Seismic performance of RC frames with masonry infills retrofitted by precast ultra-lightweight insulated cementitious composites plates

This paper presents an investigation on the seismic behavior of RC frames with masonry infills retrofitted by precast Ultra-Lightweight Insulated Cementitious Composites plates under cyclic loading. The objective was to provide an easy retrofit approach for concurrent seismic behavior and energy efficiency upgrading of existing RC frames. Three scaled RC frames were built including a control frame and two frames with different retrofit schemes. The experiments were conducted to investigate the effect of different retrofit schemes over the failure patterns, hysteretic curves, energy dissipation abilities, skeleton curves, and characteristic loads and displacements. The retrofitted RC frames provided higher carrying capacities, energy dissipation abilities, and displacement ductility. Retrofit schemes proposed can prevent severe damage of masonry infills, and alleviate shear failure of columns significantly. Based on the test results, ULICC plates influenced on the flexural moments of columns and beams, and base shear distribution were analyzed. Interactions between retrofitted infills and surrounding frames were discussed. A theoretical model based on equivalent strut was proposed to obtain initial lateral stiffness and carrying capacity of retrofitted RC frames. The experiments have demonstrated that precast ULICC plates retrofit strategy can enhance the seismic performances under low-frequency cyclic loading.