Lateral Resistance of Unreinforced Masonry Walls Strengthened With Engineered Cementitious Composite

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Replacement of existing unreinforced masonry (URM) walls, commonly used as a non-structural member in apartments, with new reinforced concrete (RC) components has been used as a reliable method when remodeling is carried out. However, special care needs to be taken when URM walls are removed not to waste construction time and materials. Therefore, retrofitting existing URM walls can be deemed a better solution rather than replacing URM walls with RC ones. Using shotcrete is one of retrofitting techniques of URM walls. However, using normal shotcrete cannot improve adequate ductility and may cause brittle failure at a wall frame or slab connection. Therefore, new materials, such as engineered cementitious composite (ECC) and ultra-high performance concrete (UHPC) have emerged to resolve the problem of normal shotcrete by increasing ductility and toughness of retrofitting materials. In this study, sprayed ECC was used to increase both strength and ductility of existing URM walls. The results of two retrofitted URM walls under lateral quasi-static loading were compared to non-retrofitted one. One strengthened wall, retrofitted masonry wall (RTM)-ECC, was just sprayed and anchored to a wall base. Another strengthened wall, RTM-ECC-WM, was the same as RTM-ECC except for addition of wire mesh. The retrofitted specimens showed significant increase of strength, ductility, and energy dissipation capacity in comparison with the control one. In addition, RTM-ECC-WM indicated higher strength degradation due to the load transferring effect of wire mesh than RTM-ECC.