Effectiveness of superelastic bars for seismic rehabilitation of clay-unit masonry walls

This paper presents the results on shaking table tests of half-scale brick walls performed to investigate the effectiveness of newly developed Cu-Al-Mn superelastic alloy (SEA) bars in retrofitting of historical masonry constructions. Problems associated with conventional steel reinforcing bars lie in degradation of stiffness and strength, or pinching phenomena, under cyclic loading, and presence of large residual cracks in structures during and after intense earthquakes. This paper attempts to resolve the problems by applying newly developed Cu-Al-Mn SEA bars, characterized by large recovery strain, low material cost, and high machinability, as partial replacements for steel bars. Sets of unreinforced, steel reinforced, and SEA-reinforced specimens are subjected to scaled earthquake excitations in out-of-plane direction. Whereas steel-reinforced specimens showed large residual inclinations, SEA-reinforced specimens resulted in stable rocking response with slight residual inclinations. Corresponding nonlinear finite element (FE) models are developed to simulate the experimental observations. The FE models are further used to examine the sensitivity of the response with respect to the variations in experimental conditions. Both the experimental and numerical results demonstrate the superiority of Cu-Al-Mn SEA bars to conventional steel reinforcing bars in avoiding pinching phenomena.