Behavior of high-performance fiber-reinforced cementitious composite materials for earthquake-resistant design

Development and modeling of High Performance Fiber-Reinforced Cementitious Composites (HPFRCC) for use in key shear and/or moment regions of damagecritical concrete structural elements is currently being investigated. More specifically, HPFRCC is being explored for use in the coupling beams of coupled shear walls, a popular reinforced concrete (RC) structural system for medium-rise structures in areas of moderate to high seismicity, as well as in the plastic hinging regions of the structural walls themselves. An experimental program has been conducted to further understand the behavior of HPFRCC under general biaxial stress states, such as would be expected at various key locations in a coupling beam. Concrete plate specimens comprising mixes containing from one to two percent volume fraction of hooked steel fibers and Spectra (polyethylene) fibers have been tested. After exploration of these different fiber types and volume fractions, a 1.5 percent volume fraction of hooked steel fibers was selected as the concrete mix for more comprehensive examination. HPFRCC in compression was found to exhibit about 50 percent residual stress up to 0.03 strain, as well as a shift in failure mechanism from tensile splitting to faulting or shear failure. Also the strength envelope shows biaxial compressive strength gains of over 40 percent with the addition of HPFRCC. Using the knowledge and behavioral trends gained from the laboratory tests of these HPFRCC materials, it can be possible to extrapolate their energy dissipating behavior to uses in structural elements for seismic design.