Masonry Walls Retrofitted with Vertical FRP Rebars

The out-of-plane behaviour of the walls as a consequence of an earthquake is the main vulnerability of existing masonry structures. In the case of rigid in compression not tensile resistant material, incremental dynamic analyses may be employed to evaluate the effective strength of a rocking element. When the seismic capacity of the wall is inadequate, retrofit interventions are required to assure an acceptable safety level. Conventional seismic retrofitting techniques on masonry walls influence the seismic performance of the element, which typically is modified in an out-of-plane bending behaviour. In this paper, analytical investigations are presented to investigate the possibility of a seismic retrofitting intervention able to increase the seismic strength of the wall without modifying its seismic behaviour. The analysed retrofitting technique consists in the application of composite vertical bars either in the middle section of the wall or at its external surfaces. The seismic behaviour of the retrofitted masonry wall is analytically evaluated by means of a parametric incremental dynamic analysis, carried out with an ad hoc in-house software. The effectiveness of the intervention is analysed in terms of level of seismic improvement, defined as the ratio between the seismic capacity of the reinforced and unreinforced walls.