Assessment of high-strength concrete encased steel composite columns subject to axial compression

• Published in: Journal of constructional steel research Vol. 164; p. 105765
• Main Authors: Lai, Binglin, Liew, J.Y. Richard, Venkateshwaran, Akshay, Li, Shan, Xiong, Mingxiang
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.01.2020
• Subjects: Axial capacity; Concrete confinement; Concrete encased steel columns; High strength concrete; High strength steel; Spalling; Spalling; Concrete encased steel columns; Concrete confinement; Axial capacity; High strength concrete; High strength steel
• ISSN: 0143-974X; 1873-5983
• DOI: 10.1016/j.jcsr.2019.105765

This paper investigates the axial load capacity of concrete encased steel composite stub columns with high strength concrete and steel materials. A total of 14 column specimens with varying material strengths and different steel section shapes were tested under concentric compression load. The test results revealed that the design methods in EN 1994-1-1 and JGJ 138-2016 overestimate the axial load capacity of high strength concrete encased steel columns. Adding a small percentage of steel fiber in the high strength concrete was found to improve the compression resistance of the composite section. A new test database consisting of 51 partially encased composite sections and 82 fully encased composite sections was established, covering a wide range of section geometric and material grades. Parametric study was then carried out to assess current design methods in predicting the axial capacity of such composite columns with respect to material strengths, steel contribution ratio, reinforcement ratio, section slenderness ratio, confined concrete area ratio, and concrete confinement efficiency. The effectiveness of concrete confinement in partially encased composite column was evaluated and a simplified method was proposed to compute the enhanced concrete strength based on regression analysis. For fully concrete encased composite columns, a concrete strength reduction factor was proposed to be used with EN 1994-1-1 to predict the compression resistance. Design recommendation was made considering the early cover spalling of high strength concrete and the material compatibility between steel and concrete in composite column design. •Test is performed on CES stub columns with C90/C130 concrete and S500/S690 steel.•A database is collected to perform a comprehensive assessment of current design codes.•A simple equation is proposed to evaluate confining effect of PEC columns.•Design recommendations are proposed for FEC column.