Distinct element modeling of the in‐plane response of a steel‐framed retrofit solution for URM structures

This paper presents the results of a numerical study aimed at assessing effectiveness an innovative steel modular retrofit system on improving in-plane lateral capacity unreinforced masonry (URM) load-bearing structures. The investigated solution consists frames fastened to external surface piers through chemical anchors. Distinct element models are built and calibrated against experimental data coming from series quasi-static tests performed in both bare retrofitted conditions. Two different typologies considered herein: one made up with solid clay bricks lime mortar, assembled header bond pattern, other typical Italian hollow units cement-lime arranged Flemish pattern. A simplified microscale approach, combined mesh-refinement strategy, is adopted decrease computational demand without losing accuracy. All failure mechanisms, such as mortar unit tensile failures, well crushing for high compressive stresses, included developed models. Moreover, methodology explicitly account contribution distinct method (DEM) framework presented discussed. proposed modeling strategy yielded good prediction terms stiffness, strength, hysteretic response, crack pattern strengthened specimens. novel set metrics quantitatively assess performance benefits.