| Summary: | 碩士 === 國立臺灣大學 === 土木工程學研究所 === 101 === From 1988 to 1992, the Japanese government carried on a five-year national project, New RC Project, to substantially increase the strength of the construction materials of the reinforced concrete for high rise buildings. The concrete strength rises from 40 MPa to 120 MPa, and the yielding strength of steel bar rises from 420 MPa to 685 MPa. Up to 2007, there are more than 500 New RC buildings in Japan.
Due to brittleness of high strength concrete, much more confinement is needed to improve the ductility and satisfy seismic requirements for high strength reinforced concrete column, particularly under high axial loading demands. Furthermore, early cover spalling trigs substantial compressive strength loss and thus sudden failure occurs. Many studies show that addition of steel fibers can not only effectively prevent the early cover spalling, but also increase the toughness and ductility of high-strength concrete.
The compressive behavior and confinement effect of high strength steel fiber reinforced concrete columns are investigated in this study. Regression relationships of toughness ratios and fiber/transverse reinforcement parameters are conducted based on the past experimental results. Nine high strength steel fiber reinforced concrete columns (200×200×900mm) were designed with the same toughness ratio to verify the validity and reliability of the proposed formulas. The results indicate that additions of steel fiber not only avoid the premature concrete cover spalling, but also increase the ultimate axial capacity. It is also found that the predicted toughness ratios obtained from the proposed equation have a good agreement with those got from the tests.
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