What is the minimum edge slab thickness consitute a spandrel beam

[bratty]

To resolve punching shear at the edge of the flat slab with the exterior column, one way is to increase its thickness to form a beam. What is the minimum thickness to be considered as a beam especially to be used in PT slab

 

[KootK]

If the "beam" can deal with incoming shear, then it's deep enough for strength design purposes.

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[bratty]

Thanks for the answer.

 

[KootK]

You're welcome. Twice the slab depth might be a good starting point but isn't a hard rule etc.

Is the PT coming into the slab edge at this location banded or distributed?

HELP! I'd like your help with a thread that I was forced to move to the business issues section where it will surely be seen by next to nobody that matters to me:

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[rapt]

Seeing it is in Australia, hopefully it is neither banded or distributed but a proper 2 way tendon layout with column and middle strips if it is a flat slab.

A spandrel beam referred to in section 9 of AS3600 for punching shear should be stiff enough to create one way action along that edge and be able to carry the full load attracted by it in both flexure and shear. It is not a slab thickening such as a wide band beam which would normally extend a long way past the face of the column and itself probably require a punching shear check based on its depth.

 

[bratty]

Rapt

Thanks for your response. It is a 2 way flat slab. But to convert the end span from 2 way slab to one way slab, is to introduce a spandrel beam. Unless one uses a Adapt, RAM program or ENGINEERING software, is there any other way to determine or estimate the depth of the spandrel beam to ensure the beam is picking up the loads and then transfer to the column as beam shear.
An indirect is to work backwards and determine the shear capacity of the beam is greater than the actions from one way slab. But by hand calcs, is there a way to find if the spandrel beam is stiff enough

 

[rapt]

Bratty,

I would think that as long as the T-beam carrying the half span load was ok for shear, flexure and deflections it would be considered a spandrel beam.

 

[bratty]

Rapt

If the spandrel beam depth is still shallow ie not stiff enough, it will not attract sufficient load to act as a beam. See near the edge, there are set down for balconies. In the set down, the slab is thickened like a band beam. Will the thickening sufficiently constitute a beam to attract 70 to 80% of the one way slab load?

 

[KootK]

- in my opinion, providing adequate stiffness for one way distribution is a serviceability issue, not a strength issue. And for this, you need some means of assessing beam deflection, by hand or via automated tools.

- For strength, I feel that you simply need to provide a beam that is deep enough to get you enough shear capacity. In this application, the beam is functioning much like a shear head. And shear heads are thinner than their slabs.

- Like rapt said, your beam either needs to be close in width to the column width or it needs to have a wide beam / punching check of its own.

I'd start by assuming one way distribution, designing a beam that can resist the shear , and then seeing where you standu

HELP! I'd like your help with a thread that I was forced to move to the business issues section where it will surely be seen by next to nobody that matters to me:

http://www.eng-tips.com/viewthread.cfm?qid=456235