Dynamic testing of unreinforced brick masonry infills

A significant seismic hazard may exist when unreinforced masonry infill panels fall out of their surrounding frames as a result of excessive accelerations applied normal to their plane. The safety of URM infills with respect to out-of-plane loadings can be further aggravated if substantial cracking occurs during previous in-plane loadings. An experimental study is underway at the U.S. Army Construction Engineering Research Laboratories to study the seismic behavior and strength of previously cracked masonry infill panels when subjected to lateral accelerations normal to their plane. Half-scale test specimens consists of single-story, single-bay reinforced concrete frames with single-wythe clay brick infill panels. Test specimens are first subjected to simulated earthquake motions applied parallel with the infill plane to crack the infill panels; then, they are rotated 90 degrees and subjected to out-of-plane accelerations. Test results are reduced in terms of equivalent lateral pressures and lateral drifts for each test panel. Equivalent lateral pressures are calculated based on the recorded lateral accelerations. Laboratory measurements are correlated with test results of a sister research program done at the University of Illinois with similar but full-scale static specimens to discern differences attributable to scale and strain rate. The paper presents a summary of the available experimental work done to date, along with a discussion of their corresponding results, and their correlation to the full-scaled test results.