Girder to column connection with bearings in bridge

[Anonymous]

Hey guys

I am about to model a simple concrete precast girder bridge, 2nd Kavala Ravine (Greece) as my MSc dissertation to evaluate the seismic performance of the bridge upon few analysis procedures such as "equivalent force method", "pushover" and "response spectrum". 

Now I am just wondering how to model the connections considering bearings. can anybody please take a look at the model and tell me if the results are reliable and what the model lacks ? The attached PDF has also contain some pictures and details about the project.

Best Regards

[Rafacascudo]

I use to do the following.

1- No main girder offsets. Beams and other bars (including bearing) on their real position . They will be connected through rigid links

2- bar representing bearing should be a VERY rigid bar. All elastomeric flexibility will be done through elastic bar releases (you choose directions and values according to your needs) assigned to the "bearing"  rigid bar on its top node end.

3- Remember that bar releases are assigned for local bar directions !!!!

It would be something like picture below

[Anonymous]

Hey Rafael, thanks for the reply buddy. 

What I did was modeling the bearings as simple bars with the exact dimensions of bearing, and also similar material properties such as E, G, poisson ratio. I have no more technical details regarding them, and I have no idea how to calculate their stiffness in 3 main directions. I noticed you put 200 N/m as the stiffness value in elastic releases tab.

Regards 

[Rafacascudo]

Sorry for the delay.

200 was just a random number.

I use for horizontal directions

Kh=G*A/h, A is the "square" area, h is the thickness of the bearing pads (sum of ONLY the rubbers heights).

In the vertical direction infinite stiffness can be assumed.

If you want to consider the rotational stiffness , than it gets more complicated. I have never done it . See this thread here http://www.eng-tips.com/viewthread.cfm?qid=252203