Circular Hollow Section Columns Research Articles

Numerical investigation and design of aluminum alloy circular hollow section columns

This paper presents a numerical investigation of aluminum alloy circular hollow section non-welded and welded columns using finite element analysis. A non-linear finite element model was developed and verified against fixed-ended column tests. The column specimens were extruded from heat-treated aluminum alloys of 6063-T5 and 6061-T6, and the ends of the columns were transversely welded to aluminum end plates for the welded columns. The non-welded columns without welding of end plates were also investigated. The welded columns were modeled by dividing the column into different portions along the column length, so that the heat-affected zone softening at both ends of the welded columns was included in the simulation. The initial local geometric imperfections of the columns were measured in this study. Geometric and material non-linearities were incorporated in the finite element model. The verified finite element model was used for a parametric study of fixed-ended aluminum alloy circular hollow section columns. A comparison of the column strengths predicted by the finite element analysis and the design strengths calculated using the current American, Australian/New Zealand and European specifications for aluminum structures was presented. The column strengths were also compared with the design strengths predicted by the direct strength method, which was developed for cold-formed carbon steel members. Design rules were proposed for aluminum alloy circular hollow section columns with transverse welds at the ends of the columns. Reliability analysis was performed to evaluate the reliability of the design rules.

Eurocode structural fire design and its application for composite circular hollow section columns

The tabular structural fire design method for centrally loaded composite columns consisting of concrete filled steel circular hollow sections proposed in EN 1994-1-2:2005 (Eurocode 4: Design of Composite Steel and Concrete Structures - Structural Fire Design) is described here. A design procedure is then discussed, based on the determination of the temperature distribution in the cross sectional area and along the column length. A finite element based computer program is developed to implement the three-dimensional thermal analysis of different materials and geometries for given time versus temperature fire data. An example problem is shown, comparing the tabular method proposed in EN 1994-1-2:2005 and the method presented in this work.

Experimental behaviour of steel reduced beam section to concrete-filled circular hollow section column connections

In this paper, five specimens of connections of reduced beam section (RBS) steel beam to concrete-filled steel tubular (CFST) circular hollow section (CHS) column using an external ring were tested. The experiments considered the hysteretic behaviour under combined constant axial load and cyclic lateral load. For comparison, three specimens of a weak-column without an RBS configuration steel beam to CFST column connection were tested under the same conditions. The axial load level of the CFST column, width of connection stiffening ring and RBS configuration were considered as the experimental parameters of their seismic behaviour. It was found that the lateral load ( P ) versus lateral deformation ( Δ ) hysteresis curves exhibited no obvious strength deterioration and stiffness degradation. The energy dissipation of the RBS connections is significantly improved when compared with weak-column connections. The concrete filled CHS columns failed as a weak-column connection and their energy dissipation capacity was reduced. It can be concluded that the RBS connections exhibit good seismic performance.

Investigation of cold-formed stainless steel non-slender circular hollow section columns

Ehab Ellobody? Department of Structural Engineering, Faculty of Engineering, Tanta University, Tanta, Egypt Ben Young? Department of Civil Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong (Received September 13, 2006, August 13, 2007) Abstract. The investigation on the behaviour of cold-formed stainless steel non-slender circular hollow section columns is presented in this paper. The normal strength austenitic stainless steel type 304 and the high strength duplex materials (austenitic-ferritic approximately equivalent to EN 1.4462 and UNS S31803) were considered in this study. The finite element method has been used to carry out the investigation. The columns were compressed between fixed ends at different column lengths. The geometric and material nonlinearities have been included in the finite element analysis. The column strengths and failure modes were predicted. An extensive parametric study was carried out to study the effects of normal and high strength materials on cold-formed stainless steel non-slender circular hollow section columns. The column strengths predicted from the finite element analysis were compared with the design strengths calculated using the American Specification, Australian/New Zealand Standard and European Code for cold-formed stainless steel structures. The numerical results showed that the design rules specified in the American, Australian/New Zealand and European specifications are generally unconservative for the cold-formed stainless steel non-slender circular hollow section columns of normal and high strength materials, except for the short columns and some of the high strength stainless steel columns. Therefore, different values of the imperfection factor and limiting slenderness in the European Code design rules were proposed for cold-formed stainless steel non-slender circular hollow section columns.

