Steel Tubular Sections Research Articles

Fire design of steel-reinforced CFST stub columns with high-strength materials

Innovative composite sections are gaining popularity as they reduce the environmental impact of construction and take advantage of the collaboration of concrete and steel properties at room temperature and in fire. By introducing high-performance materials, these synergies are boosted. One typology is the steel-reinforced concrete-filled steel tubular (SR-CFST) section, in which a steel profile is embedded inside a CFST section. Despite their impressive load-bearing capacity and fire resistance, the available investigations on their thermo-mechanical capabilities are scarce. The present paper develops a numerical model to analyse the thermo-mechanical behaviour of SR-CFST stub columns subjected to fire. The model is validated against previous experiments conducted by the authors by comparing the temperature distribution and the mechanical behaviour with the experimental measurements. Afterwards, an extensive parametric study (1440 cases) is conducted to analyse the influence of several geometrical parameters – cross-sectional shape, outer tube dimensions and thickness, inner steel profile dimensions, section factor – and the use of high-strength materials for the concrete and the inner steel profile. Afterwards, a simplified temperature distribution proposal formerly designed by the authors for SR-CFST sections was tentatively tested. Based on this previous simplified temperature field and in line with the current provisions of EN1994-1-2, a new proposal is developed to evaluate the cross-sectional plastic resistance of SR-CFST stub columns under a fire scenario. This method unifies the initially developed thermal method and provides practical guidance for designers to evaluate the thermo-mechanical behaviour of SR-CFST columns, filling an existing gap in the European design code.

A comprehensive methodology for residual capacity evaluation of damaged steel tubular columns

Steel tubular sections are extensively used in modern-day construction due to their superior structural efficiency and aesthetic appearance. The thin-walled tubular sections are often subjected to accidental loading due to heavy object impact, collision, or improper handling during transportation. Due to induced geometric defects by unanticipated loads, the load-carrying capacity of the section decreases. This study proposes a methodology to estimate the residual capacity of damaged circular and square tubular specimens in axial compression. Initially, the specimen's surface coordinates were obtained in the form of a dense point cloud using a 3D digital image correlation (DIC) setup. Using a linear interpolation function based on Delaunay triangulation, the dense point cloud was regularized into a set of sparsely spaced nodes that would yield computationally efficient finite element (FE) analysis. The interpolation introduced errors at the locations of sharp curvature on the surface. A systematic smoothing (filtering) approach was proposed to minimize the effect of the interpolation error. The proposed methodology was validated against compression tests on five damaged and three as-built specimens, which consisted of circular and square tubular sections. The average residual strength estimated was found to be 93% of the experimental observations.

Web crippling tests of cold-formed stainless steel tubular sections at elevated temperatures

This paper presents an experimental investigation on web crippling behaviour of cold-formed stainless steel square and rectangular hollow sections (SHS and RHS) at elevated temperatures. A total of 21 web crippling tests were conducted under the Interior Two-Flange (ITF) loading condition as codified in ASCE/SEI 8–22 Specification at various temperatures up to 800 °C. Tensile flat and corner coupon tests were conducted to obtain the material properties of the cold-formed stainless steel SHS and RHS at various temperatures corresponding to those pre-set in the web crippling tests. Details of the test specimens, setups and procedures are comprehensively documented in this paper. Furthermore, the specimen temperatures together with the test results, including failure modes, web crippling strengths and load-deformation curves are fully reported. The obtained test results were used to evaluate the suitability of codified web crippling design provision as per ASCE/SEI 8–22, where reduced material properties were used in calculating the web crippling strengths at elevated temperatures. In addition, the test results were also compared with the predictions obtained from existing design rules in literatures for cold-formed stainless steel SHS and RHS at elevated temperatures. Moreover, reliability analyses were conducted to assess the reliability levels of these design provisions. It is demonstrated that the available web crippling design provisions can provide generally conservative and reliable strength predictions, and therefore are deemed suitable for predicting the web crippling strengths of cold-formed stainless steel SHS and RHS at elevated temperatures.

