Influence of masonry properties on confinement: a mechanical model

Design provisions for the repair, retrofitting, and rehabilitation of existing masonry structures are not always available and included in International and National Building Codes. Due to the extremely large variability in masonry performances, equations of general validity cannot be provided, namely relationships suitable for confinement of every masonry type, as it is done for concrete. Large amount of results obtained for concrete led to consolidated design guidelines. Despite the great research effort in the experimental field on masonry, considerable theoretical work is still needed to fully outline a definitive analytical model to predict the behavior of FRP confined masonry. In this study, a mechanically based confinement model is proposed based on mechanical parameters able to differentiate similar masonry types and to highlight that they present different confinement performance. The most relevant parameters are the compressive and tensile strength of unconfined masonry and they are discussed in the framework of solid mechanic based models based on triaxial plasticity and calibrated experimentally. The proposed approach can then be extended to other masonry types.