Investigation of in-plane seismic retrofit of unreinforced masonry walls by means of vertical steel ties

•Experimental study of seismic retrofit of URM walls using vertical steel ties.•The URM walls consist of solid clay bricks with low shear strength mortar.•The technique shows significant improvement of walls hysteresis behavior in terms of strength.•The proposed technique enhance URM walls ductility. In this paper, a technique for seismic retrofit of unreinforced masonry walls is studied which comprises addition of two vertical steel ties on both edges of the walls. In total, four specimens have been tested under cyclic lateral load in combination with vertical constant load: two specimens with ties and two without ties. The tests show that vertical ties cause significant increase in seismic capacity in terms of both strength and ductility not only at yield but also at maximum. The ties also cause the failure modes to transform from either shear slip or diagonal tension into a combination of diagonal tension and toe-crushing.