Hernandez-Figueirido, Romero, Bonet, Montalvá
49 rectangular and square columns filled with high strength concrete were subjected to axial loading and a bending moment in order to see the effects of slenderness and variable curvature..
Experimental Study, Results, and Discussions
This research paper studied rectangular and square tubular columns subjected to axial loading and non-constant bending moment distribution. Testing parameters included the length of the cross-section aspect ratio (square or rectangular), wall thickness, and ratio of the top and bottom first-order eccentricity. The paper begins with a review of previous experimental results involving slender rectangular CFT columns that concluded failure is governed by flexural rigidity, thus the strength of the concrete has little impact on its ultimate capacity. For the investigation, 49 tests were performed on HSC-filled columns. The specimens were fixed and eccentrically loaded at both ends following design loads from Eurocode 4 and AISC 360-10; special assemblies were built to maintain the pinned ends of the specimen in the horizontal position. For some, it resulted in the same load, creating constant curvature, however for the remaining samples a non-constant bending moment was presented. From the investigation, it is found that when the eccentricity at the bottom is reduced, the maximum axial load increases since the second-order bending moment is reduced. For the slender specimens of the investigation, the design codes have a 4% error, indicating they are applicable to HSC. However, some cases in AISC 360-10 display unsafe errors, corresponding to cases where second-order effects are related to an overestimation of the flexural stiffness.
Reference
Hernández-Figueirido, D., et al. “Influence of slenderness on high-strength rectangular concrete-filled tubular columns with axial load and Nonconstant bending moment.” Journal of Structural Engineering, vol. 138, no. 12, 2012, pp. 1436–1445, https://doi.org/10.1061/(asce)st.1943-541x.0000590.