According to Eurocodes, we multiply designed loads by safety factors to account for non idealities and uncertainties. When multiple load types affect a structure, the corrected loads are summed and the sum is multiplied again by a load combination specific factor. Why do we need to correct the sum as well?
For example, we may have a live load and a snow load on a structure. Both have their own safety factors, but why does their combination have one as well? Aren't the uncertainties included already in the individual factors for each load?