LATERAL STRENGTH OF STEEL FRAMES WITH MASONRY INFILLS HAVING LARGE OPENINGS

This paper describes an experimental program to investigate the in-pla ne seismic behavior of steel frames with unreinforced masonry infills having large window openings. Test parameters included the masonry pie r width and the number of wythes. Infill strength and stiffness deteri oration seemed to be independent of the pier width or the number of wy thes. Results indicate that the ultimate shear strength of these infil ls ranged between 0.82 and 1.08 MPa (120 and 157 psi). Stiffness deter ioration for each infill was almost identical. By 0.20% drift each inf ill lost more than 70% of its original effective stiffness, with the r emaining stiffness degrading by 2.0% drift, Ductility of these tested masonry infills depended on the pier width and the number of wythes. N arrow piers tended to be more ductile than wide piers, resulting in le ss observable damage in the brick at large-amplitude drifts. Similarly , the double wythe infills tended to be more ductile than single wythe infills. This research was directed toward possible use in the evalua tion methodologies of ATC-33.