offset just a little less than the story height. When the braces intercept the column above the two-way transfer level the framing tables work properly without crashing the analysis and this should have minimal effect on the stiffness matrix.
Two Beams Overlap
Under normal modeling circumstances it should not be possible to model two beams that overlap or cross, but it can happen in some models particularly where the geometry is imported (from dxf, Revit or ISM).
It's difficult to visually identify where two collinear beams overlap for part or all of the length. Turning on the display of beam numbers can sometimes help. We have seen cases where one simple span beam and one cantilever beam are in the same location and two numbers will be shown rather than one.
Since the data check does not identify such a problem it only appears when running the framing tables. The error message does not indicate exactly where the problem occurs, but you can usually tell the level with a problem by the status of the framing tables just before the error occurs.
Finding the beams with the problem usually requires a trial and error process, deleting framing gradually until it works. Then going back and examining those beams that were deleted last in the backup more closely, moving them as required.
We have also seen cases associated with problematic slab opening edges. Deleting and carefully remodeling the slab opening edges at the beam identified where the framing tables stop resolved the problem.
Forcing a "Reframe" (aka Reset Status)
In some cases the beam design module can open and not require a rebuilding of the framing tables, what is commonly referred to as a "reframe". A reframe is generally triggered by making any kind of change on a particular level or it can be initiated using RAM Manager - File - Reset Status.
If the design module produces an unexpected error, one simple thing to try is forcing a reframe. You should get a window like this if previous results are going to be discarded:
This is nothing to worry about, it just means that the program will recalculate the tributary resutls from scratch.