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Title: Flexural Testing of Circular Concrete-Filled Tubes without Axial Forces

Author(s): Andrew Nghiem, Thomas H.-K. Kang, Minsun Lee, Chris Ramseyer, and Cheol-Ho Lee

Publication: Structural Journal

Volume: 115

Issue: 2

Appears on pages(s): 511-523

Keywords: circular concrete-filled tube; effective stiffness; end plates; flexural testing; nominal moment strength

DOI: 10.14359/51701134

Date: 3/1/2018

Abstract:
Most prior experimental research on concrete-filled tubes has been focused on concentric or eccentric axial loads. Even though several experimental research programs were conducted without axial forces, those have been done using small-sized specimens. The aim of this study is to examine the flexural behavior of fullscale circular concrete-filled tubes (CCFTs) without axial forces. Additionally, this study investigates the effect of end plates on the flexural behavior. A total of five full-scale beam specimens with typical U.S. steel tubes were tested under four-point bending with a relatively large shear span to examine the flexural behavior of CCFTs including the flexural stiffness and strength. Tests consisted of one hollow thick-walled steel tube, two thick-walled CCFT sections, and two thin-walled CCFT sections. The test results are shown with applied moment, deflection, steel, and concrete strains at each location, and push-out movement of concrete. Furthermore, prior CCFT specimens without axial loads are collectively analyzed to evaluate the nominal flexural strength and stiffness of CCFTs according to ACI, AISC, and Eurocode 4 provisions. The study clarifies that there is no need for code changes regarding the nominal moment strength of CCFTs without axial forces; however, only the ACI 318 code gives reasonable predictions of the flexural stiffness of CCFTs.