Estruturas de Betão

“The prestress forces applied to the structures and the structural elements are permanent but are not constant throughout the elements, nor in time. This spatial and temporal variation of pre-effort is called prestress losses. Usually losses are divided into two types: instantaneous and deferred. The instantaneous losses are those that occur at the moment of the application of the load and can happen due to several causes, depending on the type of system used, such as the friction between the armatures and the element, the displacement of the mooring devices of the armatures, the concrete deformation or the temperature decrease. The deferred losses are those that occur due to the variation of the materials’ properties and they happen during the time of construction. The causes for these losses are the concrete’s shrinkage and urgency and the steels’ relaxation.”