Isolated footings simulation

[perfectaccess]

Hi

I have small villa, which I assume it is has fixed foundation(isolated footings),but when I study the footings on FE model the model face huge uplift ,due to moment, and it is unstable, so I think the followings

1. For Isolated footings it is more logic to use pin connection in the model, since actually isolated footings will never prevent moment as in the case of piles
2. In this case I have to make the column to footings connections as pin (make the steel in the center of column, near column, footings connection s this the general trend in construction according to this assumption)
3.If I have building of seven floors with isolated footings(strong bearing capacity), can I assume the building fixed on the model, if the total vertical load is sufficient to prevent the amount of moment generated for earthquake(as it can be study on the footings model alone), and the footing is stable???
Regards

 

[jayrod12]

1)For most footings, isolated or not, the most prudent design is to start with a pinned base.

2) Your connection detail should be a typical base plate and anchor bolts, don't think too hard about it, if you make the connection a little too robust, the footing will rotate slightly to create the pin.

3) I would be inclined to say no. Your building will have a series of pinned supports, it will not be a fixed base.

4?)You can't account for the total vertical load when checking against overturning, in fact, you have to account for no live loads and a reduced dead load.