Prying in baseplates

[rowingengineer]

Prying in base plates or similar connections in my opinion shouldn't be taken into account due to a few reasons

1. Concrete is softer than steel such that under loads crushing/squashing of the concrete will occur

2. Most design books use thick type plate design such that the bolts will extend to such an extent being normally only lower grade that the steel can't deflect and apply the load.

3. on steel connections you have two plate yielding and prying occurring, in a steel to concrete connection only one side of the connection is able to apply the force if it were present.

When in doubt, just take the next small step.

 

[BAretired]

1. Concrete is certainly softer than steel, but it is usually capable of resisting prying forces without crushing or squashing. That is because the steel plate is bending, so the relative hardness of the two materials has little to do with the issue. For flexible base plates, prying action should be considered.

2. If the plate is rigid enough, prying action may be ignored.

BA

 

[JoshPlumSE]

In response to your arguments:

1) A 0.75" thick baseplate that cantilevers out from the column is stiffer than a 4 ft thick block of concrete? I don't agree with that.

2) This I do agree with. Most of the time you will be using a baseplate that is thick enough that if you were to do the prying calculations then they would not be all that significant.

3) This argument and item #1 are in nearly direct contradiction to each other.


I don't think that it is common practice to include prying effects in baseplate design. However, some years ago I put together some spreadsheet to do this for both baseplates and bolted end plate moment connections.

Based on that experience, I would say that it can legitimately have an effect on anchor bolt forces. But, it wasn't such a large amount that I was very concerned about it for the types of connections we were designing.

Josh

 

[phuduhudu]

I too have recently done the baseplate prying checks and have ended up with about a 10% reduction in tensile capacity for the connection due to prying. In fact I sized the baseplate to get it down to the minimum 10% prying force.