Recent content by Tygra_1983

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.

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.

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...

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...

Thanks, 3DDave.

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...

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...

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...

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...

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...

Thanks rb1957.

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]...

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 =...

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...

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