Study of unreinforced masonry elements strengthened with engineered cementitious composites under impact loading

Given the brittle behavior and low flexibility of unreinforced masonry walls, using flexible fiber-reinforced concretes, such as engineered cementitious composites (ECCs), to retrofit them is of great importance. In this regard, the performance of these materials (as a reinforcement layer of unreinforced masonry walls) in improving their behavior (flexibility and strength) against dynamic loads, especially impact loads, should be taken into account. The present study evaluates and compares the vertical middle displacement, energy, and distribution of plastic strains in unreinforced masonry materials, under two conditions, i.e., non-retrofitted and retrofitted with a one-side cover (in the lower surface of the specimen) or two-side cover of ECC layers under dynamic impact loading, through nonlinear dynamic impact analysis. The ECC reinforcement layers in two-side covers were investigated by changing their location (in the middle or edges of the lower surfaces of the specimen), connection type (disconnection or full connection) of the one-side cover of the bottom of the specimen with the ECC reinforcement layer and elastic modulus (from 15 GPa to 22.5 GPa). The retrofitting of the unreinforced masonry materials with ECC layers (especially with two-side cover) improved their behavior against out-plane impact loads, dissipated energy, and reduced the plastic strains and cracks.