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  1. civil2013

    get coordinates of a line in 2d from dxf file

    One doubt, should i be searching for 'LINE' or 'AcDbLine' . If i extract the line one after the 'AcDbLine', i believe i will get the coordinates. Correct me if wrong
  2. civil2013

    get coordinates of a line in 2d from dxf file

    Hi all, I have a drwing in .dxf format. its a 2d line sketch. The drawing has only 2d lines. It is basically the center line (through the wall) for the plan of a building. I wish to get the start and end coord of each line in this drwaing. i am using AutoCAD LT 2020. Is it possible to get this...
  3. civil2013

    fortran for graphics

    Hi, I need to built a 3d model using x,y,z coordinates..sample model prepared in a software is attached here.. the model might have 100nodes, of which not all coordinates are connected to each other.....I get the coorindates generated in my fortran95 program. I am using fortran tools6.1 which...
  4. civil2013

    Variables in fortran & array use

    in that case, ...is it possible to have an array'k' which is 10 x 1 and can store all 10 nxn matrices in this. .. is it possible to store 2d arrays as elements in a 1d array
  5. civil2013

    Variables in fortran & array use

    hi, to simplify, my problem looks like this - the program asks for an integer input 'n'.. when I enter 'n'=10, a variable k1 gets assigned as '1'. k2=2, k3=3, k4=4.... and so k10=10. I understand that we could define 'k' as a allocatable 1d array. but I do not want to use array here, depending...
  6. civil2013

    Variables in fortran & array use

    Hi, I am using fortran95 for writing a code.my doubt are: 1. Whether it is possible to autogenerate a variable. Ie; for i=1, the variable should be k1, then k2 and so on... 2. I have 2d arrays k1, k2, till k10 which are of nxn size...is it possible to have an array'k' which is 10 x 1 and can...
  7. civil2013

    simple frame analysis by stiffness matrix approach

    your comment noted. regarding my pgrm,i have not decided what all to extract as output. if your worry is about plotting the outputs, u cud use libraries from softwares like plplot/gnplot etc... they sync with fortran/python etc
  8. civil2013

    simple frame analysis by stiffness matrix approach

    hi, its not part of course...i am trying to develop a fortran code for analysing frame structures, just worried how to handle the self weight in the analysis.. all the other external loads are resolved as joint loads.. doubt is regarding how to take care of the column weight - if the column...
  9. civil2013

    simple frame analysis by stiffness matrix approach

    hi, i am analysing a simple frame structure - composed of a horizontal beam and a vertical column (the frame looks like '7' with 6 dofs restrained at the bottom of column)... i have prepared the stiffness matrix for the strcture, now need to prepare the force matrix..... i need to analyse the...
  10. civil2013

    natural frequency from eigen analysis

    hi kootK, PittEng88, any update/suggestions on the thread. thanks,
  11. civil2013

    eigen vector for generalised eigen pblm.

    hi, i am trying to solve the vibration(free) of a portal frame by hand, i calculated the eigen values and calculated the eigen vectors for the std eigen problem, how do i get the eigen vectors for the generalised eigen problem to finally arrive at modeshapes.i cross checked the timeperiod using...
  12. civil2013

    eigen vector for generalised eigen pblm.

    hi, i have a generalised eigen value pblm,which is of form (A-λB)x=0... so i converted it to std eigen format, now the pblm is (B^-1.A-λ.I)y=0... how do i transform the eigen vectors of this std format to the eigen vectors of 'x'. thanks.
  13. civil2013

    natural frequency from eigen analysis

    hi,i am putting my thoughts/reply below in blue 1.) You said that you are looking to analyze a cantilever column, which you split into two elements (3 nodes). When you do this you should only have a 4x4 stiffness matrix due to the boundary condition of the fixed support. Considering the other...
  14. civil2013

    natural frequency from eigen analysis

    hi, basically I used two methods to solve the [K]-w2[M]=0 eqn. method 1: I retained the generalized eqn, then used the command genvals(K,M) in Mathcad to get the Eigen values and genvecs(K,M) to get the Eigen vectors method 2: I multiplied through out with [M^-1] and so the eqn is now of the...
  15. civil2013

    natural frequency from eigen analysis

    hi PIttEng88, i am attaching the mathcad(PTC) file along with the pdf copy too.i have given my explanations on the same, kindly review and get back to me. thanks. https://drive.google.com/folderview?id=0B9gSrTCMo9R3d3lkeWJnMkZjNzA&usp=sharing
  16. civil2013

    natural frequency from eigen analysis

    hi PittEng88, what made u think that i have put the eqn backwards... i meant (K-w2M)x as u have mentioned, did u notice any place where i mentioned other ways? appreciate ur help.. thanks.
  17. civil2013

    natural frequency from eigen analysis

    hi, i found the soln myself.. just by multiplying throughout with m^-1, i converted the generalised eqn to stnd eigen format and then it was easier... i am using mathcad to get the eigen vectors, when i calculate the eigen vectors using the command - genvecs(Kr, Mr) - where the Kr, Mr are the...
  18. civil2013

    natural frequency from eigen analysis

    hi, i still face some problmes... my eqn to solve is of the form K-w2M=0 which is a generalised eigen eqn.. the matrix is of 6x6 size... whats the easy way to get the eigen pairs.. any handnotes on how to convert this to standard eigen eqn format ie; A-lamdaI=0 ?? appreciate your assistance...
  19. civil2013

    natural frequency from eigen analysis

    thanks guy, i have found the soln myself... the matrix was converted to diagonal form, and then the soln was easy..could you guys give me a link/note on rayeligh and any comparison with eigen analysis.. appreaciate your help... thanks.
  20. civil2013

    natural frequency from eigen analysis

    Hi, i am trying to find the natural period of a vertical cantilever beam which is fixed at bottom and free at other end., i worked out the global M & K matrices and i have the eqn in the form [M]-w^2[K] = 0, the M & K are not diagonal matrices, but square symetric matrices of rank 6. i...

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