Under what situation shall engineers use jacking at one end only and from both ends in prepossessing work?

stressing at one end only has the potential advantage of lower cost when compared with stressing from both ends.
For multiple spans (e.g.
two spans) with unequal span length, jacking is usually carried out at the end of the longer span so as to provide a higher prestress force at the location of maximum positive moment.
On the contrary, jacking from the end of the shorter span would be conducted if the negative moment at the intermediate support controls the prestress force.
However, if the total span length is sufficiently long, jacking from both ends should be considered.