Can we say that punching shear behaviour in flat slab and raft/pad is the ‘same’?
Consider the two models to compare by using 700mm thick flat slab and raft/pad. Should both flat slab and raft/pad require the same thickness for punching shear to pass? Or raft/pad will require more thickness, say 950-1050mm.
I was thinking it won’t be the same because of the moment in raft/pad compared to flat slab.
TQ for the answers.
Additional info: Assume both are of the same materials.
1) In flat slab, apply area load to the slab to give some reaction to the column supporting the slab which will punch through the slab.
2) In raft/pad, apply the same column load.
Need more information:
Are they the same material? How is the punching load being applied? How are they supported?
Sorry, still unsure of the question here. Is the “raft” meaning a footing that the column sits on – meaning you’ve got a column supporting the slab, and the raft/pad supports the column?
Resistance to punching shear is the shear resistance of the plane of failure – the thickness times the perimeter of the area “punched”. This is generally taken as a perimeter the same shape as the column that transfers the load, but a distance equal to the slab thickness away from the face of the column.
If the total load is the same, and the area its applied on is the same, then the thickness will be the same. Punching shear isn’t related to applied moment.
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