Summary of a Large- and Small-Scale Unreinforced Masonry Infill Test Program

A five-year, large- and small-scale, static and dynamic experimental research program, in which more than 700 tests were conducted, has demonstrated that unreinforced masonry infills are more ductile and resist lateral loads more effectively than anticipated by conventional code procedures. The tests were conducted both in the laboratory and on existing structures at the Department of Energy’s Y-12 National Security Complex. The experimental data indicate that the combination of a steel frame and infill material efficiently resists lateral loads—the infilling provides significant lateral stiffness while the surrounding frame adds ductility and confinement to the overall system. The results from approximately 25 moderate- and full-scale tests on infills showed that with simulated seismic loads the frames confined the masonry, and the load-carrying capacity of the infill was considerably above the load that caused initial cracking. This finding was a significant departure from classical code approaches that assumed first cracking to be failure of an unreinforced masonry wall. The experimental program, performed for the U.S. Department of Energy, consisted of the following large-scale tests on infills: in situ airbag pressure testing, shake-table tests, and the application of quasistatic in-plane and out-of-plane drift loads. In situ and laboratory constitutive property tests were also conducted. This paper provides a summary of the overall experimental methodology and results.