Tensioning Process Update for Cable Stayed Bridges

Construction of cable stayed bridges is very challenging. These structures are extremely redundant and the effect of tensioning one cable has the effect of changing the stresses of the already installed cables. In order to achieve a targeted service state at the end of the construction process careful calculations has to be done by the contractor in order to ensure it. However, deviations arise between the modelling of the tensioning process and the actual results obtained on site. In order to adjust the final stresses in the cables, a final restress of the stays is unusually required. This re-stressing operation is usually done for the whole cable, as the strand by strand stressing technique used for the first stressing operations, cannot be used anymore. This last operation is costly, time consuming and has less accuracy, compared with the strand by strand tensioning techniques. The paper will present a method to control the tensioning process on site and to modify it according to the stresses measured in the cables at each stressing stage. In this way, the chances of requiring a restressing operation are diminished.