Good morning pavlo,
Thank you for your help. Below I will try to explain my choices.
- Reply to Point 1:
I define the BC in each interval because it is more comfortable for me, since I don't understand how to assign an ID to a condition (boundary, load or anything else), then currently I am not able to use te tab "Additional Load Cases". If this can affect the results of the analysis, could you explain me how can I assign an ID to a condition? In general, I need of a guide about the management of the Additional Load Case tab.
I am learning to use ATENA Science + GiD, but I did not find any reference in the related manual or in the troubleshooting manual about this issue.
- Reply to Point 2:
I will send you the model with the description of I want to do in each interval and further details in order to help you in the understanding of my problem.
- Reply to Point 3:
About your comment in Int 2: In general, I apply the loads (prestressing, displacements etc...) as unitary loads and then I apply the multiplier in the interval data because I don't know hot to display in GiD the magnitude of the applied loads then, in this way I know that they are applied to the model as unitary loads and then I read the multiplier in the Interval data (clearly it works if I have just 1 load per ecah interval, as in this case). If there is a way to display the magnitude of the load in GiD, could you explain to me how to do it?
About the application of the loads in terms of force or displacements: I apply force in Interval 1 and displacements in Int 3,4,5 because I think that it is better (in Intervals 4 and 5) to execute the test in displacement control in order to avoid convergency issues due to the nonlinear behaviour developed in these intervals.
About the further horizontal constraints applied in Interval 4, I have added them because in the simplified model (that I have modeled before to run this test) I have found that for high axial displacements (in tension), the model showed a non-symmetrical cracks pattern (probably due to numerical rounding) which led to non-symmetrcial displacements f the structure (even if the loads, the geometry and the mesh are symmetrical). Then I have decided to apply these constraints, checking that their presence did not affect significatively the stress distribution in the model.
About your comments in Int 3 and Int 4: I divided the displacement application in two intervals because with the displacement applied in Int 3, the structure has still a linear behaviour while, with the additional displacement applied in Int 4, concrete reaches the tensile strength and then I subdivided this interval in more steps in order to avoid convergency issues.
About your comment in Int 5: The magnitude of the displacement is correct, since I want to evaluate the behaviour up to the failure in tension of the reinforcements. In particular, I have assigned an ultimate strain to the reinforcements equal to 2.5%, having the bars a length of 7.6m (ecxluding the parts in correspondence of the steel plates) they have an ultimate elongation of about 0.025x7600mm=190mm, very close to the sum of the displacemens applied in Int 3,4,5=175mm.
- Reply to Point 4:
Self weight it is not applied because I am not interested about its effect.
- Reply to Point 5:
There is not any switch from unbonded to bonded because I had some troubles in the definition of this switch then, in order to simplify the analysis, I have found a way to bypass the grouting of the tendons by redefining the loading phases and by translating the consitutive laws of the materials used for the tendons (You will find more details in the notes that I will send you privately after this reply).
- Reply to Point 6:
In general the phases of my model are the ones identified by you. About your recommendations, I can follow them but, as I have already said in the Reply to Point 1, currently I am not able to use the additional load case tab then, at this time I do not know how to manage additional load cases in an interval.
- Reply to Point 7:
This model is referred to an actual structure, but I prefer to give you further information privately. You will find them in the notes of the GiD model that I will send you after this reply.
- Reply to Point 8:
Up to now this condition does not seem to affect the convergency, since I see concentration of stresses near the interface between elastic concrete and the actual concrete, while at the end of the reinforcements this concentration seems to be less conditioning, also because I have modelled two steel plates at the beginning and at the end of the model in order to spread the stresses. In any case, if you think that they can affect the results, could you help me to model the anchors for the reinforcements?
- Reply to Point 9:
This is what I expect in reality, even if I know that this could lead to convergency issues specially for the concrete elements far from tendons or reinforcements.
I want to ask you if I can send you my model privately this time, since it contains confidential information. Could you igive me an e-mail address?
Thank you for your support, I am available for any further details.