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  1. Danielsp

    Changing structures over time

    Yes, rb... I did say it was a slab. In passing. But I wasn't discussing the slabs, even in that message. I mentioned it for the sole reason that... you asked me to! ("what are you building that you need to jump through these hoops ?" 4 Aug 22 16:58)
  2. Danielsp

    Changing structures over time

    Rb, yes... that's his last message. After he laid out the general concept and created a simple example. As I said, I was never talking specifically about slabs or a slab. The whole time I was asking about a general problem, but suddenly everybody else changed the subject. I guess that's because...
  3. Danielsp

    Changing structures over time

    Rb, the problem had already been fully understood and solved by steveh49 a couple of days ago. I didn't quite understand what was everybody else's goal on the topic after this. He answered my question, but I'd be glad to continue discussing the issue if that's what you'd like to do. As I stated...
  4. Danielsp

    Changing structures over time

    Folks, unfortunartely I'm not at liberty to release more detailed data. I was really just trying to discuss general principles, not one specific structure.
  5. Danielsp

    Changing structures over time

    The slab is actually a strut for the walls. The upper level of the new slab will be on top of the existing one. The lower, under it. The hole has around 240m² in a total of some 1000m². Outside the whole, the new slab is 2m thick.
  6. Danielsp

    Changing structures over time

    Tomfh, I'm worried about both. I'm chopping a third of the hole at a time. The hole is a rectangle of some 5,5x25,5m that starts at the perimeter and runs through the center. The existing slab is fully supported by the soil below. The walls are at the perimeter of the circle.
  7. Danielsp

    Changing structures over time

    Rb yes, that's a reasonable description. In that spirit, parts of the reinforcement would be on top of the existing slab and parts of the reinforcement will be under it. So, this is how it goes: 1) Existing slab is already loaded 2) Upper reinforcement is built 3) Part of the existing slab is...
  8. Danielsp

    Changing structures over time

    Drift, at least for me, solving the physical problem was not easy. So much so that I came here looking for answers, and even after some discussion, someone else solved it. Apparently, it wasn't easy for most people. To prevent the rotation of a structure node in real life and then build...
  9. Danielsp

    Changing structures over time

    rb, the slabs are not in different spans. On a vertical projection, they occupy the same area, a full circle. The final shape is partly above and partly below the existing one.
  10. Danielsp

    Changing structures over time

    drift, I guess steveh49 already solved the problem. I created an example based on his ideas at 4 Aug 22 11:50.
  11. Danielsp

    Changing structures over time

    rb, It's a 35m diameter 2m thick slab at the bottom of a subway access well 33m deep. There is already a 40cm slab in place but it's flat and part of final slab will be built below the existing slab and part over it (yeah, the 2m slab has a lower level some 2,5m below and it is connected to the...
  12. Danielsp

    Changing structures over time

    Drift, that would be easy to model. Just use a fixed instead of pinned support. But it would just be unfeasible to build.
  13. Danielsp

    Changing structures over time

    The building order and your account of my assumption are correct, drift.
  14. Danielsp

    Changing structures over time

    Brad, I didnt use a drawing because I was afraid it would tie the discussion to the specific case. The real situation I am analyzing, btw, looks very little like the one I showed. It is a slab, a hole of which will be demolished after other regions are reinforced. Actually, after the initial...
  15. Danielsp

    Changing structures over time

    rb, the 3,33 and 5,56 pic shows what WOULD be the bending moments IF the 10kN load had just added to the two left spans in the usual manner: no history, no previous deformations, no existing displacements or rotations, no initial 3rd span, only a plain 2-span problem. Just for the sake of...
  16. Danielsp

    Changing structures over time

    No, Brad. As I pointed out, you demolish after building. If it was the other way around, it would be trivial. And there is no rebuilding.
  17. Danielsp

    Changing structures over time

    Another way to do this would be to replace the right support by its force in the original structure, 0,93kN downwards, so it would look like this (spans are 3m wide each). But demolishing the right span amounts to the same as cutting the right support lose, so I add the necessary load to...
  18. Danielsp

    Changing structures over time

    A closer example to what I am doing is this. Suppose I wanna transform the first structure into the second while loaded 1) These would be the bending moments of the structures if built unloaded 2) So after loading the original structure, I build the new span and it looks like this (hinge...
  19. Danielsp

    Changing structures over time

    Steveh, if I get it right it's missing a final stage of removing something. In my case it's always adding and removing beams or plates, but I suppose supports work the same way.
  20. Danielsp

    Changing structures over time

    Not even real code, RB. A simple spreadsheet will do.

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