“…This might be attributed to the cracking of concrete that occurred in experimental analysis which was ignored by idealized FE model during initial loading stages (Ahmed et al, 2019; Guan et al, 2022). Further, quality of concrete compaction, its homogeneity, surface imperfections between the steel tubes and concrete can significantly affect the initial stiffness of the specimens which was not taken care by the simplified FE model (Ghannam and Metwally, 2020; Rizwan et al, 2021). Also, the material models, boundary conditions, which were defined in FE model were represent the ideal behavior, however, in actual practice the material behavior may dilate from this resulting in variation in the results (Liang et al, 2019).…”
Section: Finite Element Analysismentioning
confidence: 99%
“…The contact pressure was improved by 12.1%, 31.3%, and 68.5% in case when orbicular anchorage was provided at L/5, L/4, and L/3 in contrast to specimen without any orbicular rings. Better contact pressure signifies better interaction between steel tube and concrete surfaces (Alatshan et al, 2020; Ghannam and Metwally, 2020). Placing the orbicular rings at L/3 distance can better enhance the composite interconnection between steel tube and concrete surfaces.Figure 22.Variation of contact stress w.r.t.…”
Section: Parametric Investigationmentioning
confidence: 99%
“…The specimen stiffened with internal rings and bar stiffeners enhanced the bond behavior, and bearing ability and lessen the local buckling in the column. However, shear studs seemed to provide lesser shear resistance than bar stiffeners and internal rings (Ghannam and Metwally, 2020;Ekmekyapar, 2019, 2021). Further, the impact of shear studs on flexural behavior was examined.…”
Double-skin tube column sections have been used extensively in recent years. These sections are composed of two adjacent, coaxially spaced steel casings, and the space in the middle of them is occupied with concrete. These CFDST columns behave similarly to CFST sections but are more rigid and have a lesser self-weight. The behavior of a novel type of CFDST column, the orbicular anchored CFDST column, was assessed under axial compression in the current research. It comprises an inside and an outside steel tube with orbicular rings near the ends of the columns. The orbicular rings were positioned at various spots such as [Formula: see text] and [Formula: see text] and a wide range of tests were accomplished to evaluate the functionality of orbicular anchored CFDST columns in respect of maximum load-bearing capability, load-strain behavior, and load-deformation behavior. A FE model was developed and its accuracy was authenticated by comparing its findings with experimental results. Furthermore, a parametric investigation was carried out employing the authenticated FE model to examine the functioning of the proposed CFDST to variations in orbicular position, cross-sectional dimensions of rings, yield strength of orbicular ring, etc. The outcomes of the study indicated that orbicular anchored CFDST columns had 15% higher ultimate load capacity than unstiffened counterparts. The orbicular anchorage improved the ductile response and increased the axial stiffness of the CFDST column. Further, it was concluded that orbicular rings enhanced the constraining effect of external steel casing on sandwiched concrete and improved the composite action of CFDST specimens. The design formula to ascertain the load-bearing ability of columns was also developed and can be employed amid preliminary designs of proposed column sections.
