Experimental study on concrete filled elliptical/oval steel tubular stub columns under compression

doi:10.1016/j.tws.2014.01.023

Thin-Walled Structures

Volume 78, May 2014, Pages 131-137

https://doi.org/10.1016/j.tws.2014.01.023 Get rights and content

Highlights

•
Mechanical behavior of CFEST stub column under compression is provided.
•
Effect of diameter-to-thickness ratios on axially loading capacities is provided.
•
Stress histories of the elliptical/oval steel tubes are described.
•
Method to predict axially loading capacities of CFEST stub column is discussed.

Abstract

A concrete filled elliptical/oval steel tubular (CFEST) member consists of elliptical/oval steel tube and in-filled concrete. The CFEST member is a new type of steel–concrete composite member and is part of a family of concrete filled steel tubular members known as CFT. The present study aims to investigate, experimentally, the characteristics of CFEST stub columns under centric loading. The main test parameters selected are diameter-to-thickness and diameters ratios of elliptical/oval steel tube. From the results, local buckling of the elliptical/oval steel tube associated with shear failure of in-filled concrete could be observed. Axial loading capacity decreased as diameter-to-thickness ratio increased. Whereas, those capacities normalized by the summation of the individual strengths, namely the elliptical/oval steel tube and in-filled concrete strengths, are regulated in case the diameter-to-thickness ratio becomes larger. Finally, a method to predict the axial loading capacity induced by confinement effects of the in-filled concrete is proposed.

Introduction

Concrete filled elliptical/oval steel tubular (CFEST) members consist of elliptical/oval steel tube and in-filled concrete, as shown in Fig. 1. The CFEST is a new steel–concrete composite column structural member and is part of a family of concrete filled steel tubular members, the so-called CFT [1], which have good deformability and large toughness due to the effects of the confinement stresses between the steel tube and the in-filled concrete. Furthermore, when CFEST member is applied to a steel–concrete composite bridge pier located in a river, reduction of the river scouring can be expected owing to the smooth flow of the water in the riverbed.

Tracing the history of the studies on elliptical/oval hollow steel tubes with or without in-filled concrete, various mechanical investigations of CFEST, elliptical hollow steel tubes (EHS) and oval hollow steel tubes (OHS), in which the diameter-to-thickness ratio ranges from 28 to 40, can be found. First, CFEST and EHS stub column tests under centric compressive loading were performed and their design equations were discussed by Yang [2], Chan [3] and Zhao [4]. Secondly, Chan [5], Gardner [6] and Theofanous [7] carried out bending-shear tests on elliptical or oval steel/stainless beams through symmetrically three- or four-point loading tests. Thirdly, Ruiz [8] and Gardner [9] investigated the buckling behavior of the EHS long column. Next, aiming the application of gusset plate connection to the ends of the EHS, tensile test on three types of the EHS connections were also examined by Willbald [10] and Sauced [11]. Moreover, analytical study on the fire resistance of CFEST based upon non-liner FEM analysis was conducted by Episons [12]. Last, eccentric structural response of CFEST stub column under the combination of axial force and bending moment was investigated by Sheehan [13].

Under the above-described background, the present study aims to investigate, experimentally, the axial loading capacities of CFEST stub columns with large diameter-to-thickness ratio, which ranges from 69 to 160, and are to be applied to steel concrete bridge piers located in rivers. The three selected parameters are diameter-to-thickness ratio (2a/t and 2b/t), diameters ratio (a/b) and specimen׳s height (H), respectively. Discussion on confinement intensity effects induced by the elliptical/oval steel tubes is provided. Additionally, a method to predict the axial loading capacitiy of CFEST stub columns induced by the confinement strength of the in-filled concrete is also provided. Part of this study have been previously reported in Japan [14].

Section snippets

Test specimens

The details of the specimens are summarized in Table 1. Test specimens dimensions are combinations of different tube thicknesses (t), diameter ratios (a/b) and specimen heights (H). Thin steel plates (t=1.0, 1.6 and 2.3 mm) are bent into elliptical/oval shape, then both ends of the plate are welded to each other. The larger diameter 2a, common to all cross sections, is 160 mm and the smaller diameter 2b are 64, 80 or 107 mm, respectively; what provides diameter ratios a/b equal to 1.5, 2.0 or 2.5.

Failure modes

Fig. 4, Fig. 5, Fig. 6 show the typical failure modes of the specimens, in which a/b are 1.5, 2.0 and 2.5, respectively. As it can be seen from these figures, local buckling of the elliptical/oval tubes in the smaller diameter direction is associated with the shear failure of the in-filled concrete, which appeared from the top to the lower parts of the specimens. The observed failure mode is identical to the results obtained for ordinary CFT stub column test under centric compressive loading.

Estimations

Conclusions

Twenty-one specimens of concrete filled elliptical/oval steel tubular (CFEST) stub columns, with large diameter-to-thickness ratio ranging from 69 to 160, were tested under centric compressive loading. The following conclusions were derived from the results and discussion.

