Concrete-filled Elliptical Hollow Section Research Articles

The behaviors of concrete-filled elliptical hollow section steel stub columns under different interface states

The behaviors of concrete-filled elliptical hollow section steel stub columns under different interface states

Numerical analysis and design of slender concrete-filled elliptical hollow section columns and beam-columns

A numerical model simulating the behaviour of elliptical concrete-filled columns under either concentric or eccentric compressive load has been developed in ABAQUS. The numerical results have been compared against a range of experimental results for ultimate load, load–deflection behaviour and failure modes, with good agreement observed. An extensive parametric study has been undertaken whereby the slenderness, load eccentricity, cross-sectional geometry and reinforcement ratio of the concrete-filled columns were varied, creating a data set upon which to formulate design guidance since currently there are no specific provisions in the European Standard EN 1994-1-1 [1] for the design of concrete-filled steel elliptical section columns or beam-columns. It is shown that the current provisions of EN 1994-1-1 [1] for the design of concrete-filled steel columns of circular or rectangular cross-section are also appropriate for the design of members of elliptical cross-section, employing either buckling curve b or c, depending on the level of steel reinforcement. Finally, an assessment is made of the reliability of the design proposals for concrete-filled elliptical hollow section columns and beam-columns.

Experimental study of slender concrete-filled elliptical hollow section beam-columns

Experiments on concrete-filled elliptical hollow section beam-columns have been conducted to examine their fundamental structural behaviour. A total of 27 specimens were tested — 3 stub columns and 24 longer members of varying slenderness. Seven of the tested specimens also contained steel reinforcement. The specimens were loaded in compression, either concentrically or with different major or minor axis eccentricities. Measurements of the applied load, the strains at mid-height, the axial displacement and the lateral deflection at mid-height were recorded. Plots of load against the lateral deflection at mid-height and load against axial displacement are presented for the specimens, along with values of strength index and ductility index. Comparisons have been made between the test results and the provisions of the European Standard EN 1994-1-1:2004 for determining the ultimate load of concrete-filled circular and rectangular hollow section columns. It was found that the predicted resistances are safe for use in the design of concrete-filled elliptical hollow section columns either with or without reinforcement, and loaded either concentrically or eccentrically.

Fire behaviour of concrete filled elliptical steel columns

In this work, a non-linear three-dimensional finite element model is presented in order to study the behaviour of axially loaded concrete filled elliptical hollow section (CFEHS) columns exposed to fire. This study builds on previous work carried out by the authors on concrete filled circular hollow section (CFCHS) columns both at room temperature and in fire. The numerical model is first validated at room temperature against a series of experiments on CFEHS stub columns available in the literature and subsequently extended to study the performance of slender columns at elevated temperatures. The aim of this work is to understand and represent the behaviour of axially loaded CFEHS columns in fire situations and to compare their effectiveness with that of the circular concrete filled tubular (CFT) columns. Parametric studies to explore the influence of variation in global member slenderness, load level, cross-section slenderness and section size are presented. Finally, guidance on the fire design of CFEHS columns is proposed: it is recommended to follow the guidelines of Clause 4.3.5.1 in EN 1994-1-2, but employing the flexural stiffness reduction coefficients established in the French National Annex with an equivalent EHS diameter equal to P/π, where P is the perimeter of the ellipse.

Behaviour of Axially Loaded Concrete Filled Stainless Steel Elliptical Stub Columns

This paper presents the details of an experimental investigation on the behaviour of axially loaded concrete-filled stainless steel elliptical hollow sections. The experimental investigation was conducted using normal and high strength concrete of 30 and 100 MPa. The current study is based on stub column tests and is therefore limited to cross-section capacity. Based on the equations proposed by the authors on concrete-filled stainless steel circular columns, a new set of equations for the stainless steel concrete-filled elliptical hollow sections were proposed. From the limited data currently available, the equation provides an accurate and consistent prediction of the axial capacity of the composite concrete-filled stainless steel elliptical hollow sections.

Tests and design of concrete-filled elliptical hollow section stub columns

Similar to concrete-filled tubular columns, void-filling of elliptical hollow sections (EHS) will produce increased strength, stiffness, energy absorption and fire resistance. Stub column tests on unfilled EHS were performed first. Discussions are made on the equivalent diameters in the literature for deriving the yield slenderness limit. An equivalent rectangular hollow sections (RHS) is proposed to derive such a limit for EHS sections in axial compression. An experimental investigation has also been carried out on the behaviour of concrete-filled EHS stub columns. Both normal concrete and self consolidating concrete (SCC) were used in the testing program. Different loading methods were investigated; e.g., loading through steel alone, loading through concrete alone and loading through the whole cross-section. This paper is based on experimental data on carbon steel EHS with an aspect ratio of 2, which is also the only product type currently produced. The load carrying capacity is compared with that predicted using EC4 and CAN/CSA-S16. Proposed design formulae are given.

Testing and analysis of concrete-filled elliptical hollow sections

Concrete-filled steel tubes are gaining increasing prominence in a variety of engineering structures, with the principal cross-section shapes being square, rectangular and circular hollow sections. A recent addition to this range has been that of elliptical hollow sections. The structural response of empty elliptical tubes has been examined in previous studies. In this paper, the cross-sectional axial behaviour of concrete-filled elliptical hollow sections is investigated. An experimental programme comprising a total of 21 test specimens, with three nominal tube thicknesses (4 mm, 5 mm and 6.3 mm) and three concrete grades (C30, C60 and C100) has been performed. The effects of steel tube thickness, concrete strength and constraining factor on elastic stiffness, ductility and ultimate strength were studied. To simulate the effects of concrete shrinkage, the inner surfaces of 6 of the 21 test specimens were coated with grease prior to casting. To investigate confinement effects, a further 6 of the 21 test specimens were loaded through the concrete core only. The results of the tests presented herein were combined with those from previous studies, and compared with existing design provisions for square, rectangular and circular concrete-filled tubes. The design expressions from current European, North American, Japanese, British and Chinese Standards were assessed. On the basis of the comparisons, design recommendations for concrete-filled elliptical hollow sections have been made.