Experimental Research On Seismic Behavior Of Tubed Rc Short Columns With High Longitudinal Reinforcement Ratio

A tubed RC column with high longitudinal reinforcement ratio (TRC-HLRR) is a common RC column with high longitudinal reinforcement ratio and the RC column is tubed with a thin steel tube. In this kind of columns, the total steel ratio is close to that of SRC or CFST columns. Tubed RC column with high longitudinal reinforcement ratio is a new type composite column in which the steel tube disconnects in the joint of framework. The tube does not bear axial load directly, only has the effect in confining the core concrete. This kind of columns could effectively simplify the complex form of SRC or CFST column to RC beam connections. Seismic behavior of TRC-HLRR short columns is analyzed theoretically and experimentally in this paper. The main contents are as follows:A total of 4 circular TRC-HLRR short columns and 4 square TRC-HLRR short columns are designed and manufactured. The longitudinal reinforcement ratio of all the specimens is 4%. The test parameter is axial load ratio, shear span to depth ratio and diameter/width to thickness ratio of the tube.The specimens are tested under combined constant axial load and cyclic lateral load. The load-displacement curves and load-strain and curves stress states of mid-span of the tube are obtained during the test. The failure modes, envelopes of the cyclic curve, deformation capacity, ductility performance, energy dissipation ability are analyzed. The test results show that TRC-HLRR short columns exhibited excellent seismic behavior. Even the specimens with the shear span ratio 1.5 occurs shear failure, the elasto-plastic limit inter-story drift ratio meet requirement the specification for RC columns. As axial load ratio increases, bearing capacity of the specimens with shear failure increases, while the ductility decreases as the axial load ratio increases. The ductility of the specimens with flexural failure remains stable as axial load ratio increases.Based on the results from test and analysis, the shear strength formula for tube RC column is proposed, the results from the proposed formula compared well with the test results.