1.
The obtained failure modes were local buckling of elliptical/oval tubes associated with shear failure of in-filled concrete. This is the same failure mode as that observed in CFT stub column test under compression.
2.
Axial load

Acknowledgment

The author thank Mr. Shimizu, S., an Advanced Course Student in KCCT, for his sincere help to this experimental work. Moreover, the author would like to appreciate Ms. Ichinose LH, the group manager of Japan Industrial Testing Corporation, for correcting the draft in English of this manuscript.

References (14)

H. Yang et al.
Testing and analysis of concrete-filled elliptical hollow section
Eng Struct
(2008)
T.M. Chan et al.
Compressive resistance of hot-rolled elliptical hollow sections
Eng Struct
(2008)
X.L. Zhao et al.
Tests and design of concrete-filled elliptical hollow section stub columns
Thin-Walled Struct
(2009)
T.M. Chan et al.
Bending strength of hot-rolled elliptical hollow sections
J Construct Steel Res
(2008)
M. Theofanous et al.
Flexural behaviour of stainless steel oval hollow sections
Thin-Walled Struct
(2009)
A.M. Ruiz-Teran et al.
Elastic buckling of elliptical tubes
Thin-Walled Struct
(2008)
A. Espinos et al.
Fire behaviour of concrete filled elliptical steel column
Thin-Walled Struct
(2011)

There are more references available in the full text version of this article.

Cited by (89)

