Connection's PT Slabs 2

[structbureau]

Hey,

I am having an issue with typical temporary movement joint detailing using horizontal dowel's grouted after 56 days in my PT-flat plate slab.

The situation:

I am trying to isolate lift/stair well core walls and a shear wall using horizontal dowel connections. They are located 35 m away from each other however the shear wall runs perpendicular to the core's.

The builder and consultant want to use 170mm slabs with 8.3m spans (however not allowed by current codes but they have a tech gliche in there DA) so P/A is quite high to control deflections etc varying b/w 2-2.5 P/A....

The rest of the perimeter is isolated by a building movement Joint...

The question:

In theory the TMJ detail works, however how do you ensure that onsite workers install the horizontal dowel joint system properly and centre the reinforced bars to the PVC piping provided?

.. i.e. normally they will just sit the PVC piping on the bars and it would not be central (gravity). I wouldn't worry about this normally but because of the high P/A shortening of the slab will be quite significant, 170mm deep flat plate will crack quite easily when restrained.

I'd like to hear your technique / system you use for correct installation..

Regards
Bill Mason

 

[hokie66]

Not sure about the details of your proposed system, but the high PT will still only be a relatively minor part of the volume change. Shrinkage is normally about 60-70%. The only way you can ensure that a critical field activity will be done correctly is to inspect it yourself, which will require a significant amount of time on site. And I do agree that 8.3 metres is a long way for a 170 flat plate. Are your punching shears OK? If the builder has that much control over the design, good luck with the 56 day delay.

 

[structbureau]

Sorry maybe I was giving to much info..

Simply,

I am using a horizontal dowel connection to transfer the shear from the slab into the support in this instance the core's.

The dowel connection is for example a N16 bar with a PVC duct placed over the bar to allow for temporary movement and after 56 days we can come back and grout through tubing and lock it in. (this is a typical PT detail & doesn't halt construction of the project, and would only be MAX 20 bars)

What techniques / procedure can I use to maintain that the bar will stay central to the duct...??


.. Punching is looked after what they are saving in concrete they will be blowing out in stud rails however they have height issues with the floor below.

 

[dik]

You'll find long spans with shallow HC members have an upward camber that will increase over time... have often used 8" for 32' spans, for apartments... they creep upwards.

For post-tensioning work, I"ve often added a short polyurethane 'pipe insul' sleeve to provide a movement space.

Dik

 

[hokie66]

My advice won't help, as I am prejudiced against dowels for shear transfer, bouncy slabs, and studrails.

 

[rapt]

Agreed Hokie,

Stud rails (or any type of punching shear reinforcement) in a 170mm slab! No way.

L/D of 49 with precast, so limited continuity! No way. Who cares if they creep upwards, they still bounce.

Maybe the carpets and floor coverings will stiffen it all up and suupport it all!

 

[hokie66]

Not sure where the precast idea came from. The OP's slab is cast in place, I think.

 

[rapt]

Hokie,

dik was talking about HC which I assume is hollow core precast!

 

[hokie66]

I see. Dik changed the subject. The OP wasn't asking about precast.

 

[dik]

Not quite in line... but with the long span and shallow depth... I was pointing out that upward camber may be an issue...

Dik