Assessment of bond-lengths in the design of pretensioned RC elements

Bond of prestressing tendons plays a crucial role in the design of pretensioned concrete structures, with numerous design verifications based on the assumption of "perfect bond". In common design practice, bond of prestressing tendons is generally considered in terms of transmission and anchorage lengths. In precast practice, a different release methodology is often associated with a different type of precast member. Indeed, the prestress force in hollow core slabs is typically gradually released by sawing through concrete and steel. On the other hand, tendons in long span girders are generally flame cut, resulting in sudden release of prestress. Furthermore, these two types of elements differ for the presence (or absence) of shear reinforcement, thus resulting in different types of verifications. In this work, the design verifications that require the computation of transmission or anchorage length will be performed for some case studies, to assess the impact of the bond lengths computed according to the current norms and a new reliability-based formulation proposed by the authors. Results show that despite the proposed modifications eing substantial in some cases (both in terms of increasing or decreasing onerousness), the impact on the design verifications is most of the time limited