Study On Limited Value Of Axial Compression Ratio Of Steel Reinforced High Strength Concrete Column

Steel Reinforced Concrete Structure is composite structure which Reinforced Concrete embraces steel and Steel Reinforced high-strength Concrete is a combination of steel and high-strength concrete. It is a new way for development of steel structures and concrete structures. Steel Reinforced High strength Concrete structure not only has a lot of merits of steel reinforced concrete such as:high load-bearing capacity, big stiffness, good resisting seismic, good ductility, good fire resistance but also effectively reduces member cross-section to improve load-bearing capacity. Especially, with the development of high rise building and the super tall building in modern construction, the columns in the basement bear huge axial compression, if the high-strength rein-forced concrete columns are still applied in the high-rise building, it will not only affect the columns'function, but also shape short column whose seismic behavior is poor, for Limiteds of axial compression ratio will increase the sectional dimensions of columns. It is well known through lots of experiments that steel reinforced concrete columns can effectively reduce the axial compression ratio of the concrete in the columns and im-prove the seismic behavior of the columns because the steel skeleton in the columns can share part of the axial compression. As a result, reinforced high concrete columns, es-pecially for the steel high-strength reinforced concrete columns, are applied widely in modern construction. Through repeatedly horizontal load tests, it is shown that axial compression ratio is an important target that affects seismic behavior of steel high-strength reinforced concrete columns, ductility and seismic behavior of columns will step down to a certain degree when testing axial compression ratio is high. There-fore, the axial compression ratio must be closely restricted in practical engineering in order to ensure seismic ductility of the columns reaching the required standard.Failure patterns, hysteretic curves, skeleton curves, ductile coefficients, energy dissipation,strength degeneration and bond stress degeneration of steel reinforced high strength concrete columns are obtained by conducting tests of 4 specimens with con-crete strength varies from 77.3MPa to 82.5MPa under low cyclic reversed loading and contrast to 3 specimens with concrete strength varies from 69.9MPa to 73.2MPa which were tested under the same condition, then the influences of axial compression ratio on the seismic performance of steel reinforced high strength concrete columns are also analyzed. Finally the recommended limited value of axial compression ratio of steel re- inforced concrete columns with concrete strength grades C65～C80 is determined based on the test results, which satisfies certain requirements of ductility.