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  1. Tygra_1983

    Natural Frequencies in ETABS

    Do you have any ideas what could be the problem then, Greg? I mean, I just build the model and run the modal analysis. EDIT: The reason there appears no shape is because it is oscillating in the direction into the screen, lol. I just discovered it.
  2. Tygra_1983

    Natural Frequencies in ETABS

    In modes 1,3,4,5 there is no shape. Etabs shows no displacement at all: Here, are mode shapes 2, 6, 7 and 8.
  3. Tygra_1983

    Natural Frequencies in ETABS

    Dear all I am trying to simply compute the natural frequencies of a 4 storey structure in ETABS. I am also trying to validate them in MATLAB. However, I am getting drastic differences in the results. This is strange because a couple of years ago I did a dynamics of structures coursework...
  4. Tygra_1983

    Help in ETABS Regarding the Storey Stiffness Option

    Hi all, I have download the 30 day trial for ETABS and practising with it. I am trying to find the storey stiffness in my model. To do this you go to Tables > Analysis Results > Structure Output > Other Output Items >Story Stiffness. However, the table comes out completely blank, as you can...
  5. Tygra_1983

    Calculating Axial Load in a Tire Beam

    Thanks, 3DDave.
  6. Tygra_1983

    Calculating Axial Load in a Tire Beam

    Here are the axial forces from thew SAP2000 model Here, are the bending moments. EDIT: I have gone for the apex being pinned, and from this I get the answer I was looking for. I have been following a book with a similar example and I thought the apex was fixed. rb1957, you answer of 20.47...
  7. Tygra_1983

    Calculating Axial Load in a Tire Beam

    Sorry, here is the equation with units: To clarify, the main diagonal structure is fixed at the apex. The tie beam is pinned. Also, because of symmetry I am only considering one side in the calculation. The load on the frame is 4kN/m. The upwards force is the vertical reaction at the pin of...
  8. Tygra_1983

    Calculating Axial Load in a Tire Beam

    Hi Greg, Hopefully, this diagram will clear some things up. The long equation is the moments taken about the apex. Sorry I see now, I made a couple of typos to the original equation. I am assuming anti-clockwise as positive about the apex, so yes, the first two terms are negative, but end...
  9. Tygra_1983

    Calculating Axial Load in a Tire Beam

    Hi, I have the following example where by I am trying to calculate the axial force in the tie beam: The geometry is: width = 10m, height = 8 metres, angle = 57.995 degrees. The diagonal members are 9.43m (sqrt(89)) And these are the support reactions: If the tie beam is fully fixed I can...
  10. Tygra_1983

    My Meshed Slab Does Not Transfer Load to Supporting Beams (SAP2000)

    Dear all I have this simple structure in SAP2000: I want the self-weight of the slab to transfer to the beam at the slab edges. The self-weight = 25 kN/m^3*0.2m = 5 kN/m^2. I have done the appropriate meshing, but the self-weight of the slab does no seem to be transferring to the beams...
  11. Tygra_1983

    Correct Displacements, but incorrect moments using the DSM for Structure

    Thanks rb1957.
  12. Tygra_1983

    Correct Displacements, but incorrect moments using the DSM for Structure

    Thanks for you reply, rb1957. After much staring at the screen and wondering why (lol) I have realised that you have to add on the fixed end forces/moments to the vector A in the code. Thus, for member 2 we get Member2_forces = [ A(1) A(2) + 600 A(3) + 4000 A(4) A(5) + 600 A(6) - 4000]...
  13. Tygra_1983

    Correct Displacements, but incorrect moments using the DSM for Structure

    Hi rb1957, 1) So, these are the fixed end moments. the UDL is 30 kN/m. Thus, for member 1 that is 10m long, the force at the node is 30*10/2 = 150 kN, and the moment is 30*10^2/12 250 kNm. For member 2 that is 40m long, the force at the node is 30*40/2 = 600 kN, and the moment is 30*40^/12 =...
  14. Tygra_1983

    Correct Displacements, but incorrect moments using the DSM for Structure

    Dear all, I have the following structure with its loading that I am trying to solve I am using the stiffness method, and my MATLAB code is below: clear, clc, close all % Structural properties E = 2.1E+08; I = 1022000/100^4; A = 620/100^2; EI = E*I EA = E*A alpha = atand(30/40) L1 = 10; L2...
  15. Tygra_1983

    Load Distribution on Elements

    Its just another phrase to emphasize that He will never stop taking care of you.
  16. Tygra_1983

    Load Distribution on Elements

    Thank you for your answer, BulbTheBuilder. And its great to meet another Christian on here. Just in closing If you love that verse in Deuteronomy, look at it when it is quoted in Hebrews 13:5 in the Amplified Bible: "Let your character [your moral essence, your inner nature] be free from the...
  17. Tygra_1983

    Load Distribution on Elements

    When I click the link it goes to 'page not found'. I will have look for that. Unfortunately, my student trial expires in about 10 days. Shame, I was starting to like Tekla Structural Designer. At Uni I used SAP2000 and was accustomed to using that. It took me a while to enjoy Tekla. Yes...
  18. Tygra_1983

    Load Distribution on Elements

    I didn't know why the loading was changing on the beam along its length (the one I labelled), and also all the beams at the same level that were parallel to it - members B to F. So, it has been answered somewhat. Wow, that's incredible. Praise God for your long life. I guessed you were retired...
  19. Tygra_1983

    Load Distribution on Elements

    Yes, BAretired, for those areas (not in red) I would use the loading for roof space, which on my loading sheet is 1.35*0.25 + 1.5*0.25 = 0.71 kN/m^2. I have learned that its good to group members, so I would use the same beam size for B-F. In regard to labelling the joists and wall etc I would...
  20. Tygra_1983

    Load Distribution on Elements

    Yes, sure, but I can tackle it as I go along. There are many other members in the house other than this one, and I am starting with the roof rafters and working down. My first thoughts were that the beam above the wall will take 14.5 kN/m and it will transmit 14.5 kN/m to the wall. This is...

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