A Seismic Retrofit for Masonry Infill Walls using Ductile Concrete

Understanding and assessing the seismic performance of masonry infilled reinforced concrete structures has been a significant area of research over the last several decades. There is both field and laboratory evidence of masonry infilled reinforced concrete structures not adequately designed for earthquake loading that demonstrated the catastrophic contribution of the unreinforced masonry infill to the structure due to its interaction with the bounding frame. There is a lack of reliable and effective retrofit techniques for this group of structures. A new retrofit technique specifically for unreinforced masonry infills in non-ductile reinforced concrete frames is currently under investigation. The technique uses a ductile fiber-reinforced mortar material referred to as Engineered Cementitious Composites, or ECC. A series of experiments have been performed in order to examine the impact of a thin layer of ECC applied on masonry alone as well as when it is applied on a masonry wall bounded by a non- ductile reinforced concrete frame. Results indicate that the ECC can help keep unreinforced masonry walls in tact to large lateral drifts, adding significant ductility to the structural system under cyclic loading.