Experimental Study On The Compression-bending Behavior Of Assembled Coupled Concrete Filled Steel Tubular Column

Coupled concrete filled square steel tubular column is a new type of assembled composite structure composed of two square concrete-filled steel tubular columns and connectors connected by unilateral bolts.In this paper,the compression and bending performance test and finite element numerical analysis of coupled concrete filled square steel tubular column are carried out,and the whole process of loading of the specimen is studied.The concrete contents are as follows:(1)The compression-bending tests of six coupled concrete filled square steel tubular column were carried out.The effects of eccentricity and number of connections on ultimate load-bearing capacity were studied.The failure modes,load-column deflection curves,lateral deflection curves and longitudinal strain of steel tube surface were analyzed.The test results showed that the coupled concrete filled square steel tubular column experienced elastic and elastic-plastic sections.The ultimate load-carrying capacity of concrete-filled square steel tubular composite columns decreases by 18% when eccentricity increases from 0.2 to 0.4;the ultimate load-carrying capacity of specimens decreases by only 1.7% when the number of connections decreases from 2 to 1;during the loading process,the near-load side columns are kept under full-section compression,while the far-load side columns are developed from small eccentric compression to large eccentric compression.The ultimate failure of the specimens is controlled by the strength of the near-load side columns.(2)A formula for calculating eccentric reduction coefficient of coupled concrete filled square steel tubular column is derived,and the reliability of the formula is verified by experimental data.(3)Applying ABAQUS finite element software,the finite element model of coupled concrete filled square steel tubular column under eccentric load is established.The variation law of load of steel tube and concrete filled in the left and right columns during loading is analyzed.With the increase of eccentricity,the bearing capacity ofnear-load side steel tube and inner-filled concrete remains basically unchanged,while that of far-load side steel tube and inner-filled concrete decreases continuously.Under the same eccentricity,the number of joints decreases and the ultimate bearing capacity of specimens is lower.Limited bearing capacity is low.