RAM Concept Conflicting Audit Strip Results

I have modeled a 1-way PT slab and beam system starting with RSS and importing into Concept. At the lowest level I have several columns that need to jog. The audits on the strips at those locations produce a couple sections with errors that suggest removing 100% of the PT but adjacent sections may tell me to increase the amount of PT by a more reasonable percent. 

Is that a function of the forces induced by the column jog, or am I missing something? 

I have uploaded my file with the post URL. When opening uncheck all of the import options from RSS as I have made some geometry and load modifications to the model that would be overwritten. 

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  • I have your file but I'm not sure what strip you are inquiring about. I think I can answer in general terms, however. 

    The program is evaluating the strip stresses and also a balanced load percentages. For details on how this is done, see the program manual, section 54.8.5 "Calculating the balanced load percentages" and chapter 34, "Using the Auditor".

    In the audit, if the section fails then it will make a suggestion. Here are some details form the manual on that: 

    For an unusual span definition or PT layouts I think you will want to treat the balanced load percentages and the audit suggestions with a grain of salt. Review the stress diagrams, as well as the deflection (e.g. due to the All Dead + Balanced condition) to double-check for over or under balancing and make a judgment call. It may very well be that you need to adjust the tendon drape, or the design strip layout, rather than the number of strands. 



    Answer Verified By: Max Karr 

  • One more follow up on balancing; over on the right side of the building at where 24C-2 and 25C-1 diverge. Our intention for the forked beams is really to detail that entire wedge as one wide beam as opposed to a forked beam. Since I set this model up in RSS there is an obvious modeling issue here as in the case of this one way slab system I can't have unsupported slab edges. 

    Currently the beam with section 25C-1 has a DL balance of -520% which creates some PT drape issues. While the 24C line has realistic balance values. I can determine that the program doesn't consider 25C as a part of 24C.

    So my questions are:

    Should I keep this forked beam system that I have, or should I delete the beams out and model a thick slab in concept to analyze more closely to how we intend to build it? 

    If keeping the beam system, is there a better way to define the design spans such that the program understands the intention?

    If changing to the thickened slab approach would that cause some confusion when exporting back to RSS?

Reply
  • One more follow up on balancing; over on the right side of the building at where 24C-2 and 25C-1 diverge. Our intention for the forked beams is really to detail that entire wedge as one wide beam as opposed to a forked beam. Since I set this model up in RSS there is an obvious modeling issue here as in the case of this one way slab system I can't have unsupported slab edges. 

    Currently the beam with section 25C-1 has a DL balance of -520% which creates some PT drape issues. While the 24C line has realistic balance values. I can determine that the program doesn't consider 25C as a part of 24C.

    So my questions are:

    Should I keep this forked beam system that I have, or should I delete the beams out and model a thick slab in concept to analyze more closely to how we intend to build it? 

    If keeping the beam system, is there a better way to define the design spans such that the program understands the intention?

    If changing to the thickened slab approach would that cause some confusion when exporting back to RSS?

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  • As for beam modeling, you can make adjustments in Ram Concept - Mesh Input - Standard Plan, just remember not to reimport the beams and slabs again after that. It the analytical behavior is affected by modeling it more exactly, then this work is worth doing. If nothing else, the "no torsion beam" behavior ought to be avoided for forking beams (your model already has this correct).

    As for design strips, you can have a segmented span segments (partial length design strips) if needed where part of the span is wide, and then later splits into two parts. Where there are angled beams coming together it can get messy, due to span boundary limits from adjacent strips, so one other strategy is to use individual design sections at key locations.