fbd-Ite problem

[seismosoft]

Tracy,

If you have unchecked the 'Do not allow element unbalanced forces in case of fbd_ite' option, then you might get other divergence messages, but you should not get an fbd_ite message. Can it be that you unchecked the option for the other element type (infrmFB vs. infrmFBPH). There are two such options.

SeismoSoft Support

[Tracy]

Yes, I unchecked both, but the 'fbd_Ite' messages still come out, I think because of the too small elements in the column while using 'infrmFB' element.

May I know is it possible to set up the nodes attached to the column without separating it in Seismostruct. For example, I defined Node 1 (0,0,0),Node 2(0,0,6), Node 3 (0,0,3),Node 4 (0,2,3), the column is defined by N1 & N2, the beam is defined by N3 & N4, Node3 is attached to the column but does not separate the whole column. Can I achieve it in SeismoStruct?

[Tracy]

Hi Salar,

I appreciate your advice. I think I would keep working with SeismoStruct.

You are right, use inelastic elements for plastic hinge length,and elastic elements for others. But the same problem should be solved since there are many nodes in the inelastic elements in my case.

Tracy
quote:Originally posted by salar

Hi tracy
your work is really needed to be verify by other software like ABAQUS.
I recommend you:
suppose your pile remain elastic behavior because of confining of soil so,Try to have one example in elastic Pile element with nonlinear link for behavior of soil and nonlinear element for column.
Then see your result.
Your work need trail and error solution to get which element can get the best result. maybe with elastic pile you can get well result!

[huffte]

Hi Tracy. I wonder if you could try one or both of the following:

1. As mentioned in one of Rui's posts, is it possible that displacement-based inelastic elements could help in such a situation? Maybe you have already tried this and I missed it, or maybe you have a specific reason that displacement-based elements won't work. I'm not sure if this has been explored.

2. Could you simply reduce the mesh. Make longer elements and increase the lateral springs accordingly? Six 36 inch elements or nine 24 inch elements might give a close approximation to the solution? You might even plot the solution versus element size and get some idea of the influence. Perhaps you've already tried this and I missed it as well.

Simply thoughts of the top of my head Tracy. I hope you'l find a solution soon. Best of luck with your work.

[Tracy]

Hi Huffte,

Thank you for your kind help. The behavior of force-based element and displacement-based element are different, one of my interest is to compare both. In my case, there will be a lot of springs attached to the column, that's why I need to define many nodes along the column.

Now I am wondering is it possible to set up the nodes attached to the column without separating it in Seismostruct. For example, I defined Node 1 (0,0,0),Node 2(0,0,6), Node 3 (0,0,3),Node 4 (0,2,3), the column is defined by N1 & N2, the beam is defined by N3 & N4, Node3 is attached to the column but does not separate the whole column. Can I achieve it in SeismoStruct? Thank you.

Tracy

[seismosoft]

No Tracy, it cannot be achieved. You have to defined two vertical elements elem1(Node1-Node3) and elem2(Node3-Node2). Only then the beam and the column are connected.

SeismoSoft Support

[seismosoft]

Note also that in the case of very small element lengths (one or two times the section width) the force-based elements will find extreme difficulties in converging. In such cases, it is advisable to employ the infrmDB element type.

if you want to compate the two element types infrmFB and infrmDB then you need to compare models with longer infrmFB elements and models with shorter (and more) infrmDB elements.

SeismoSoft Support

[khajehdehia]

Dear seismosoft support

I have problem with this model , I analyzed this model with applying dynamic time history load ,in this case there is no problem ,but when I want to run the push over analysis the fbd-ite massage appears I use the force-based element for column , and release property for beam ,i read your recommendation in the forum and i applied all of them but they didn't work ,i also changed the column element to Displacement -based element but at this case Max-tolerance massage appears ,therefor I send my model file to you please help me.

best regards

[z.gronti]

Dear khajehdehia,

It seems that the convergence difficulty is purely structural (high axial loads). An indication to this is to disable the "Include Geometric Non-linearities" check box and the analysis will be completed.

SeismoSoft srl

[khajehdehia]

Thanks a lot for your recommendations It works well, but I want to consider the geometric non linearity to obtain the realistic behavior of model ,how can I overcome this problem?

regards