I have a 9" conventionally reinforced, 2-way slab that I am running in RAM Concept and I am running into a problem when I start to specify user reinforcement in some areas.
As you can see here, I have run the model and everything checks out fine. I have a full top and bottom mat and additional program reinforcing is being shown at the top mat:
Now on this support location of interest all I did was change the 19#6 bars from program to user reinforcement, and all of a sudden the strips are failing per 10.3.5 and a ridiculous amount of bottom bars are provided:
Any idea what could be causing this? I have this happening at several other locations with no particular rhyme or reason.
Your model contains continuous layers of top and bottom reinforcement. Reinforcement cut-off along the spans does not appear to be a concern. For this reason, I recommend changing CS (and MS Span Detailer) to "None." This will remove a lot of the added program rebar from the model.
In some of the design strips, a small portion of the drop panels extends into the middle strip. This results in a small shear core and shear failures. To avoid these failures, I recommend editing the span segments in each direction, unchecking the box for "Middle Strip Uses Column Strip Properties" in the Middle Strip tab and using "Slab Rectangle" for the trimming option. You will need to change the bar and cover properties to match the column strip. Remember to change MS Span Detailer to "None" per the discussion above.
Please post back if you have any other questions.
I would be very careful about disabling the span detailing setting for two-way slabs with drop panels. When span detailing is disabled, RAM Concept will not run Pass 0 which excludes the user reinforcement from the calculation. Instead, Concept will consider ALL user reinforcement when performing the analysis, including the bottom mat. When span detailing is disabled, the bottom reinforcement will contribute to the negative bending strength in the drop panel. Depending on the depth of the drop panel, the bottom mat can provide a significant contribution. In my opinion, it is inappropriate to use the bottom steel for negative bending checks.
As far as I can tell, the only way to avoid contributions from the user bottom steel is to turn span detailing on and allow Pass 0 to calculate the top steel while ignoring all user steel. This is one reason why the required top steel is often much larger when span detailing is turned on. In my opinion, the larger required quantity is justified, and while technically you could consider the contribution of the bottom steel toward the negative bending strength (provided it is detailed with the appropriate continuity), this is not how two-way slabs are traditionally designed and detailed.
This process is not obvious to the user in either the manual or the output, but it is important to understand the implications. I am not aware of any other workaround to solve this issue. I would love to hear what RAM/Bentley suggests for these situations.