Column design of cold-formed stainless steel slender circular hollow sections

This paper describes the design and behaviour of cold-formed stainless steel slender circular hollow section columns. The columns were compressed between fixed ends at different column lengths. The investigation focused on large diameter-to-plate thickness (D/t) ratio ranged from 100 to 200. An accurate finite element model has been developed. The initial local and overall geometric imperfections have been included in the finite element model. The material nonlinearity of the cold-formed stainless steel sections was incorporated in the model. The column strengths, load-shortening curves as well as failure modes were predicted using the finite element model. The nonlinear finite element model was verified against test results. An extensive parametric study was carried out to study the effects of cross-section geometries on the strength and behaviour of stainless steel slender circular hollow section columns with large D/t ratio. The column strengths predicted from the parametric study were compared with the design strengths calculated using the American Specification, Australian/New Zealand Standard and European Code for cold-formed stainless steel structures. It is shown that the design strengths obtained using the Australian/New Zealand and European specifications are generally unconservative for the cold-formed stainless steel slender circular hollow section columns, while the American Specification is generally quite conservative. Therefore, design equation was proposed in this study.

Experimental investigation of aluminum alloy circular hollow section columns

This paper presents an experimental investigation of aluminum alloy circular hollow sections subjected to pure axial compression between fixed ends. The specimens were fabricated using 6063-T5 and 6061-T6 heat-treated aluminum alloy. The test program included 29 column tests which were separated into 4 test series of different type of aluminum alloy and cross-section geometry. Each test series contained at least 5 columns with both ends transversely welded to aluminum end plates using the Tungsten Inert Gas welding method, and 2 columns without welding of end plates. Hence, the effects of welding on aluminum alloy columns could be investigated. The specimen length ranged from 300 to 3000 mm in order to obtain a column curve for each test series. The observed failure modes for the column tests include yielding, overall buckling, and material yielding in the heat-affected zone. The test strengths were compared with the design strengths predicted by the American, Australian/New Zealand and European specifications for aluminum structures. The purpose of this paper is to present the test results of aluminum alloy circular hollow section columns with and without transverse welds, and to check the accuracy of the design rules in the current specifications.

Cyclic performance of concrete-filled steel CHS columns under flexural loading

Concrete-filled steel CHS (circular hollow section) columns are currently being increasingly used in the construction of buildings. Limited information is available on the models for the moment ( M ) versus curvature ( ϕ ) response, and the lateral load ( P ) versus lateral displacement ( Δ ) relationship of these columns subjected to axial load and cyclically increasing flexural loading. Eight concrete-filled steel CHS specimens were tested under constant axial load and cyclically increasing flexural loading. The parameters in the study included the concrete strength ( f cu ) and the axial load level ( n ) . A mechanics model is developed in this paper for concrete-filled steel CHS columns subjected to constant axial load and cyclically increasing flexural loading. The predicted cyclic responses for the composite columns are in good agreement with test results. Based on the theoretical model, parametric analysis was performed on the behaviours of the moment ( M ) versus curvature ( ϕ ) response, and the lateral load ( P ) versus lateral displacement ( Δ ) relationship, as well as the ductility coefficient ( μ ) for the composite columns. Finally, simplified models for the moment ( M ) versus curvature ( ϕ ) response, and the lateral load ( P ) versus lateral displacement ( Δ ) relationship are suggested. A formula for the calculation of the ductility coefficient ( μ ) of the composite columns under constant axial load and cyclically increasing flexural loading is developed.

