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VABS force/moment derivative terms

  1. Meryem Nisa Ataç

       While I am working on VABS, I get confused about when we should include derivative terms since there is no example problem provided in example files. I get internal forces/moments from GEBT and put them into the VABS input file. Even if the load is distributed, as far as I know, GEBT does not give derivative terms of forces/moments. Does it mean we should not only put internal forces obtained by GEBT but also the derivatives of them (by performing hand calculations) when we have distributed load?

       I would appreciate it if you could help me handling this error.

       Kind regards..

  2. Aref Fahadan Hajipour

    Hi friend..

    I need VABS . I search it but i can't find it's codes . Can you send me yours?! .. I will be grateful ..

    My E_mail: Arefhajipour@gmail.com

     Kind regards..

  3. AnalySwift LLC

    Hello Araf,

    Thank your or your interest in VABS.  You may request the VABS code from info@analyswift.com or access it online through the following links below.

    1. Request to join the VABS group at https://cdmhub.org/members/groups/vabs.  Here you will be asked for some very basic export information to join the group and access the software (also below, if more convenient to reply directly):
      • Names of engineer(s) evaluating VABS
      • Organization name 
      • Physical address of organization where VABS will be used
      • Type of entity (private, government, public, military)
      • Nature of business (what does your organization do?)
      • Number of years organization has been in business
      • Specific end use of VABS (what will you use VABS for?)
      • Civilian or Military Use (or both)?
      • Should we also send PreVABS (preprocessor to VABS, which is not yet part of the cdmHUB)?
    2. Once approved, launch VABS from the following link: https://cdmhub.org/resources/vabs
  4. Wenbin Yu

    Nisa, the derivatives for distributed forces/moments are applied loads. They are given. You can evaluate them by hand. They are different from those obtained by GEBT, those are internally force/moment resultants.

  5. Meryem Nisa Ataç

    Thank you Prof. Yu. I am going to prepare a simple input file for it.

    Kind regards...

  6. Meryem Nisa Ataç

    For example, beam in the attached file, we have uniform distributed load f. As far as I understand when we want to solve this problem, we can use F1 M1 M2 M3 F2 F3 (let’s say large_F) or f1 f2 f3 m1 m2 m3 (let’s say small_f).

    (I use the same notations in the VABS-manual.)

    Large_Fs are the internal loads applied in the cross-section. They can be obtained from GEBT by writing the external loads in the input file. This is how I perform my analyses.

    What about small_fs? As I understand from what you said, they are the external loads; but I do not get the logic behind the giving external loads in the cross-section since in VABS we do not define the whole model. If they are the external loads, are they calculated by f1=f*x (x=location of the cross-section we are interested)? If no, how should we calculate these small_fs?

    At the end, large_Fs and small_fs give the same stress output, right?

      Thank you..

    beam model

  7. Wenbin Yu

    Internal forces/moments will be the major contributors. Small f/m and their derivatives are also needed to recover stresses but not major contributor. You need to read the recovery theory about VABS to find out why. Briefly, when I transform to Timoshenko model, we need to use 1D equilibrium equation, that introduce f/m into the VABS formulation.

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