Staad Foundation

Hi. I am having trouble with Staad Foundation.  I created a Tank foundation to analyze. The storage tank roof has a lot of elements such as the W section under the tank roof plate. In Staad foundation we can only consider roof plates, bottom plates, and tank average thickness. But doing that does not get me the actual weight of the storage tank. To consider actual weight I add some loads in Miscellaneous Dead Load (Misc) section (attached picture), but afterward, the results do not change. I have done it for different numbers of load values but it was meaningless, the result did not change. Is there any possible way to consider the weight difference in the Staad foundation to get the actual weight?