Expansion Joints

[Ehsan1199]

I have a quite big structure and restriction of using shear walls made me to come up with idea in order to reduce the period (modes) of struture. I divided the strutural system that I had into two sub- structures and I used expansion joints in the slabs (15 floors) in order to keep the two sub-strutures as a unit.

Now my question is how can I introduce or define such this strutural system including the expansion joints in ETABS?!!!

How expansion joints can be define in ETABS?

 

[slickdeals]

I would analyze the sub structures as two separate structures. The reason being that if the lateral system is separate for both buildings, why do you want to model expansion joints and complicate the model?

If one building has a haunch supporting the other building slabs/beams, then I would model the "supported" building on rollers and apply the reactions as a point load on the "supporting" building.

 

[Ehsan1199]

Thank you for your reply Slickdeals!

What I got from your reply is to create two separate ETABS models. The main problem here is, I can not study the period of the complete structural system any more!

I tried to cut the model and create separate columns and beams at the common area of two sub-structures! Still ETABS take the diaphragm as same as the diaphragm of the model which was not separated. furthermore, the values for the period of structure increased and does not make sense.

 

[slickdeals]

Post your model.
You will need to reassign the diaphragms in the sub model.

If you are fully separated at the expansion joint, then you don't need to study the period of the complete structural system. Each portion has its own lateral resisting system and mass. The period depends on those two parameters.