Modelling of FRP-Strengthened Masonry Buildings with Equivalent Frame Models

Existing masonry buildings can be strengthened to reduce their seismic vulnerability. While the effect of strengthening on the structural elements of a building has been well researched, there are few computationally efficient numerical modelling approaches that capture the effect of strengthening interventions. This paper shows how a recently developed macro-element for unreinforced masonry walls, which can capture both in-plane and out-of-plane failure modes, can model the effect of fibre-reinforced polymer (FRP) strengthening on masonry walls. Practically, FRP strengthening increases the flexural in-plane and out-of-plane strength through longitudinal FRP strips placed against the masonry. In the macro-element, this is modelled through adding fibres to the section model that represent the longitudinal FRP strips. Transversal FRP strips affect the shear strength and in the macro-element this is accounted for by increasing the cohesion in the equation for the shear strength of the macro-element. This paper models quasi-static and dynamic in-plane shear–compression tests as well as out-of-plane bending tests on walls with and without FRP strengthening and compares the numerical simulations to experimental results taken from the literature. The proposed modelling approach for FRP-strengthened masonry walls accurately predicts their in-plane and out-of-plane response, indicating that equivalent frame models can be used to predict the response of masonry buildings with FRP-strengthened walls. The application of the approach is illustrated through hypothetical retrofit configurations of a masonry building that was tested on a shake table in its unstrengthened state.