Evaluation of the infill influence on the elastic period of existing RC frames

• The influence of infills on elastic period of RC frames has been studied.
• A relationship to evaluate the period of infilled RC frames has been proposed.
• The influence of mechanical properties of masonry infills has been considered.
• A linear correlation between period and height of frames has been observed.

The common practice in civil engineering considers the infill as nonstructural elements, thus they are often neglected in the evaluation of the structural seismic behavior. However, the damages observed in past earthquakes around the world, have shown as the presence of infills significantly influence the seismic performance of Reinforced Concrete (RC) resisting frames.Several studies conducted in the last years emphasize the importance of infills on the evaluation of the elastic period of infilled frames; however the influence of mechanical properties of infills walls is often neglected.In this study the effect of infills in the seismic behavior of R.C. frames has been analyzed in terms of modal properties, namely evaluating the elastic period by means an eigenvalue analysis on 2D models. A parametric analysis has been performed taking into account the height of frames, the presence of flat/deep beams, the influence of infills Young modulus and the percentage of openings in the infills. Also the presence of setbacks in the frames has been considered. The numerical results provided useful information about the influence of masonry infill properties and allowed to define a new relationship to evaluate the elastic period of vibration.