Strengthening of bridge headstocks with external post-tensioning: design issues and strengthening techniques

There has been a need to strengthen headstocks in bridges due to increased traffic loading and aging bridges. External post-tensioning is a viable solution for such strengthening. While the behaviour of structures strengthening by external post-tensioning for flexure is well understood, there is limited knowledge on the shear strengthening. In this paper, the application of external post-tensioning for shear strengthening of headstocks using conventional prestressing techniques will be discussed. Moreover, an innovative solution developed by the authors using externally prestressed fibre wraps will be presented. Issues related to the effect of existing shear cracks and the importance of repairing such cracks will be discussed, based on the results of model tests on the headstocks in Tenthill Creek Bridge