Behavior of Splicing GFRP-Concrete-Steel Double-Skin Tubular Columns Subject to Eccentric Compression

This paper designs the splicing GFRP-concrete-steel double-skin tubular column (DSTC) specimens based on steel bar connection, and the mechanical performance under eccentric compression load is investigated. The test parameters include the axial connection steel ratio, the load eccentricity and the hollow ratio. The results show that the splicing DSTCs present ductile failure under eccentric load, with the average deflection ductility coefficient of 4.21 and the axial shortening of more than 2% of the column height. The arranged connection steel cage prevents the joint failure, and the columns fail at the non-joint section, characterized by hoop rupture of the GFRP tube and concrete crushing at the same position. The proposed splice method satisfies the strength requirements, with more than 20% increase in the ultimate load compared with the continuous specimen, while the bearing capacity dose not increase with the increase of the axial connection steel ratio. Thus, it is suggested that the low axial steel ratio of 2.44% is used for the splicing DSTCs under relative small eccentricity (20 mm). The ultimate load decreases by about 25% with every 20 mm increase in load eccentricity, and the 40 mm eccentricity causes almost 50% reduction in the initial stiffness and doubles the lateral deflection compared with the axial compression member. The increase of hollow ratio decreases the ultimate load, the initial axial stiffness and also the ductility of the column. The theoretical calculation method for predicting the bearing capacity of the splicing DSTCs is experimentally verified.

Automated summary

This study investigates the mechanical performance of GFRP-concrete-steel double-skin tubular columns under eccentric compression load with a specific splice method, showing ductile failure and prevention of joint failure with arranged connection steel cage. The proposed splice method satisfies strength requirements and can increase ultimate load by more than 20%, while the increase of load eccentricity and hollow ratio decreases ultimate load, initial stiffness, and ductility of the column. The experimental verification of the theoretical calculation method demonstrates its accuracy in predicting the bearing capacity of the splicing DSTCs.