ductility of PT flat slabs with shear walls

[aldorankin]

I have a question concerning the behavior of the PT slabs, specially for the flat plate system. If Im working with a building that his primary lateral force resisting system are reinforced concrete shear walls, and my default building code is the ASCE 7/95, the reduction factor for the seismic forces is 5.5, but this factor doesnt work correctly for structures that has a low period of vibration, because they dont have the same capacity of energy dissipation as the long period structures. Lets say that Im working with a structure that has a low period, can I use the Rw factor just the same as the ASCE recommends on low period buildings, or do I modify it, lets say use Rw=4.5, in order to take into account lack of energy dissipation that the PT slab could have. And should I reduce the Cd amplification factor for the elastic deformation in order to be equal to the Rw, since those values are the same on the ASCE standard.
what is your recommendation.

 

[Taro]

I'm a bit confused by this post. Please expand on your statements that "(short period structures) dont have the same capacity of energy dissipation as the long period structures" and "lack of energy dissipation that the PT slab could have". If possible, please include supporting documentation or references.

 

[JAE]

I would think that you should use Rw = 5.5 for a Building Frame System with Reinforced Concrete Shearwalls. The behavior of this kind of building, in terms of seismic resistance, doesn't depend upon the flexibility (i.e. "energy dissipation capacity&quot of the PT slab. Rather, your primary mechanism is that of a rigid diaphragm (the PT slab) transfering load through a shear connection to the shearwalls and then to the ground. The PT slab does not "participate" in the seismic resistance but only must be "compatible" with the seismic deflections that result. Thus, you design for the Rw = 5.5 for the diaphragm/shearwall lateral design, and then make sure that the seismic deflections on the slab will not fail the slab.

 

[aldorankin]

thanks a ot for the advice JAE, I was thinking of that too!!! I just wanted to see what other opinions you guys could drop

tanks again

 

Dear all
Suppose no shear wall exists and the building resists lateral force via frame of column and slab in this flat plate building. What should be the reduction factor of seismic action.
Thanks for any advice

 

[chiba]

Suppose that no shear wall exists and the flat-plate building has to resist the lateral force via frame consisting of column and slab. What should be considered as the reduction factor of seismic action in this case?

 

[aldorankin]

dear biten and chiba :

in the case you are presenting, of the flat plate and columns only, the first thing is that on the structure you are using I would not recommend it as high as 3 to 4 floors, because to control the deflections on the structure should lead to larger columns. On the Rw factor, I should recommend a low factor I would use a range of Rw from 2.0 to 4.0 depending on the importance of the structure and the seismic zone you are in, I would not recommend it on high seimic zones. Remember that the PT slabs are generally slender and very flexible and you should take care of the deflections when analyzing this type of systems. Also check the additional steel that the slab will require due to the lateral forces.