Do you mean "silos made out of concrete" or "silos containing cement powder"?
Here in the US, if the silos are built by a specialty contractor routinely doing that kind of work, they could generally furnish the design for the foundation, provided an adequate geotechnical report is available. It's not always done that way, but is a possibility to look into.
Wind and seismic are liable to be major design issues, hopefully with some seismic recommendations coming in that geotechnical report as well.