## Forum

### Problem with comparison of deflection

1. I'm doing a 3 pts Bending analysis and I would like to compare the deflection between 3 Results.
First using the Beam Theory

Second using GEBT

and Third using Helius Composite.

In the file <.pnj> you can see the kind of analysis.
In the file <.xlsx> you can see the comparison between the 3 results.

In the file <.txt> you can see the Gebt input file.

I would like to know why there are differents in  deflection between gebt and the 2 others.
Please can you look at my gebt file and tell me if there are some errors.
I applied the same case for all.

2. For GEBT, do you use a linear analysis or nonlinear analysis? Another check, GEBT uses Timoshenko model, the other two methods might use E-B model. Transverse shear will contribute to the deflection. You can let the 2nd and 3rd diagonal to be zero to trick GEBT to use a E-B model. ---- Emailed forum response from wenbinyu@purdue.edu
3. Even if I use linear or nonlinear analysis, it's the same What do you mean about linear or non linear. Is it geometrical linearity ? ---- Emailed forum response from s.chaibi@thinplytechnology.com
4. Yes, GEBT has the option (one of the flags) to use a geometrical nonlinear or linear analysis. I believe the main reason is that transverse shear which is missing from the other two methods. If you follow the trick I mentioned in my previous trick (zero 2nd and 3rd diagonal term), I will be surprised that GEBT will be different from the two other methods. The transverse shear-induced bending could be important because it is a nonuniform bending. If you compare the results with a 3D FEA, you will find out that VABS+GEBT results are more accurate. -----Original Message----- ---- Emailed forum response from wenbinyu@purdue.edu
5. Salim,

Your analysis is a linear analysis. As Prof. Yu pointed out, you are using a Timoshenko model in GEBT while other two are Euler-Bernoulli beam model, in which shear does not take into account. GEBT can also model a E-B beam by setting the shear stiffness constants ,(2,2) and (3,3) in your stiffness matrix, to 0. I tested on my end and the center deflection by GEBT is 8.4242045E-01, which agrees with other two models very well.

Qi