Effective shear width for concentrated load near simple support

I would go with punching check.. As far as i know, EC-2 and ACI-318 are silent for this case. The following excerpt is from FIB MODEL CODE 2010 if you feel more detailed check is necessary..

I've been using the Dutch method under the impression that is still the state of the art.

In practice, most slabs wind up being clamped to some degree so the methods converge in that sense.

OP said:

The Australian codes are relatively silent on it

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AS3600 Clause 9.7 has the formula for load resisting width for concentrated loads, which results in a value similar to 45 degrees.

Tomfh, that clause relates to a 'moment resisting' width specifically.



Maybe it makes sense to apply it to shear strength also.

However, when I take that clause at face value, I interpret it to give the following effective width, which has a parabolic shape, not linear. And the effective width at the support (where a = 0) is equal to the width of the load patch:



What I, and I assume many others, have in mind is a constant-width strip, with the width determined using 'a' at the position of the load patch. Possibly this is what the clause intends to do, but it is not worded that way. If this is the case, it should define 'a' as: perpendicular distance from the nearer support to the concentrated load.

The intention of AS3600 is a fixed width strip (beff) defined by the distance between the load and the support. The further your load is from the support, the wider the effective strip. Your plot is not a plot of the effective strip width at different positions along the slab, but instead shows how effective width changes as the load position changes.




The commentary says to design for shear over this effective strip width too, which gives values close to 45 degrees as you move towards the supports.

Thanks for clarifying, I suspected that was the case

It seems that the AS 3600 approach is a bit more conservative than the MC 2010 approach then