Bridge Bearing stoppers

[SotirisLcivil]

Good evening,

I am trying to model a bridge with bearings, and I want to put stoppers on the bearings. By stoppers ( because I dont know if I'm using the right word), I mean an element that will stop the bearing displacement when it reaches its fracture limit, and will transfer the forces directly to the columns. I would also like to make it bounce when I'm using a Dynamic Time-History Analysis, so that I can measure the vibrations that would be induced.

For that purpose, I'm using a gap-hook element. Am I making the right choice? And if I am, what should the gap-hook stiffness be? Is it safe to keep the value that the programm already has (1,0000E+012)? Please ask me if I'm not explaining something right ( I'm a student and I'm new at this).

Thank you very much.!!!

[huffte]

I believe that the gap-hook element should model the behavior you describe. As to the stiffness, you can check whether or not whatever value you use is adequate or not by looking at the results. The deformation in your gap-hook element at maximum load should be very, very small compared to the displacement of the top of the pier. On the other hand, using too large a value could theoretically create convergence difficulties. So, you could try the default value. If it runs fine and if the gap-hook deformation is, say 1/100th of the pier displacement, then you've got it.

Best of luck, SotirisLcivil.

[SotirisLcivil]

Mr. Huff,

Thank you very much for your immediate and thorough response, I appreciate it deeply and it was very helpful. I do have two more questions though.

First of all, the gap-hook deformation is indeed less than 1/100th of the pier displacement but only in two directions. In the other direction is equal to the displacement limit that I have set to the element. I suppose that this is correct??

And second, the analysis stops and the following warning box appears : “Problem encountered in the solution in the controlled DOF procedure.” Moreover, there is the warning in the analysis log “current control type terminated”. Do you know anything about this? Thank you again for your time and help.!

[huffte]

Regarding the first issue, I believe that you are correct - the within-element displacement of the gap-hook would be equal to the specified gap.

As far as the second issue is concerned, I am afraid I haven't encountered that before. It seems that you are applying displacement controlled-pushover? I wonder if adjusting the target displacement, or using a different control scheme might help solve the problem. I'll be curious to learn of the outcome.

Best of luck, SotirisLcivil.

[SotirisLcivil]

Yes I am indeed applying displacement-controlled pushover.Therefore I will try what you suggest and hope for the best. I'll keep you updated. Thank you again for your immediate help and answers, they were valuable to me.

[z.gronti]

Dear SotirisLcivil,

Would you like to send us the model with the “Problem encountered in the solution in the controlled DOF procedure.” warning message at z.gronti@seismosoft.com in order to check it?