Eurocode 2 - Punching Shear due to eccentricity

[willowman]

Hi all,

I am having a little difficulty understanding the Eurocode 2 method for accounting for moment transfer at columns when assessing punching shear.

Referring to the EN1992-1-1 Designer's Guide, we see that β is the multiplier which is used to account for moment transfer.

My confusion lies with the following statement, 'the moment transferred is not the moment in the slab but rather the difference in moment between one side of the column and the other'.

If I consider a typical braced concrete frame, an edge column which has unequal adjacent slab spans would develop a bending moment diagram (about an axis perpendicular to the edge) as below due to gravity loads. My question is, shall the 'moment transfer' mentioned above be calculated as the difference between the two moments M₁ and M₂? It makes sense to me that this is the quantity of 'moment' which is transferred at the slab interface i.e. we must travel (M₁ + M₂) worth of moment to move from one face of the column to the other. Would this understanding be correct?

Evidently M₁ and M₂ will be of opposite sign and this suggests to me that the transferred moment (which we use to calculate β) is always positive?

If anyone could provide clarity it would be appreciated.

Thanks in advance,

 

[rapt]

You are trying to over think it.

Those are the column moments. If they are equal deltaM will be 2 * M1.

I cannot believe anyone would think the result could possibly be negative.

What the comment in the code is talking about is the slab moment either side of the column connection.

For an interior column, the column moment would be the difference in the slab moments either side.

For an end column, it is the slab moment.