Ultimate load deflection curve

[Shz713]

I want to simulated the ultimate load failure pattern of a simply supported reinforced cocnrete beam to have validated Abaqus model.

I have all the material data and carried out static load cases finely and verified the model accuracy. Now I want to simulate the loading as that of experiment, namely load the beam until complete failure occurs. My confusions are below:

1-To define load displacement amplitude for my loading, what amplitude I should provide? Also, will the analysis stop when the material limits exceeds or when the loading rate defined in amplitude curve is finished?
Let's say I don't know the ultimate failure load and I just want to load it till failure occurs (viz. defined material limits are exceeded).

2-I have two point loads to impose on the beam for loading, however the value of each load is dissimilar. In that case, should I use two different amplitude for each load?

3-To avoid stress concentration and singularity, I placed very tiny solid elements (0.000254m thick) to distribute the point load as patch load with the properties of beam. However, I don't want to have the mass of the plates be added to the total mass of structure, in that case if I want to use very low stiffness and density to eliminate such effect the analysis stops at initial increments due to excessive deformation of loading plates. What can I do to have the function of loading plates only for load distribution and no stiffness contributed? I tried to convert the point load to patch load but the max displacement are not same ( so am assuming the loading plate is giving some marginal stiffness to structure which should not be the case!).

At the end, I want to get ultimate load capacity of beam such as figure below. I did pushover analysis in structural software but never in Abaqus. Any comment would be sweet!

Cheers,

Shoot for the Moon, even if U miss, U still land among Stars!

 

[Mustaine3]

1. What is definition of "failure"? Have you added any criteria into Abaqus?
Why are you talking about an amplitude as it has to do something with the behavior of the structure? It is just a load vs. time multiplicator. The load-deflection curve has nothing to do with that. The default amplitude (Ramp) is totally fine in a typical static analysis.

2. Why is it dissimilar? The structure looks symmetric, the load too. Is the material unsymmetric or why is the behavior unsymmetric? And to answer your question: With the default amplitudes you can get dissimilar results, when the deflection is different. So again, I don't see a reason why a non-default amplitude should be specified.

3. You could add a small face partitions and apply the loads as pressure. Or you add a coupling at each side, so the load at the ref node is distributed to a number of nodes on the structure.

 

[Shz713]

Thanks for your comment.
1-What I meant was that I want to see at what point/stage the beam cannot carry load and it becomes fully plastic or collapsed. To do that, I need to have a loading rate right? This loading rate is applied as displacement control/force control. So my question is how I should define the loading rate so either: analysis stop when material limits exceeded or predefined load or displacement is reached in the beam?
Assuming I don't know what would be the max load than beam can undertake, in such cases what is the best practice to find out the loading amplitude.

2- You're right, the structure is symmetric, but the loading value is not. This is representing axle loads from truck, so front and rear axles have different values.

3-I did add the gasket size to be same size as the tire of truck (0.2*0.4), but when I define very low material properties(E 0.1, Density 0.1), the results is different for static point load compared to the case where I use proeprties of beam for loading plate. The only function of loading plate is to distribute the load and nod contribute to mass or stiffness of the beam.

I've figured out that I need to use Dynamic Explicit for my analysis and I prepared all the material models for elastic and inelastic stages. I just cannot work out above issues

Cheers,


Shoot for the Moon, even if U miss, U still land among Stars!