Seismic check of a simple structure?

I have two containers put together on top of the other while supported on six precast concrete cubes at the base. Can some one out there help me with a step by step me formula on how to assess the vulnerability of the structure to show that its failing by calculations. The containers are bolted together and the zone category is 2A, while the soil type is gravel. You can view the type of the container on http://www.ics-group.net/Downloads/Prefab_Standard.pdf ,