Behaviours and Strengths of Concentrically Loaded Short Concrete-Filled Steel HS Columns with Different Cross-Section Geometries

This paper presents the stress distribution, confinement distribution and complete average longitudinal stress-strain curves for concentrically loaded short concrete-filled steel circular, octagonal, square and rectangular hollow section (HS) columns using 3-D finite element (FE) analyses. The curves predicted by FE analyses are in good agreement with those obtained from previous experimental work. The compressive design strengths and the compressive moduli of concrete-filled steel HS columns are also obtained. A unified method is proposed for the design of concentrically loaded short concrete-filled steel HS columns with different cross-section geometries.

Compression Tests of Stainless Steel Tubular Members

A series of tests consisting of three cross-section geometries was performed on cold-formed stainless steel circular hollow section (CHS) columns compressed between fixed ends. The specimens were cold rolled from stainless steel sheets. The tests were performed over a range of column lengths, which involved local buckling and overall flexural buckling. Measurements of overall geometric imperfections and material properties were conducted. The test strengths are compared with the design strengths predicted using the American, Australian/New Zealand and European specifications for cold-formed stainless steel structures as well as the column strengths obtained from the design rules proposed by Rasmussen and Hancock in 1993 and Rasmussen and Rondal in 1997. Generally, the specifications unconservatively predict the strengths of the tested CHS columns, while Rasmussen and Hancock; and Rasmussen and Rondal conservatively predict the column strengths. The reliability of these design rules is evaluated using reli...

Recent research on stainless steel tubular structures

The paper summarises research undertaken at the University of Sydney during the 1990s on stainless steel tubular members and connections. The tubes were cold-formed from annealed AISI 304L austenitic stainless steel coil strip. Tests were performed on square, rectangular and circular hollow section columns and beams, as well as welded X- and K-joints in square and circular hollow sections. The paper summarises the design rules proposed on the basis of the tests and describes how these rules are being implemented in the first Australian standard for stainless steel structures currently in preparation.

Some considerations in the design of unprotected concrete-filled steel tubular columns under fire conditions

This paper is concerned with the fire resistant design of centrally loaded unprotected concrete-filled steel tubular columns using Eurocode 4 Part 1.2. It addresses three issues: the column buckling curve to be used for elevated temperature design, the implementation of the calculation method in Eurocode 4 Part 1.2 and the equivalent time of fire exposure. The predicted column fire resistance using the Eurocode 4 Part 1.2 calculation method is compared with the results of tests on 36 concrete-filled circular hollow section columns and seven square hollow section columns conducted at the National Fire Laboratory of Canada. This comparative study indicates that the choice of column buckling curve for elevated temperature design depends on the adopted concrete strength and stiffness-temperature models. If the models in the main text of Eurocode 4 Part 1.2 are used, column buckling curve ‘a’ seems to give more accurate results. For the standard fire resistant design, this paper proposes a simple method to implement the general calculation method in Eurocode 4 Part 1.2. This proposed method is easy to use and was demonstrated to be quite accurate. Using the parametric time-temperature relationships in Eurocode 1 Part 2.2 to represent the behaviour of realistic fires, this paper studies the equivalent time approach, based on the column resistance. Results from this study show that the equivalent time equation in Eurocode 1 Part 2.2 needs modifying to allow for the inter-dependence between fire load and ventilation factor and this equation is also unsafe. This paper further suggests introducing a multiplication factor in the equivalent time equation to cater for different types of construction element.

Calculation of the fire resistance of steel hollow structural section columns filled with plain concrete

Experimental studies were conducted to determine the fire resistance of circular and square hollow structural section columns filled with plain concrete. Mathematical models were developed and used to investigate the influence of important parameters that determine the fire resistance of these columns. The experimental and parametric studies provide information for the development of formulas for the calculation of the fire resistance of circular and square concentrically loaded columns filled with plain carbonate or siliceous aggregate concrete. Such formulas are suitable for incorporation into building codes. Key words: calculation, fire resistance, columns, concrete-filled, steel, hollow structural sections.