Abstract
In order to investigate the bond behavior of preplaced aggregate concrete-filled steel tube (CFT-PAC) columns and the difference of bond behavior between CFT-PAC columns and normal concrete-filled steel tube (CFT-NC) columns, a total of 11 columns were prepared and the push-out tests were conducted. The experimental parameters included the type of concrete (preplaced aggregate concrete and normal concrete), concrete strength (C40, C50 and C60), cross-section dimension (D = 219 mm, 299 mm and 351 mm) and the thickness of steel tube (t = 6 mm and 8 mm). The results indicated that the CTF-PAC columns had a similar load-slip curves with CFT-NC columns. The bond stresses of the CFT-PAC columns were higher than that of the PAC-NC columns at the same concrete strength. Increasing compressive strength of PAC increased the critical bond strength and bond strength of CFT-PAC columns. With an increase of the L/D ratio, both of the slip corresponding to peak load and bond strength of CFT-PAC columns exhibited an increasing trend. A rise in the D/t ratio led to a decrease in the bond stress of CFT-PAC columns and an increase in slip corresponding to the peak load of CFT-PAC columns. The proposed bond stress–slip relationship model considerably matched the bond stress–slip relationship of CFT-PAC columns.
Highlights
The concrete–filled steel tube (CFT) structure is one of the types of structures which is comprised of core concrete and steel tube
A similar failure mode between different specimens indicated that the structural parameters had small effect on the failure modes of CFT-Preplaced aggregate concrete (PAC) and CFT-normal concrete (NC)
After bond-slip tests, the core concrete was removed from the steel tube
Summary
The concrete–filled steel tube (CFT) structure is one of the types of structures which is comprised of core concrete and steel tube. Due to the special construction technology, the constraint effect of core concrete by steel tube and the cooperative work between the core concrete and steel tube will be achieved [1,2]. This structure has plenty of virtues in terms of greater carrying capacity, higher lateral stiffness, better ductility properties, much more efficient construction and easier fabricated construction [3,4,5,6,7]. Numerous different types of concrete have been used in concrete-filled steel tubes, such as lightweight aggregate concrete [25,26], high-strength concrete [27], recycled aggregate concrete [28,29,30,31,32] and fiber-reinforced plastic (FRP)-confined concrete [33,34]
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