This paper highlights an ongoing study aimed at investigating the use of strain-hardening, high performance fiber reinforced concrete (HPFRC) materials in the critical regions of coupled walls that laterally brace many structures. During a large earthquake it is anticipated that the coupling beams will undergo significant inelastic deformations and it is important for these beams to have a high energy dissipation capability and good stiffness retention. However, placing the steel reinforcement required in reinforced concrete (RC) coupling beams to resist earthquake-induced deformations is labor intensive and costly, which often leads practicing engineers to discard the use of such coupling beams. The concept behind this study was conceived from the idea that the next generation of RC structures should utilize ductile concrete in critical regions, rather than extensive reinforcement detailing to provide shear resistance and concrete confinement and thus, achieve an increase in deformation capacity and stiffness retention of structural members and systems.
This paper will discuss the observed behavior of precast HPFRC coupling beams, based on results from large-scale reversed cyclic displacement tests of individual coupling beam specimens at the University of Michigan. These test results indicate that HPFRC can be used as a replacement for normal confinement reinforcement, to provide additional shear resistance, and to increase coupling beam damage tolerance.
The next phase of the project will be the testing of four-story coupled wall systems under displacement reversals at the University of Michigan. The design and construction of those specimens, which includes the use of precast coupling beams, is now in progress.
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