I'm (still) working on analyzing my existing waffle slab. I've worked out a lot of the kinks, but the user shear bars are still throwing me for a loop.
I assign user shear bars adjacent to the column drop cap like so:
The result once they get detailed is this (top center in the picture), which is clearly not 8#3 bars in each rib:
And the analysis shows no appreciable increase in shear strength in the column strip with bars vs the adjacent spans without shear bars:
Any guidance would be welcome.
Thanks.
When trying to design a cross section that contains multiple shear cores for a single integrated section force, some "averaging" approximations must be made. For this reason, when designing cross sections with multiple cores RAM Concept only considers transverse reinforcement contained in the primary (largest) shear core and only allows one user transverse bar to be defined in this core. This is similar to how the program transverse reinforcement has always been detailed in RAM Concept. This reinforcement would then need to be distributed appropriately (proportionally) to any other cores in the cross section. It is also important to remember that longitudinal reinforcement requirements are also a part of the shear/torsion solution, so caution needs to be exercised not only when detailing the transverse bars but also the longitudinal bars for this case.
The best way to prevent having to deal with these detailing issues manually is to make sure that only one shear core is contained in each span segment strip. This eliminates the need for RAM Concept to make the approximations noted above during calculations. This could result in many more span segment strips to define, but should not be terribly time consuming or cumbersome otherwise.
Answer Verified By: TLiebhold
The 3D image was intended for illustration of the issue. Here's the error from the Calc Log:
WARNING: 37C-4 ((208.5,103.8)(223.5,103.8)) contains user transverse reinforcement but has multiple shear cores. Shear/torsion calculations may be approximate.
User Continued After Warning
WARNING: 37C-4 ((208.5,103.8)(223.5,103.8)) contains user transverse reinforcement that is not within the primary (largest) shear core. This transverse reinforcement will be ignored.
This says to me that because the shear bars were't in the drop cap, they were ignored. For a large slab like mine doing individual strips for each beam would be prohibitive.