Seismic risk mitigation of masonry structures by using FRP reinforcement

In this paper the problem of the seismic reliability assessment of ordinary masonry wall systems strengthened with fiber reinforced polymers (FRP) is considered. Recently, the use of these high strength composite materials, like Carbon or Glass fiber composites, has considerably increased in the field of structural repair of both recent and historical masonry buildings. The applications in the field of architectural heritage are mainly intended to prevent the loss of the construction (with its frescoes, ornaments, sculptures), as a result of exceptional actions like earthquake. In case of such events, the net of reinforcing elements must allow the structure to do not collapse. However, the application of FRP external reinforcements with elastic-brittle behavior on low ductility structural elements like masonry walls induces a further reduction of the componential ductility, moving the system toward an ideal elastic-brittle behavior. This involves a careful examination of the brittle components “bundle effect” in order to evaluate the restoration effect on the reliability of the structural system. In fact, the simple evaluation of the safety margin of each structural element does not lead directly to a reliability judgment on the structure as a whole. As is well known, in case of brittle elements, the collapse load of the system can be significantly lower than the sum of the single structural element collapse load.