Structural behavior of arch models strengthened using FRP strips of different lengths

We address structural behavior of masonry arches strengthened through Carbon Fiber Reinforced Polymer (CFRP) strips at intrados or extrados surfaces and subjected to horizontal forces. The paper reports and compares results from experimental tests on 1:2 scale arches and from an analytical model which considers no-tensile strength, infinite rigid, and infinite compressive strength material. Under the assumption that the structure fails due to the formation of a four hinges collapse mechanism, the model allows the calculation of the collapse load and the evaluation of the load-displacement diagram. The model is based on the equilibrium conditions and considers finite displacements. Results provide an evaluation of the dependence of arch structural behavior on the length of CFRP strengthening. In particular the post-peak behavior is evaluated in the perspective of performance based seismic design criteria, which regard the ultimate displacement as a key parameter for seismic capacity. The evaluation shows that, for the considered case study, an increase of intrados reinforcement length produces an increase of maximum load but a decrease of the ultimate displacement.