In industrial buildings, the foundation is generally at +0.00. There is soil frost depth according to regions. therefore, it is necessary to lower the foundation a little. at least like 50 cm. again on the ground there is at least 50 cm of vegetable soil at the top. That's why you have to go down. In this case, if you do not change the upper level of the raft to +0.00, the raft will not be of practical use. that is, it does not make sense to bury the foundation and fill it again and make 15-20 cm of ground concrete on top. On the other hand, a column is necessary for load transfer to the foundation. Define columns under the steel columns, such as 50-60 cm in height. superstructure max. have the support effects act on this column. dissolve the system without diaphragm. I usually use a single basis in such structures or a continuous basis for the worse scenario. Choosing a column size (slightly larger) based on the dimensions of the base plate and starting the job will make the job shorter. The attached pictures show the shape of a job that has been done before. If you want detailed information, please write...