Pre cast slab as Diaphragm

[Enhineyero]

Hi all, I am going to use a pre-cast slab as my floor for my structure. May i use it as structural diaphragms to transfer lateral loads (from EQ and wing)? what are the things that i should check to ensure that my pre-cast slab can behave & Resist the horizontal loads (including connections of insitu and pre-cast concrete) that it will transfer to the columns?

 

[JedClampett]

the answer to your question is yes, precast can be used as a diaphragm. Usually precast (is this precast only or prestressed, like double tees or hollowcore?), has standard design details like dowels that tie it into shear walls. The precast is set into place and the ends are grouted such that the dowels are connected to the precast. Sometimes, you need to apply a lightly reinforced topping to get the shear loads transfered or attach the panels to each other with weld plates. You need to get the PCI Design Handbook for some examples. Most standard precast has allowable shear loads. Or you can post them on your drawings and let the precaster's engineer design for them.
You do confuse me with your statement about columns. Precast is more likely to be used with a bearing wall/shear wall system. A column system would have concentrated shears at the columns which would be difficult to transfer with dowels or other standard details.

 

[Enhineyero]

Hi jed, thanks for your reply. I am using pre-cast slab hollowcore. i am just wondering if there is a special detail with regards to the transfer of lateral load (from the diaphragm) to the insitu beam?

i have not done much of precast works (except for walls, which i consider only as a load in the analysis) that is why i inquire of this.

 

[JedClampett]

The link below has some nice illustrations. But other manufacturers have slightly different details.