EXPERIMENTAL STUDY ON COMPRESSION BEHAVIOR OF CONCRETE COLUMNS WITH HIGH STRENGTH STEEL BARS UNDER SMALL ECCENTRIC LOADING

To study the compression behavior of high-strength reinforced concrete columns and further promote the application of high-strength reinforcement in concrete structures, six concrete columns reinforced with HTRB630 steel bars were tested under small eccentric compression load. The influence of reinforcement ratio, hoop reinforcement ratio, hoop spacing and load eccentricity are investigated. The failure process, failure modes and deformation capacity of test specimens are analyzed, and the stress level of the steel bars are evaluated. The test results indicate that the HTRB630 steel bar in the compression zone of specimens can reach the yield strength, and the plastic deformation can be fully developed. Increasing the hoop reinforcement ratio can improve the bearing capacity of the specimen under small eccentric compression load. When the hoop reinforcement ratio exceeds 1.50%, the bearing capacity of the specimen is not significantly improved, but the deformation capacity of the specimen can be improved to a certain extent. Considering the confined effect of hoops on concrete, and referring to the calculation method of current Chinese code, a calculation method for determining the bearing capacity of concrete columns under small eccentric load is extended. The calculation results are in good agreement with the experimental results. The method can be used in engineering design and improvement of the specification.