Experimental Investigation of Concrete Frames Infilled with rc for Seismic Rehabilitation

New reinforced concrete (RC) walls are popular in seismic rehabilitation of RC buildings as they reduce seismic-deformation demands. Their effectiveness was experimentally investigated by pseudodynamically testing 3∶4 scaled models of three four-story frames infilled with RC. The specimens were considered part of a frame building, the rest of which was substructured in the test as elastic. Unlike in past tests, the wall web was not thinner than the frame members and the specimens were tall enough to be governed by flexure. Two code-conforming designs were tried for the connection of the web to the surrounding frame members, one of them being less labor-intensive. Behavior and failure were dominated by flexure, but open, u-shaped FRP jackets at the two edges of the composite wall were essential to prevent premature failure near the base because of poor detailing of the columns. Slippage/separation at interfaces between the web and surrounding frame members was minor for both connection details. In one specimen the critical plastic hinge did not form at the base but instead in a horizontal band defined by the first-story beam of the frame, in which the vertical beam stirrups were much weaker than the vertical wall reinforcement; however, this did not adversely affect the global energy-dissipation and deformation capacity. The values of the secant-to-yield-point stiffness, yield moment, and ultimate chord rotation of the composite walls inferred from the tests are in good overall agreement with expressions given in international codes for monolithic walls with the same geometry, reinforcement, and detailing.