Increase stiffness modified PT transfer plate 2

[KAR FUNG]

Hi All,

I plan to increase stiffness modified PT transfer plate (PT thick slab support 35 typical floors above)from 0.25 to 1 or more than 1. Any suggestion than I can increase the stiffness modified PT transfer plate.

Thanks

 

[KootK]

I'd cerainly support an icrease above 0.25 if a detailed analysis indicates limited serviceability cracking as I'd expect. It's not clear to me how you'd justify avalue greater than one tbough unless you'rre somehow trying to account for load balancing effects via stiffness modifiers which is a trick I've not yet seen.

One wants a transfer slab supporting 30 stories to be nice and stiff.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[rapt]

Yes, you should calculate the real stiffness under the loading condition being analysed for. So if you are looking at ultimate strength, or worse earthquake action, you need to calculate the stiffness under that loading condition, not your basically un-cracked service condition. And the stiffness will vary in different areas of the slab. The "column strip" which gives you most of your sway stiffness will be a lot more cracked than the middle strip, or the ACI average value. That has to be accounted for.

Not sure how it can possibly be greater than 1.