Learning Forum

[Rommel Jr. Landicho]

Hi! I am currently modelling an RC Beam subjected to 4 point bending test for my thesis. Here are the following details:

Symmetry Region - (quarter beam)

Boundary Conditions

Input parameters for Menetrey Willam concrete

Input parameters for Steel

The parameters are all from related literature. 

Command snippet at Concrete body

TB,CONCR,matid,,,MSOL
TBDATA,1,2,1,1e-3,100,10,1e-20

My reference study shows that the beam should fail at 35 mm. However, my model still does not fail at 70+ mm. My criteria for failure is (1) Steel yielding or von mises stress of steel reaching 400 MPa and (2) Von mises stress of compressive face of concrete reaches 40 MPa. My problem is that even though my model converges, the von mises stress of concrete is only ~30 MPa at 60 mm which causes overestimation of midspan deflection. 

(1) Steel yields at 400 MPa 

(2) Concrete Compressive edge (critical location since midspan) still does not reach 40 MPa at 60 mm 

 

1) What can I do to fix this? Is there something wrong with my boundary conditions, input parameters, etc.? 

2) Would you recommend for me to use a different material model? I was wondering if I should just use Multilinear isotropic model for concrete with a solid65 element type but I am not sure if that can successfully model the softening behavior of concrete. I am also thinking if I should use Drucker Prager instead. 

3) Does anyone know what the command snippet above does? When I remove it, the model does not converge. However, I do not know what the values indicate. 

4.) Should I add another model for concrete that takes into account damage? To my understanding, Menetrey Willam is only a plasticity model so it does not sufficiently model post peak behavior (am I right?). Will doing this correct my problem on concrete compressive stress?

5.)  I will be modelling Fiber sheets afterwards. How can I set an ultimate strain for fiber sheets such that it fractures at that strain value? 

I would really appreciate any help. Thank you very much!

 

[Ashish Khemka]

Hi,

Please see if the following video helps: Reinforced Concrete Modeling - FEA using ANSYS - Lesson 9 (youtube.com)

Regards,

Ashish Khemka