Seismic behavior of confined masonry walls subjected to freeze-thaw cycles

This paper presented a systemic research evaluating the seismic behavior of confined masonry walls subjected to different freeze-thaw cycles (FTC). The seismic behavior of frost-damaged confined masonry walls was related to the mechanical properties of the frost-damaged masonry material. Thus, the mechanical properties of the frost-damaged masonry material were investigated firstly. Then, pseudo-static tests were conducted with four levels of frost-damage on confined masonry wall specimens. The visual damage, failure patterns, hysteresis behavior, bearing and deformation capacity, strength degradation, lateral stiffness degeneration and energy dissipation capacity were analyzed. Results showed that with an increasing number of FTC, the compressive strength, elastic modulus and Poisson's ratio of the masonry material decreased whereas the strain at peak stress increased. Moreover, with an increasing number of FTC, the peak load, strength attenuation coefficient, lateral stiffness and energy dissipation of the specimens gradually decreased whereas the cracking displacement and ultimate displacement gradually increased. After 120 FTC, the peak load were lower by 38.9%, the ultimate displacement increased by 12.4% and the cumulative energy dissipation of the wall specimens decreased by 72.6%. Finally, the formula for shear bearing capacity for confined masonry walls under FTC was derived based on the results of mechanical property and pseudo-static tests.