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Flat plate punching shear

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Greetings,
 
I am currently designing Post tensioned concrete floor systems for multi-story mixed-use buildings. I am using RAM Concept for the PT design and I had a few questions pertaining to punching shear.
 
The program analyses the flat plate for punching shear and calculates a overstress ratio for the failed columns and gives the punching shear reactions and moments for the same. This is then supplied to a third-party program (Decon Studrail) to calculate the shear reinforcement required for punching.
 
1. Is there any rule of thumb to calculate/use for the bending stiffness factor for edge/corner columns, since you would expect them to crack and have a lesser resistance to rotation. I currently use 1.0 for all columns which is probably overconservative for edge columns.
 
2. Currently I am using the moments from the program to design the studrails. The moments, I presume, is used by the program to come up with the flexural reinforcement for the slab. In that case, is there a reduced value of moment that can be used to design for shear since only a part of it will contribute to shear, or is it conservative to design for the entire moment?
 
Thanks,
Anantha Narayan


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