Similitude of 1/3 Scale Concrete Masonry Units

Proceedings of the Tenth North American Masonry Conference
St. Louis, Missouri
June 3-6, 2007

Thomas Golecki, Elizabeth Holly, Franklin Moon, and Ahmad Hamid

Due to the highly interconnected and redundant nature of masonry bearing wall structures, there is an increasing recognition that such structures must be viewed as holistic systems as opposed to a combination of fragmented, isolated components. Given that the accurate a priori modeling of such structural systems has proven difficult, there is a need for experiments of complete masonry structures aimed at uncovering system-level mechanisms to allow past component studies to be more effectively leveraged and to identify and affect appropriate code changes. However, the testing of complete structural systems presents multiple problems related to cost and inadequate laboratory size. Faced with these challenges, many past system-level experiments have explored and demonstrated that reduced scale modeling can be a sufficient alternative to full scale testing. In order for a reduced scale model to be useful however, its behavior must first be rigorously shown to be a representative of the corresponding full-scale behavior, termed similitude. Once the similitude of a reduced scale masonry system has been established, scaled structures can be constructed and tested to provide the required insight into system-level behavior. This paper discusses an on-going study aimed at developing 1/3-scale concrete masonry units (CMU) that satisfy similitude requirements, using a reduced scale block making machine recently acquired by Drexel University. This study examined many variables that may affect the mechanical properties of the small-scale units such as aggregate size, mix proportions, compaction pressure, and curing time. The results show that although the geometric properties can be consistently replicated at reduced scale, the mechanical properties are more difficult to attain.

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