modeling of elastomeric bearing using SAP 2000

[bhowmik]

Does anyone help me about modeling of elastomeric bearing below bridge girder using sap 2000? How can it can be modeled, what type of link support type to be used for it, what will be its mass, weight, effective stiffness, what will be the six degrees of freedom? Thanks in advance...

[Amobin]

Does anyone help me about modeling of elastomeric bearing below bridge girder using sap 2000? How can it can be modeled, what type of link support type to be used for it, what will be its mass, weight, effective stiffness, what will be the six degrees of freedom? Thanks in advance...

Model thems as two point link support, fix only translational degrees of freedom. If u want a roller joint in any direction release u1 or u2 as the case may be. For stiffneess, G is the parametr, can be taken from AASHTO in relation to the duron thickness, normally 65 duron is the common choice for bridges

Amobin

[bhowmik]

Thank you Amobin. But elastomeric bearing is not totally restrained against translation. It has ability to translate in all direction up to certain extent.

[2Short]

You ca input a rigidity/displacement graph in SAP and it should be something like this:



At the maximum bearing displacement you input a very large value for the rigidity.

[2Short]

Correction, the graph should look like this:



Sorry, my bad :wacko2:.

[EMMANUEL]

pls. could you send me a simple bridge model illustrating how bearings are modelled using SA2000.

Thanks
Emmanuel Ita

[di_si]

Hi all!

You can use either Linear Links or Multilinear Plastic links, depending on your needs. (Go to "Define" Menu --> "Link Support Properties"). I'd say that if you're modeling for service limit state analysis, you would try to keep your bearings away from "yielding", so you could use Linear links, entering U1, U2 and U3 rigidity data. You'd be still in a linear approach. If you have share keys placed in such way that you avoid bearing yielding, you should add a Gap link to simulate the shear key. I would never use models from posts #4 and #5, because they increase secant rigidity and lead to erroneous bearing behavior. The increased rigidity must be provided by the Gap link. Multillinear Plastic links should be used only in Time History analysis cases, if share key collapse is considered. The bearings in this case would be responsible for transferring all horizontal forces from deck to foundations. I would still choose for U1 a linear behavior, and for U2 and/or U3 a Hysteretic behavior according to the desired scenario.

Once links are defined, the easier part is to draw them, first of all creating nodes to represent your bearings and your share keys, 2 per element. Afterwards, using "Draw" --> "Draw 2 joint link" and choosing the desired property, place your links accordingly.

Regards!

[di_si]

Instead of "share keys", please read shear keys. Regards!