Experimental and analytical investigation of out-of-plane and in-plane seismic drift in unreinforced masonry infilled frames

The use of structural steel frames infilled with unreinforced masonry is a common construction technique and has been shown to provide significant strength and ductility for the resistance to lateral loads. The research described herein addresses the effect that prior damage--resulting from seismic drift--has on the stiffness and ultimate capacity of infilled frames. The two-fold objective was (1) to study the out-of-plane and in-plane behavior of unreinforced masonry infills with and without prior damage, and (2) to determine accurate and efficient means of modeling infilled frame behavior.;The experimental phase of the research consisted of (1) out-of-plane testing of a bare frame without infilling, (2) out-of-plane followed by in-plane testing to failure of an infilled frame, and (3) in-plane testing to failure of an undamaged infill. The structural steel frames consisted of W10 x 33 columns and a W16 x 36 purlin. Column spacing was 24 feet and the purlin height was 21 ft - 1 in. The infill material was approximately 13 inches thick and composed of individual four- and eight-inch structural clay tile that alternated position from course to course. In addition to the full-scale testing, numerous correlative tests were performed including mortar cube, mortar cylinder, unit block, prism compression and bond wrench tests as well as out-of-plane modal surveys.;Following the experimental phase of this research, the out-of-plane and in-plane behavior and ultimate capacity were predicted using various analytical techniques. The out-of-plane analysis consisted of a series of piece-wise linear finite element models. This analysis reproduced the maximum tensile and compressive load/deflection behavior within ten percent of the actual test results, and predicted crack patterns were very close to those that resulted from the out-of-plane testing. Four classical methods for the prediction of in-plane damage and ultimate capacity were evaluated based on the test data.