Strength and Stiffness of Masonry-Infilled Frames with Central Openings Based on Experimental Results

An extensive statistical analysis is conducted on experimental data to achieve a formula for the strength and stiffness of masonry-infilled frames having central openings. For this, most of the available experimental data were collected and categorized based on their confining frames and opening types. The reliability of existing empirical relations was investigated, in which a reduction factor was suggested that shows the ratio of strength or stiffness of perforated infill to a similar solid one. The study shows that the relation recommended by the literature is the most accurate, among others, to estimate the lateral strength and stiffness of perforated infilled frames. Modified formulas derived from trend analysis of collected experimental data were proposed to determine the mechanical properties of perforated infilled frames. It is also shown that the reduction factor of the ultimate strength of infilled frames caused by the presence of openings depends highly on the material of the confining frames ( steel or concrete), but the reduction factor of stiffness is not affected by the frame type. Therefore, different equations are proposed for the strength and stiffness of infills with openings. (C) 2013 American Society of Civil Engineers.