BEHAVIOR OF HIGH-PERFORMANCE FIBER-REINFORCED CEMENTITIOUS COMPOSITES FOR RC COUPLING BEAMS IN EARTHQUAKE-RESISTANT STRUCTURAL WALL SYSTEMS

摘要

Coupled shear walls are a popular reinforced concrete (RC) structural system for medium-rise structures in areas of moderate to high seismicity. Since current building code specifications for RC coupling beams typically require substantial longitudinal, transverse, and sometimes even confined diagonal reinforcement, the result can often be reinforcement congestion accompanied by costly operations and time delays. As a design alternative, use of High Performance Fiber Reinforced Cementitious Composites (HPFRCC) has been considered. Use of HPFRCC may allow for a simplified reinforcement detailing, especially when located in critical shear and/or moment regions where extensive reinforcement is usually required. It is expected that the use of HPFRCC can increase coupling beam damage tolerance through a ductile response obtained by the tensile strain-hardening and confined compressive behavior of the material. Additionally, HPFRCC is being investigated as a replacement for some steel confinement reinforcement and to provide an additional shear resistance mechanism. The reported experimental program at the University of Illinois has been conducted to further understand the behavior of HPFRCC under general uniaxial and 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 were tested. Using the knowledge and behavioral trends gained through laboratory tests of these HPFRCC materials, it may be possible to extrapolate the energy dissipating behavior of HPFRCC to potential uses in structural elements for seismic design.