Static behavior of multi-planar CFST chord-CHS brace TT joints

The static performance of the multi-planar concrete-filled steel tubular (CFST) chord-circular hollow section (CHS) brace TT (CFST-TT) joint is investigated using theoretical and finite element analysis (FEA). The joint ultimate bearing capacity is the minimum strength of each member to ensure that the joint will not fail under any loads. Accordingly, the strength calculation formulas for joints are proposed based on the failure mechanism. FEA models verified by experiments were established to obtain the joint bearing capacity and failure modes, and further analysis was done to find the effects of geometrical parameters, material strength, and the axial compression ratio. The results show that the joint bearing capacity increased with the increase of brace-to-chord diameter ratio (β) and steel yield strength of the chord (fy) but decreased with the increase of the chord diameter-to-thickness ratio (γ). However, the concrete compressive strength (fcu), the brace-to-chord thickness ratio (τ), the angle between two braces (Ф), and the axial compression ratio (n) almost have no effect on the joint bearing capacity. The proposed ultimate bearing capacity formula is validated using FEA. The optimized formula is proposed to simplify the theoretical calculation formula and make the results more consistent with the FEA results.

Strengthening Stainless Steel Tubular Beams using Fibre-reinforced Concrete incorporating Sugarcane Bagasse Ash

Stainless steel tubular beam sections have been increasingly utilised for structural applications due to the enhanced properties of stainless steel over conventional mild steel. However, thin-walled stainless steel sections are not effectively used for several practical applications due to the higher costs and its response to easily undergo local buckling under flexural loading. Consequently, to overcome these effects, concrete infilling is a generally preferred strengthening mechanism that enhances the overall capacity and makes the sections economic. Earlier research studies on the flexural behaviour of various concrete-infilled stainless steel composite beam specimens are highly limited. Therefore, this study mainly focuses on the flexural behaviour of bare stainless steel tubular beams, sugarcane bagasse ash blended concrete-infilled stainless steel composite beam, and fibre-reinforced sugarcane bagasse ash blended concrete-infilled stainless steel composite beam. The study uses sugarcane bagasse ash as a pozzolan in the infill concrete to produce durable and sustainable concrete. In the same manner, crimped steel fibres are incorporated to enhance the ductility of the beam specimen. The parameters such as ultimate strength, maximum flexural deformation, initial stiffness, failure modes, ductility, and moment-rotation profiles were comprehensively investigated for all the beam specimens. Furthermore, numerical modelling was performed for the fibre-reinforced sugarcane bagasse ash blended concrete-infilled stainless steel composite beam specimen and was validated with the experimental results. It was witnessed that adding infill concrete to the stainless steel tube enhanced the beam specimens' load-carrying capacity, stiffness and ductility.

Load introduction and transfer mechanism of K-type CFST circular section connections

This paper investigates the mechanism of load introduction and transfers for K-type concrete-filled steel tubular (CFST) circular section connections experimentally and numerically. Six K-type CFST connections were tested. Three-dimensional finite element (FE) models were then developed and validated against the test results, where the degradation and failure of the direct bond interaction were considered explicitly. The longitudinal strain distribution along the circumferential direction of chord-wall demonstrated that the non-uniform force transfer in the chord was caused by the one side load introduction through braces. The effects of the chord length, cross-sectional slenderness and interfacial interactions on the force transfer of tube-concrete interface were evaluated: 1) the chord length above the connecting region has a positive influence on the force transfer; 2) for the K-type CFST connections in this study, the material strength of concrete in the chord with non-compact and slender sections could not be fully utilized due to the insufficient force transfer; 3) the direct shear interaction dominated the force-transferring process from chord-wall to concrete for the compact section chord with reinforcing plates. Furthermore, the test and FE result confirmed that the load introduction length of the CFST chord with braces included the chord above the connecting region and the full connecting region. In addition, the equation of effective load introduction length for the CFST chord of the K-type connections was proposed.

Influence of anchored orbicular rings on the performance of sandwich concrete‐filled double‐skin steel tube columns

AbstractSince 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.

