See the top rated post in this thread. Click here

Page 1 of 5 12345 LastLast
Results 1 to 10 of 41

Thread: Verification of modal analysis Results

  1. #1
    Active Member
    Join Date
    2010-07
    Posts
    67
    Login to Give a bone
    0

    Default Verification of modal analysis Results

    Why If I solve one small model (concrete building 10 floors) by using Etabs and the same building By Using robot I see the different results for modal analysis from each program
    If the basics and concepts are the same in each one of them then why we get different results.

    I hope any one can answer my question

  2. #2
    Active Member
    Join Date
    2010-03
    Posts
    56
    Login to Give a bone
    0

    Default Re: Verification of modal analysis Results

    Please post more details about structure model and some details about the input and output from modal analysis.

  3. #3
    Active Member
    Join Date
    2010-07
    Posts
    67
    Login to Give a bone
    0

    Default Re: Verification of modal analysis Results

    Quote Originally Posted by medo View Post
    Please post more details about structure model and some details about the input and output from modal analysis.
    thanks for your helping
    But did you model any building by robot and Etabs and compare dynamic analysis result?
    I will try to post the model

    once again I have to thank you for your post and assistance

  4. #4
    Member
    Join Date
    2010-08
    Location
    İstanbul
    Posts
    49
    Login to Give a bone
    0

    Default Re: Verification of modal analysis Results

    My model etabs v9.7.1 and RSA2011 sp2
    results are same. ıts perfect run.
    no problem modal analysis. bye

    falconado
    Attached Images Attached Images

  5. #5
    Active Member
    Join Date
    2010-07
    Posts
    67
    Login to Give a bone
    0

    Default Re: Verification of modal analysis Results

    Quote Originally Posted by troy_the.best View Post
    My model etabs v9.7.1 and RSA2011 sp2
    results are same. ıts perfect run.
    no problem modal analysis. bye

    falconado
    I found one thing
    Sometimes when I use Riigid diaphragm With Salb (Flexible Rigid Diaphragm XY) I got this problem , I do not know why
    I think rigid diaphragm some times creats a problem with dynamic analysis

  6. #6
    Member
    Join Date
    2010-08
    Location
    İstanbul
    Posts
    49
    Login to Give a bone
    0

    Default Re: Verification of modal analysis Results

    Yes you are right. when use rigid diaphram or semi rigid diaph. its given wrong results. İ hope from autodesk this bugs is fix on next Sp3 patch. Good works.

  7. #7
    Active Member
    Join Date
    2010-07
    Posts
    67
    Login to Give a bone
    0

    Default Re: Verification of modal analysis Results

    Quote Originally Posted by troy_the.best View Post
    Yes you are right. when use rigid diaphram or semi rigid diaph. its given wrong results. İ hope from autodesk this bugs is fix on next Sp3 patch. Good works.
    Robot with a lot of Bugs!!!
    See, when I try to use Seismic Loads by Using UBC code
    and applied the value of base Shear say Vx = 1000 KN,
    I found that robot does not multiply the results with a scale factor to be matched with the new values

    For example :
    Static seismic load say = 1000 KN
    Dynamic seismic load say = 500 KN
    now robot should Multiply the Seismic dynamic load by factor = 1000/500 =2
    this as per UBC because dynamic loads should not be less than static load
    But Robot did not do that, and this is also one more Bug there.
    Thank you

  8. #8
    Member
    Join Date
    2010-08
    Location
    İstanbul
    Posts
    49
    Login to Give a bone
    0

    Default Re: Verification of modal analysis Results

    mechiel,
    look this jpg UBC scale factor in robot. have a nice days.

    falconado_turkey
    Attached Images Attached Images

  9. #9
    Active Member
    Join Date
    2010-07
    Posts
    67
    Login to Give a bone
    0

    Default Re: Verification of modal analysis Results

    Quote Originally Posted by troy_the.best View Post
    mechiel,
    look this jpg UBC scale factor in robot. have a nice days.

    falconado_turkey
    Hi falconado,
    thank you for your helping,
    But this is not hte scale factor,
    this is the direction of ritz vector
    when we apply the seismic in X direction we put X=1
    when we apply seismic in y dir we put Y=1

    After that we use a respondse spectrum curve UBC
    then program we calculate the seismic forces in X and Y
    then we will get Vx= 1000 say (Dynamic) ; and Vx = 500 (Static) say
    so all results of dyanimc seismic should be multiply by scale factor =0.5 = Vstatic/Vdyn

    Regards

  10. #10
    100 Club
    Join Date
    2009-10
    Posts
    119
    Login to Give a bone
    0

    Default Re: Verification of modal analysis Results

    Mech
    Maybe it can help you
    When u use directional X=2 it means that you have doubled seismic force in that direction

Page 1 of 5 12345 LastLast

Similar Threads

  1. Analysis Results as Parameters
    By Inventor Wishes in forum Inventor Wish List
    Replies: 1
    Last Post: 2012-10-06, 02:51 AM
  2. ROBOT Modal analysis results are different from other programs
    By erginc in forum Robot Structural Analysis
    Replies: 2
    Last Post: 2012-07-11, 08:05 AM
  3. Modal/seismic analysis problem:missing eigenvalues
    By dan.suciu488718 in forum Robot Structural Analysis
    Replies: 1
    Last Post: 2012-07-11, 06:39 AM
  4. modal and seismic analysis
    By mecheil2000 in forum Robot Structural Analysis
    Replies: 6
    Last Post: 2011-10-12, 08:58 AM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •