Static Behavior Of Circular Tubed RC Slender Columns With High Longitudinal Reinforcement Ratio

A circular steel tubed reinforced concrete (RC) column with high longitudinalreinforcement ratio (CTRC-HLRR) is a RC column confined with a circular thin-walled steel tube which is disconnected in the beam-column joints. It is a new typeof composite columns that the steel tube doesn’t bear the axial compression directlyand just confine the concrete column effectively in the radial direction.Experimental research and finite element analysis on the circular steel tubed slenderRC columns are conducted to investigate the axial and eccentric compressionbehavior under static axial and eccentric compression respectively. The main workis as follows:Four circular steel tubed RC slender columns under static axial compression and8ones with the same parameters under static eccentric compression are tested. Theexperimental parameters are slenderness ratios (λ=24,40) and eccentricities(e=0mm,25mm,50mm). The section diameters include200mm and240mm. Thelongitudinal reinforcement ratios are6%and4.2%respectively. The tube diameter-to-thickness ratio are134and161respectively.The failure modes, load-carrying capacity, load-midspan displacementcurves, lateral displacement curves along the column, load-stress curves of thesteel tube are obtained from the test. The test results illustrate that the CTRC-HLRRhas a higher ultimate bearing capacity and good ductility. The instability failure ofCTRC-HLRR slender columns under static axial or eccentric compression isextreme value point instability. Slenderness ratio and eccentricity have a greatereffect on the ultimate bearing capacity. With the increase of slenderness ratio andeccentricity, the ultimate bearing capacity of the specimen reduces continuously.The CTRC-HLRR model is developed with the finite element software ABAQUSto analyse the behavior of CTRC-HLRR under static axial and eccentric compression.The finite element results are in good agreement with the experimental data.Based on the finite element model, A parametric analysis is conducted to studythe influence of the slenderness ratio, steel ratio, concrete strength, steel yieldstrength on the behavior of the specimen subjected to axial or eccentric compression.