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  1. BeFEA

    A scaled finite element model

    Thank you for your answers. I don't know why, but think I had never heard of the Buckingham's Pi Theorem. I didn't go through it in detail but it seems complicated. I keep believing that there is a simpler solution. For instance, if someone has experience with the application of Similitude laws...
  2. BeFEA

    A scaled finite element model

    Hello! I have a question that I would like to share with you. Although there is little chance to encounter this problem in practice, I think it is good for a structural engineer to pause and ponder about it for a few seconds. For me, it is actually a real-life problem. Here it goes: - Let's...
  3. BeFEA

    Seismic Separation Question

    Hi xeneize10! Your question seems too generic to me. You have to perform a structural analysis to determine the maximum displacements of the structure. Depending on the complexity of your structure, you might not be able to complete your task with hand calculations.
  4. BeFEA

    Riddle-like question

    I think we reached a conclusion. I think the proof provided by KootK is correct and very nice. I tried to generalize it, and I reached to the conclusion that the drift ratios are related only by the ratio of the building heights, no matter what the mass of each building is! Again, this is valid...
  5. BeFEA

    Tied Rafter, Basic Determinacy Question

    Theoretically, a truss should not have continuous chords. Practically, the moment in the chords is zero when the structure is shaped like a stable "truss". The equilibrium of joints shows that there are no bending moments in such elements. Yours would not be a stable "truss" if you had full...
  6. BeFEA

    Strengthening existing RC slab

    Do you have noticeable vibrations on your slab? If you don't, maybe you can use fiber reinforced polymers to increase the hogging and sagging moment capacities. It is not very expensive for the quantities you will need. Check with your local providers.
  7. BeFEA

    Riddle-like question

    KootK, I am not 100% convinced for your analytical proof yet. Does your proof work if building 1 has distributed mass m1 and buildimg 2 has mass m2 (where m1 is different from m2)? Also, for the 6 storey building I think the highest drifts would be around mid-height.
  8. BeFEA

    Riddle-like question

    Sorry, I answered before reading your reply.
  9. BeFEA

    Riddle-like question

    The two buildings can have the same mass (OK, theoretically) but compensate with stiffness such that both buildings have the same fundamental period... Am I missing something here?
  10. BeFEA

    Riddle-like question

    But wait, why is #5 true? Since both buildings have the same period, the spectral acceleration should be equal for both. You are assuming that the mass of building 2 is twice the mass of buildng 1, right? This doesn't have to be true, am I right?
  11. BeFEA

    Riddle-like question

    Can someone think of a sound reason why the conclusion reached so far (larger drifts in the three storey building) can't hold for the general case?
  12. BeFEA

    Riddle-like question

    Thank you for your precious time. I ran time history analyses (linear and nonlinear) and they all showed that the drifts in the building with 6 stories are smaller. Now I invite you all to find a single example/scenario in which the drift ratios would be larger for the taller building, and...
  13. BeFEA

    Compression cube tests of grout

    I think you should specify the country or code you are referring to. I had never heard that two concrete cylinders were sufficient. I guess it all depends on the country and specific rules for your country.
  14. BeFEA

    Riddle-like question

    I need to make another clarification. When I say drift, I mean interstorey drift ratio.
  15. BeFEA

    Riddle-like question

    In order to be able to solve the problem, let's focus on buildings with uniformly distributed mass along the height. Even simpler, let's focus on buildings with the same mass in each storey. Are the drifts in the taller building always smaller?
  16. BeFEA

    Riddle-like question

    KootK, the first mode is predominant in the building under consideration. However, I would not like to narrow down the discussion to my specific case. I am trying to figure out if there is ground for generalization of the problem.
  17. BeFEA

    Riddle-like question

    Sorry for not pointing it out earlier, but yes, let's assume the mass is equal in each storey. I am trying various types of analyses, and I get the same result in all. Linear and nonlinear time history analyses, as well as response spectrum analyses show that the drifts are smaller in the taller...
  18. BeFEA

    Riddle-like question

    Thank you for your time JGard1985. I am afraid you are over-simplifying the problem. You are neglecting the distribution of the inertia forces along the height, you are neglecting the contribution of higher modes etc. And don't forget, we are talking about drifts, not the roof displacement. If...
  19. BeFEA

    Riddle-like question

    Thank you for your quick replies. The two buildings can have the same fundamental period, because like TehMightyEngineer said, they can have different stiffness. I added the detail regarding the "structural type" because I would like to say that the mode shapes are similar for the two buildings...
  20. BeFEA

    Riddle-like question

    Hello! I have a question for you. I am not sure myself about the answer, but I have some analysis results that make me totally confused. Therefore, the question will look like a quiz-show question or a riddle. Here it goes: - Let's consider two buildings with the same fundamental period, say...

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