Masonry arches strengthened with composite unbonded tendons

In this paper an analytical model to evaluate the structural behavior of masonry arches and vaults strengthened with composite unbonded tendons placed at the extrados is presented. The tendons are fixed at the imposts. The model is formulated under the assumption of finite displacements. The displaced equilibrium configurations are identified by the stationariety of the potential of the acting forces. It is shown that when the tendon is not pretensioned an increase of the arch collapse load can be achieved only if the axial stiffness of the tendon is sufficiently large. Instead if the tendon is pretensioned an increase of the load that induces the first displacement of the arch is always achieved. If the stiffness of the tendon is sufficiently large the collapse load will be greater than the load that produces the first displacement of the arch.