Can´t load precast family slab into a revit file
Precast-Hollow Core Slab.rfa is a Structural Framing family. You would have to place it as a Structural Beam. (Most likely, multiple Structural Beams.)
Floors are non-loadable system families. Unless you really need to model each plank, you could create a Floor to represent the precast, hollow-core construction.
You may be able to place multiple parallel instances using a Beam System. I was thinking of placing them one-by-one using the Beam tool, on the Structure ribbon tab, on the Structure panel.
If you choose to place it as a Beam System, you would have to specify the Precase-Hollow Core Slab type in the Properties palette: not in the Type Selector at the top, but in the Beam Type property, under the Pattern category. You will also need to adjust the spacing to match the width of the precast framing member selected.
Here is where the family ends up in the Project Browser.
You did not say where you got the families in your original post. I assumed you were using the out-of-the-box Precast-Hollow Core Slab.rfa.
The families you posted are Detail Items, meant for adding detail to a Section through a floor to make it look like a precast-hollow-core slab.
How to approach this depends upon what you need from the model. If all you need is a representation of the mass of the precast concrete planks in the project, then duplicating an existing Floor (system) family in your model and editing it to appropriately reflect the depth of the precast (and any topping that may be poured on top) could be sufficient. At sections, you could apply the Detail Items on top of the Floor.
If you need to model every concrete plank, then using a Structural Framing family may be necessary. The US Imperial and US Metric content provided to users in the United States (and, possibly elsewhere?) includes both Precast-Hollow Core Slab.rfa and M_Precast-Hollow Core Slab.rfa, for imperial and metric projects, respectively. These can be found under the Revit Libraries folder: ...\Libraries\US Imperial\Structural Framing\Precast Concrete and ...\Libraries\US Metric\Structural Framing\Precast Concrete. The location of the Libraries folder will vary, depending upon how the program was installed. If you are outside the United States, you may have an equivalent family in the local content.
