Bending moments due to permanent loads can be strongly reduced in a generally-shaped structure by introducing a set of additional forces through an external post-tensioning system. The response of these structures under live loads has not been studied yet; therefore, this work investigates the behaviour of these structural systems under load distributions that differ from the permanent ones. First, a definition of a moment-based efficiency is proposed. Next, a parametric analysis is carried out to evaluate the performance of these structural systems by varying the two main design variables and other relevant parameters (strut connection and orientation, discretization, efficiency definition, etc.). Finally, the methodology is applied to a case of study where several post-tensioned alternatives are compared to the standard one (i.e., without post-tensioning) to prove the benefits of adopting external post-tensioning in terms of material-saving.