Hewes, Joshua1 and Brumit, Tyler2
1 Associate Professor, Northern Arizona University, PO Box 15600, Flagstaff, AZ, USA, Joshua.hewes@nau.edu
2 Field Engineer, CB&I, 1051 Alder Way Unit 411, Evans, GA, USA, tyler.brumit76@gmail.com
ABSTRACT
Design of reinforced concrete masonry shear walls for seismic loading is constrained by maximum flexural reinforcement limits of the MSJC Code and by Code requirements for wall boundary
elements. These provisions are written to ensure that walls loaded in-plane can attain the minimum levels of ductility during a seismic event implied by Code R values, and are directly related to the ultimate masonry compression strain capacity, mu. Whereas previous researchers have utilized confinement plates or combs to increase the masonry ultimate compression strain, this research aims to develop a new type of ductile concrete masonry containing randomly distributed fibers in both the grout and masonry units. Inclusion of fiber reinforcement within the grout and block mixes can potentially improve the tensile behavior of the materials thereby increasing the compression strain capacity of the composite masonry material. Consequently, reinforcement limits could be increased while maintaining the same level of curvature ductility capacity. As part of a pilot study, experimental axial compression tests on fiber reinforced concrete masonry units(FRCMU) containing synthetic polymer macro fibers at volume percentages of 0.0%, 0.10%, 0.20%, 0.25%, and 0.50% were conducted and it was found that significant improvements in both pre- and post-peak response can be achieved with addition of the fibers to the block mix. Compression tests on 18, three course tall CMU prisms were also conducted. Six ungrouted prisms were tested, where randomly distributed reinforcement in the FRCMU consisted of synthetic polymers at volume percentages of 0%, 0.10%, and 0.25%. Twelve fully grouted prisms with fiber reinforced grout (FRG) and traditional CMU were tested with both synthetic and steel fiber reinforcements at 1.0% by volume. Prism test results showed a general improvement in stress – strain falling branch characteristics when fiber is present, and pilot study results considered in whole indicate that further study of fiber reinforced concrete masonry is warranted.
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