• Registered: 2016-11-12
  • Posts: 3

Topic: Out-of-plane-bending

I am new to Amquake, I've just built my 1st model and have run all of the analyses, and have tried to make some sense of the results.

I cannot see anything relating to possible wall failure due to out-of-plane-bending, i.e. the masonry blocks "blowing out" from the wall in the direction of an earthquake.

Does anybody know how best to deal with this issue if it is not calculated within the program? Perhaps you may follow different documentation to calculate this?

Any advice from anybody would be most welcome.

  • Registered: 2010-12-08
  • Posts: 40

Re: Out-of-plane-bending

Hello,

i dont know your model, but for better understanding of the calculation you can open or create the model with only one wall and try calculate and post-process it.

Do you have set out of plane excentricity for the wall?

  • Registered: 2016-11-12
  • Posts: 3

Re: Out-of-plane-bending

I've actually done that, firstly with a 3.0 m long × 3.0 m high panel, and again with a 1.0 m long × 3.0 m high panel, to try and understand how the program works.

But I am not talking about any particular wall being "pushed over", I am talking about the blocks "blowing out" i.e. failure of a wall panel due to out-of-plane forces. I do hope that makes sense to you.

I can't see anything in either the input data, or the output data, that indicates that the program actually calculates out-of-plane bending, either capacity or demand.

What we are talking about here is really as if the blocks were "infill". If the surrounding concrete frame responds elastically and deflects very little due to in-plane forces, then in theory the confining reinforced concrete structural elements have to physically elongate for the blocks to fall out of the wall at 90°. So the failure mechanism could either be this happening, or the individual bonds between the blocks failing in out-of-plane shear.

If you imagine a stack of bricks which you can just push over. If you put a beam along the top which is properly restrained, you cannot push over the wall so easily. But the individual blocks could fall out of the wall when pushed. If you then apply vertical force, the wall becomes more resistant to out-of-plane forces due to frictional forces being generated between the blocks.

I'm assuming that when you do calculations for a structure in a high seismic area, the local authority would expect to see calculations (or otherwise) demonstrating that the walls will not fail in this manner. Since I am using Weinerberger Porotherm th+ 25 blocks (from France), this may be something that can only be determined by shake-table testing perhaps?

Any advice that you have on how you deal with this would be most welcome, assuming that the program does not take this failure mechanism into account.

  • Registered: 2010-06-28
  • Posts: 8

Re: Out-of-plane-bending

The failure you are describing can happen only if you apply horizontal pressure on the wall, i.e. for instance from earth or water or very strong wind. Such a failure will not typically occur in an earthquake unless there is something heavy next to the wall. For instance a heavy cupboard.

Anyway, this is a local failure of the wall, and such a failure is not considered in the AmQuake. AmQuake makes assessment of each wall against the general moments or shear forces, which can be both in plane or out of plane. So it can simulate an out-of-plane bending or shear failure coming from the inertia forces of the whole building, typically mainly from inertia forces due to the dead load of each storey.

I hope my explanation helps, with best regards

Jan

  • Registered: 2016-11-12
  • Posts: 3

Re: Out-of-plane-bending

Yes I do understand that. In this case we have an extremely high peak ground acceleration – 13.2 m/s/s for the elastic spectrum – and the worst forces would be seismic, generated by the weight of the clay blocks themselves. The failure mechanism would be arching within the boundary frame, or failure of the horizontal joints (unlikely) or the vertical joints (possible).

Obviously walls with openings would be the most vulnerable.

I just wanted to make sure that the program did not check this, and you have answered my question, so thank you. I can do some hand calculations to justify this.