In this work, we are interested in estimating the uncertainty that a system will work, given the probabilities that its components will be either failing or working. Usually, this estimation is done by propagating the component uncertainties through a structure function. This problem is well-studied when component probabilities are known and when the component are assumed to be independent. In this paper, we first recall some results obtained when considering that probabilities are unknown and when it is assumed that components are independent or that no knowledge about the components dependence is available. We also explore some structures not studied up to now, such as consecutive k-out-of-n structures.