STUDY AND DESIGN OF ANCHORAGE CORNER BLISTERS OF POST-TENSIONING TENDONS

The anchorage corner blisters of internal continuity post-tensioning tendons of bridges built with the cantilever method are singular zones where the simplified formulas for the design of the reinforcement required to resist transverse tensile forces due to the application of point loads, proposed by the current standards, are not sufficient as they do not cover all the effects that require reinforcement. Besides being eccentric and intermediate anchorages, as the anchorages are located in blisters, there is the need to transfer the prestressing force to the bottom slab and web of the girder.
In addition to the difficulties in design, during construction the high density of steel reinforcement in anchorage blisters is often responsible for the existence of zones with low concrete compacity, which may lead to concrete crushing failures under the anchor plates. To reduce the density of steel reinforcement, in
the research project which is the basis of this paper a high-performance fibre reinforced self-compacting mixture (HPFRC) was used
An experimental program was carried out to study the transmission of prestressing force to the slab and web of the box girder, assess the strut-and-tie models used in design and to study the feasibility of using a high performance fiber reinforced self-compacting mixture (HPFRC) only in the blister.
It can be concluded that the use of HPFRC in anchorage blisters is a very interesting solution regarding the saving in materials and the reduction of the steel reinforcement density near the local anchorage zone.