Slab Bands 3

[slickdeals]

I know this item has been discussed before in this forum, but I wanted to ask a few more questions (specifically with how Ram Concept analyzes it).

I have a grid of 11m x 8m with some really heavy loads. I am using a 300mm thick slab with a 500mm x 2700mm slab band (in the 11m direction).

According to PTI and Bijan Aalami's recommendations, as long as the thickness of the band is <= 2t and width >= 3*overall thickness of band, then the behavior generally remains two way.

My question pertains to the design strip in the 11m direction. Ram Concept has the option of choosing either full width or Code T-beam for these strips.

For one way shear checks, the program is using only the width of the 2.7m wide band. Is this appropriate or should the one way shear check be based on a 8m wide strip?

For flexure checks, I think (conservatively) the band beam should be analyzed as a T-Beam and not a two-way slab.

Any other thoughts/suggestions are welcome.

 

[slickdeals]

Can I perform a strain compatibility analysis with composite metal deck and post-tensioning (bonded in grouted sleeves)? In that case, can I assume the metal deck similar to reinforcing at the appropriate "depth" and then check the shear flow VQ/I to ensure adequate bond to the deck?

 

[slickdeals]

Since this is a new system to me, are there any references/literature to verify my analysis? Do the Aussie prestressing companies use the BONDEK as bottom reinforcing and perform strain compatibility analyses?

 

[rapt]

slickdeals,

Yes, but the bond properties of deck vary significantly. Some decks have very poor bond and cannot be used in this way. Others are designed to provide relatively good bond with special embossments etc and can be used this way. You need to test the deck. And you need to allow for the developemnt length which is dependent on the bond properties of the deck and much longer than for normal reinforcing. So you cannot just assume normal reinforcing properties.

Eurocodes have a code on this, EN1994-1-1, chapter 6 I think.

RAPT software includes this design procedure. It can be used for any deck type as long as you have test data for that deck type to define the bond properties.

Unless you have very high live loads, decking is normally of no benifit with PT as you already have sufficient +ve moment capacity from the PT. Decking actually hurts as it increases your deflections due to shrinkage restraint effects.

 

[hokie66]

A word of caution...when using deck as reinforcement, consider exposure conditions, both for corrosion and fire rating.