EXPERIMENTAL CALIBRATION OF THE IP BEHAVIOR OF STRENGTHENED INFILL WALLS AND SEISMIC ANALYSIS INCLUDING IP/OOP EFFECTS

Thin masonry infills, classified as nonstructural elements, and often neglected in design models, strongly influence the seismic behavior of RC frames by increasing the overall structural stiffness; in addition, they can be the cause of brittle failure mechanisms, such as soft-floor mechanisms. Moreover, given their very brittle behavior and high IP/OOP response interaction, they are easily damaged even at low to medium seismic intensities. As a result, they are responsible for the high loss of building functionality and high repair costs. This paper presents several concentrated plasticity models for representing the IP behavior of different reinforced and unreinforced infills, calibrated for four different panels using experimental tests. The objective is to provide simplified models, using a commercial FEA program, to best represent the nonlinear behavior of the infills. After IP calibration of the panels, the seismic analysis of an existing 6-story frame infilled with unreinforced and strengthened panels is presented. The conducted nonlinear dynamic analysis is aimed at estimating the expected annual loss (EAL), according to Italian guidelines, to evaluate the effectiveness of the adopted strengthening solution.