Numerical analysis and design of concrete-filled wire arc additively manufactured steel tube under axial compression
2024, Engineering Structures
Numerical investigation of the mechanical behaviour of concrete-filled wire arc additively manufactured (WAAM) steel tube under axial compression is presented in this paper. Typical structural performances of concrete-filled WAAM steel tube are extensively analyzed based on the experimental results firstly. FE models are established based on 3D models obtained by 3D laser scan technology, whilst the material anisotropy of WAAM steel tube is taken into account. The sensitivity study on the finite element (FE) model parameters is developed to assess their influence on the simulation results. The established FE models are veriﬁed against the test results demonstrating their effectiveness in predicting the structural behaviour of the concrete-filled WAAM steel tube. The composite action between the WAAM steel tube and inner concrete is analyzed through the validated FE models, indicating that it should be emphasized within the strain range from 0.003 to 0.01. The inﬂuences of the concrete and steel strengths are evaluated to investigate the confinement effect, showing that the concrete and steel strength exhibit a negative and positive impact on the confinement effect, respectively, and a positive correlation between the steel strength and biaxial stresses of the WAAM steel tube can be obtained. Finally, the design method of concrete-filled WAAM steel tube under axial compression, which considers the effect of the geometric undulations and material anisotropy of the WAAM steel tube, is proposed based on the theory of confining effect. The comparison results indicate that the proposed method can predict the axial compressive strengths of the concrete-filled WAAM steel tubes with reasonable accuracy.
Investigations on the seismic behaviour of concrete-filled thin-walled elliptical steel tubular column: Testing and novel FE modelling
2023, Thin-Walled Structures
This paper designs and tests a total of eight concrete-filled thin-walled elliptical steel tubular (CFEST) columns imposed with lateral cyclic load and axial force to acknowledge their seismic behaviour. The crucial seismic performance analyses on the failure modes, the seismic strength, the ductility index, the energy dissipation, the strength degeneration, and rigidity degeneration of the thin-walled CFEST columns are successively performed. Then a novel numerical analytical approach based on OpenSees software is developed initially by using a code programming process for the elliptical cross section. Particularly, the featured seismic properties of the CFEST column on the strength, rigidity and energy dissipation with respect to those of circular and square CFST columns are revealed. Development rules of CFEST columns’ seismic behaviour under the influence of various material and geometric parameters are investigated as well. Finally, calculation formulae for assessing the initial rigidity, peak force, peak displacement and descending rigidity of the CFEST column subjected to cyclic load are proposed. The findings indicate that the thin-walled CFEST column offers good seismic performance. Unlike the circular and square CFST columns, the outward local buckling failure of the steel tube is usually developed from the small to the large curvature regions. Under the same sectional area and steel ratio, the seismic resistance, initial rigidity, and energy dissipation of the CFEST column loaded along the major axis are much higher than those of the circular and square CFST columns, which should be fully used in engineering practice.
Post-fire performance of axially-loaded elliptical concrete-filled steel tubular stub columns
2023, Structures
This paper investigates the post-fire performance of elliptical concrete-filled steel tubular (CFST) columns by a series of post-fire axially-loaded stub column tests and numerical analysis. The test parameters included target temperature, high temperature duration time, section type and section size. A post-fire stress-strain relationship model of core concrete applicable to the elliptical CFST column was proposed according to the test data, and finite element analysis (FEA) model of the elliptical CFST column was established. Based on the FEA model, the temperature and deformation developments, failure mode, stress and load distributions of elliptical CFST columns were analyzed and discussed, and parametric analysis was further conducted to identify the key influencing factors on the post-fire ultimate bearing capacity and residual bearing capacity index of elliptical CFST columns. Finally, a simplified formula was proposed to calculate the post-fire residual bearing capacity index of elliptical CFST columns.
Compressive behaviour of elliptical FRP tube-confined concrete columns
2023, Composite Structures
Elliptical FRP tube-confined concrete columns (EFCCCs) are an extension of circular FRP tube-confined concrete columns recently proposed at The Hong Kong Polytechnic University. Like their circular counterparts, EFCCCs are corrosion-resistant and can be used in situations where a column is subjected to substantially different loads in the two orthogonal lateral directions. The elliptical section of EFCCCs leads to more effective confinement of the concrete and an easier filament-winding fabrication process for the FRP tube compared with their rectangular counterparts. Existing studies on FRP-confined concrete in elliptical columns have been few. This paper first presents a systematic experimental study on the axial compressive behaviour of EFCCCs, with a focus on the stress–strain behaviour of the confined concrete. The test variables included the concrete strength, the thickness and fibre orientations of the FRP tube, and the aspect ratio of the cross-section. The test results showed that the confinement effectiveness of FRP tubes decreases with the aspect ratio and the concrete strength but increases with the FRP tube thickness. The orientations of fibres in the FRP tube were found to have a significant effect on its confinement effectiveness and the failure mode of EFCCCs. On the basis of the test results, existing stress–strain models for FRP-confined concrete in elliptical columns are evaluated. Furthermore, a new stress–strain model for the concrete in EFCCCs is proposed, which includes a more rigorous treatment of the confinement stiffness of EFCCCs and can provide more accurate predictions for the whole stress–strain curve than the existing models.
Experimental, numerical and design investigations on the performance of axially-loaded ECFT stub columns with spherical-cap gaps
2022, Structures
Elliptical concrete-filled steel tubular (ECFT) columns have been increasingly used in engineering practice in recent years due to their aesthetic appeal together with structural advantages. The spherical-cap gaps were generally found in the actual CFT structures based on the latest survey. However, related literatures on the ECFT stub columns with spherical-cap gaps (ECFT-SG) under axial load are rarely reported. Thus, this paper aims to reveal the effects of gaps on the performance of axially-loaded ECFT stub columns. In total, ten axially-loaded ECFT-SG specimens were tested to explore the effects of gap ratio (χ_sg) and steel yield strength (f_y) on the failure modes, axial fore (N) – longitudinal shortening (Δ), strain responses, strength and ductility indexes, etc. Following this, a series of numerical models using a modified equivalent concrete stress-strain relationship were established to expand the parametric scope and further study the steel-concrete interaction stresses and the concrete longitudinal stress distribution. Finally, two strength prediction methods of ECFT-SG stub columns were presented. The results indicated that the initial concrete gaps would weaken the confinement effect provided by steel tube, thus decrease the initial stiffness, ultimate strength and ductility of the columns. With the χ_sg increasing, the overall bending and inward buckling phenomena would be observed because of the uneven damage of infill concrete. The two design methods proposed herein are expected to provide a reference to evaluate the safety of the existing CFT columns with initial gap imperfection.
Experimental investigation and theoretical analysis of axially-loaded concrete-filled elliptical tubes with circumferential gaps
2022, Thin-Walled Structures
This paper herein conducts an experimental investigation on the axial compression behaviour of the concrete-filled elliptical steel tubular (CFEST) short columns offering circumferential gaps (CFEST-CG) and explores the influence of gap ratio and steel strength on their failure modes, axial compression resistance, initial stiffness and ductility, etc. Moreover, a finite element (FE) model is built and validated by the test observations. A systemic parametric investigation is presented to explore the impact of geometric and material parameters on the axial compression properties of CFEST-CG short columns. The influencing mechanisms of the circumferential gap on the typical load–displacement curve, the stress response and the contact stress are figured out. Two simplified calculation approaches for estimating the axial compression strength of CFEST-CG short columns are proposed in accordance with the unified theory and the simple superposition principle. The research results indicate that the existence of circumferential gap defects may result in failure patterns, such as the brittle cracking of the concrete, the inward and outward bulges in steel tube, due to the weakened steel confining effect and concrete supporting action. And the significant decrease in the axial compressive strength, initial stiffness and ductility of the columns is obtained as well. The accuracy of the design methods is verified by experiments and FE parameter analysis, which would provide a reference for theoretical research and design of CFEST-CG short columns.

View all citing articles on Scopus

View full text

Experimental study on concrete filled elliptical/oval steel tubular stub columns under compression

Highlights

Abstract

Introduction

Section snippets

Test specimens

Failure modes

Estimations

Conclusions

Acknowledgment

Eng Struct

Eng Struct

Thin-Walled Struct

J Construct Steel Res

Thin-Walled Struct

Thin-Walled Struct

Thin-Walled Struct