City Research Online

Abstract

In this paper, a new type of composite sections, which are composed of one outer square steel tube, four inner circular or square steel tubes and filled concrete, four-opening concrete filled sandwich steel tube (FCFSST), is first developed. To assess seismic response of typical beam-columns, the tests under axial compression and lateral cyclic loading were conducted on ten FCFSST specimens and one counterpart concrete filled steel tube (CFST) specimen. Effect of several key variables, including void ratio (), axial compression level (), nominal cross-sectional steel ratio () and sectional type of inner tubes, on the seismic performance of representative FCFSST specimens was investigated in detail. The experimental observations show that, the failure modes of FCFSST beam-column specimens include outward local buckling (LB) and fracture following LB of outer tube, inward LB and fracture following LB of inner tubes and crushing/cracking of sandwich concrete, and generally and are the controlling factor for the failure of outer tube, whilst and sectional type mainly affect the failure of inner tubes. For the FCFSST specimens, a lower and a larger result in a superior plumpness of the hysteretic curve, a slower stiffness degradation, a higher energy dissipation, and a better ductility, and the influence of and on key factors is more significant than that of . Additionally, in comparison with the reference CFST specimen, the FCFSST specimens show a 20.8 % increase in lateral capacity, a 5.0–9.5 % increase in cross-sectional flexural stiffness, and a 11.7–21.7 % increase in energy dissipation, while presenting a 22.7–25.2 % reduction in ductility coefficient and an 8.2–20.1 % reduction in ultimate drift, respectively. Finally, the approaches in the existing design specifications of composite structures were used to predict flexural capacity and cross-sectional flexural stiffness of FCFSST beam-columns under lateral cyclic loading, and the results indicate that the approach in T/CCES can precisely and safely predict the flexural capacity by considering the increased steel yield strength under cyclic loading, whereas the approach in AISC can offer an accurate prediction for the cross-sectional flexural stiffness.

Publication Type:	Article
Additional Information:	© 2024. This manuscript version is made available under the CC-BY-NC-ND 4.0 license https://creativecommons.org/licenses/by-nc-nd/4.0/
Publisher Keywords:	Four-opening concrete filled sandwich steel tube (FCFSST), Beam-columns, Lateral cyclic loading, Capacity, Cross-sectional flexural stiffness, Design specification
Subjects:	T Technology > TA Engineering (General). Civil engineering (General) T Technology > TH Building construction
Departments:	School of Science & Technology School of Science & Technology > Engineering
SWORD Depositor:	Symplectic Administrator

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