“…This might be attributed to the cracking of concrete that occurred in experimental analysis which was ignored by idealized FE model during initial loading stages (Ahmed et al, 2019; Guan et al, 2022). Further, quality of concrete compaction, its homogeneity, surface imperfections between the steel tubes and concrete can significantly affect the initial stiffness of the specimens which was not taken care by the simplified FE model (Ghannam and Metwally, 2020; Rizwan et al, 2021). Also, the material models, boundary conditions, which were defined in FE model were represent the ideal behavior, however, in actual practice the material behavior may dilate from this resulting in variation in the results (Liang et al, 2019).…”
Section: Finite Element Analysismentioning
confidence: 99%
“…The contact pressure was improved by 12.1%, 31.3%, and 68.5% in case when orbicular anchorage was provided at L/5, L/4, and L/3 in contrast to specimen without any orbicular rings. Better contact pressure signifies better interaction between steel tube and concrete surfaces (Alatshan et al, 2020; Ghannam and Metwally, 2020). Placing the orbicular rings at L/3 distance can better enhance the composite interconnection between steel tube and concrete surfaces.Figure 22.Variation of contact stress w.r.t.…”
Section: Parametric Investigationmentioning
confidence: 99%
“…The specimen stiffened with internal rings and bar stiffeners enhanced the bond behavior, and bearing ability and lessen the local buckling in the column. However, shear studs seemed to provide lesser shear resistance than bar stiffeners and internal rings (Ghannam and Metwally, 2020;Ekmekyapar, 2019, 2021). Further, the impact of shear studs on flexural behavior was examined.…”
Double-skin tube column sections have been used extensively in recent years. These sections are composed of two adjacent, coaxially spaced steel casings, and the space in the middle of them is occupied with concrete. These CFDST columns behave similarly to CFST sections but are more rigid and have a lesser self-weight. The behavior of a novel type of CFDST column, the orbicular anchored CFDST column, was assessed under axial compression in the current research. It comprises an inside and an outside steel tube with orbicular rings near the ends of the columns. The orbicular rings were positioned at various spots such as [Formula: see text] and [Formula: see text] and a wide range of tests were accomplished to evaluate the functionality of orbicular anchored CFDST columns in respect of maximum load-bearing capability, load-strain behavior, and load-deformation behavior. A FE model was developed and its accuracy was authenticated by comparing its findings with experimental results. Furthermore, a parametric investigation was carried out employing the authenticated FE model to examine the functioning of the proposed CFDST to variations in orbicular position, cross-sectional dimensions of rings, yield strength of orbicular ring, etc. The outcomes of the study indicated that orbicular anchored CFDST columns had 15% higher ultimate load capacity than unstiffened counterparts. The orbicular anchorage improved the ductile response and increased the axial stiffness of the CFDST column. Further, it was concluded that orbicular rings enhanced the constraining effect of external steel casing on sandwiched concrete and improved the composite action of CFDST specimens. The design formula to ascertain the load-bearing ability of columns was also developed and can be employed amid preliminary designs of proposed column sections.
“…34 Ghannam and Metwally studied the influence of rectangular, T-shaped, and bar stiffeners on the performance of CFDST specimen subjected to concentric loading using FEM analysis by ABAQUS. 35 Use of stiffeners results in 15% increase in load capacity of CFDST column. The authors recommend the use of R or rectangular stiffeners as these are easy to install and results in similar improvements as provided by T-shaped stiffeners.…”
Section: Introductionmentioning
confidence: 99%
“…The use of longitudinal stiffeners results in increase in ductility and reduction of local buckling of the steel casing 34 . Ghannam and Metwally studied the influence of rectangular, T‐shaped, and bar stiffeners on the performance of CFDST specimen subjected to concentric loading using FEM analysis by ABAQUS 35 . Use of stiffeners results in 15% increase in load capacity of CFDST column.…”
Since recent years, double‐skin tube column sections formed from two parallel, concentrically spaced steel casings, with the sandwiched area between the casings packed with concrete infill, have been employed extensively. The cross‐sectional shapes of the inner and outer casings might be the same or different, such as round, square, octagonal, etc. These concrete‐filled double‐skin steel tubular (CFDST) columns act similarly to concrete‐filled steel tubular (CFST) sections but have less self‐weight and better stiffness. The present study evaluated the response of CFDST column stiffened with orbicular rings under axial compression. It consists of inner and outer steel tubes stiffened by orbicular rings near both ends of columns. The orbicular rings were provided at different locations as L/3, L/4, and L/5, and a series of tests were conducted to obtain the performance of CFDST columns stiffened with orbicular rings with regard to the maximum load‐carrying capacity, load–strain behavior, and load‐deformation behavior. Furthermore, a parametric study was conducted by varying the diameter to thickness ratio, hollowness ratio, the thickness of orbicular rings, yield strength, and location of orbicular rings. The results showed that CFDST column stiffened with orbicular rings have higher ultimate load capacity than unstiffened CFDST. Stiffened CFDST with orbicular rings showed more ductile response than CFDST column and helps to improve the outer steel tube's restraint on sandwiched concrete. In order to estimate the load‐bearing capacity of CFDST columns stiffened with orbicular rings under axial compression, an empirical equation was proposed. The experimental results and findings of the suggested equations were found to be in good agreement.
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