Experimental residual capacity of steel-reinforced concrete-filled steel tubular stub columns after fire exposure

Technological advances in the development of steel–concrete composite structures have led to the introduction of novel types of sections in the sought of higher load-bearing capacities. Particularly for composite columns, the axial capacity of concrete-filled steel tubular (CFST) sections may be enhanced by the introduction of an open steel profile embedded within the concrete infill, forming the so-called steel-reinforced concrete-filled steel tubular (SR-CFST) columns. An important aspect that should be revised, in order to safely use these sections in design, is their performance after a fire. In this experimental program, six SR-CFST stub columns are tested in the post-fire situation. Two series of columns comprising three circular and three square sections with the same steel usage are tested for comparison purposes. The size of the inner steel profile is varied in order to investigate its effect over the post-fire capacity of the columns. The specimens were initially exposed to elevated temperatures inside an electric furnace, and then cooled to ambient temperature; afterwards compressive axial load was applied gradually until failure, to ascertain their residual capacity. The experimental results show the high ductility of the SR-CFST stub columns after heating, with the circular specimens reaching higher post-fire peak loads than their square counterparts. This load increases with the size of the embedded steel profile. The post-fire capacities of the columns are evaluated through the Residual Strength Index, showing similar values for both circular and square SR-CFST columns. Finally, a design equation is proposed to facilitate the evaluation of the post-fire compression resistance of SR-CFST columns, as an extension of the existing room temperature design equation in Eurocode 4 Part 1–2 for CFST columns, accounting for the degradation of the steel and concrete after fire exposure through the corresponding residual factors.

Study of Mechanical Characteristics of Steel Tubular Sections Filled with High-Volume Rubberized Concrete

Study of Mechanical Characteristics of Steel Tubular Sections Filled with High-Volume Rubberized Concrete

Design of multi-cell T-shaped concrete-filled steel tubular columns under compression and bending

To date, a number of studies have been done on the calculation methods for predicting bearing capacities of multi-cell special-shaped concrete-filled steel tubular (MS-CFST) columns under axial, pure bending, and eccentric load. However, most of the existing methods only apply to a specific combination form of cross-section and have not been established in a unified formulation. In this study, finite element (FE) models were established to predict the performances of the four common combination forms of multi-cell T-shaped concrete-filled steel tubular (MT-CFST) sections subjected to axial, eccentric, and pure bending loads, and verified with the available test data. The parametric analyses were conducted to investigate the effects of steel thickness t, concrete strength fck, steel yield strength fy, aspect ratio of the web c/b, and slenderness ratio λ on the flexural and eccentric compressive performance based on the FE models. The study results demonstrated that the four common combination forms of MT-CFST sections showed the same changing trends of flexural capacity with different parameters, and the flexural capacity rose almost linearly with the increase of the parameters. The parameters (t, fy, fck, c/b, and λ) had a definite effect on the N/Nu-M/Mu correlation curve, especially c/b and λ. Furthermore, by analyzing the stress distribution of mid-span cross-section at ultimate state, the simplified calculation model for asymmetric flexural capacity applicable to different combination forms of MT-CFST section was put forward. The reduction factor of 0.9 for positive flexural capacity (WC) and the restricted width-to-thickness ratio 60235/fy are recommended. Based on the study of the constraint stress of steel tube to core concrete and the concrete constraint region distribution for the columns subjected to compression, the calculation method for predicting the axial bearing capacity applicable to different combination forms of MT-CFST section was proposed. According to the parametric analysis and shape of N/Nu-M/Mu correlation curve, the simplified method for N/Nu-M/Mu correlation curves applicable to different combination forms of MT-CFST sections was developed, which simultaneously took the influence of slenderness ratio into consideration. Besides, the calculation methods for MT-CFST members proposed in this paper have been verified with available test results and FE ones.

Component model and design method for tensile behavior of slip-critical blind bolts anchored in concrete-filled steel tubular sections

This paper derives a component model to capture the tensile behavior of concrete-anchored slip-critical blind bolt (CASCBB) anchored in concrete-filled steel tubular sections (CFSTS). CASCBB is developed based on a rare blind bolting system which can achieve the same pre-tension as the conventional high strength bolts, i.e. SCBB, good for enhancing the stiffness and seismic performance of joints. Based on the previous experiments and simulation method, a series of parametric studies are performed on the tensile behavior of CASCBB connections. The effect from the parameters is studied in details, revealing the load-carrying mechanism of the connection. The component model mainly including tube face, anchored bolt shank and two concrete struts is derived. Each element has contribution to initial stiffness and yield load. In the second stage, one of the struts fails and the other one is damaged. The ultimate strength can be simplified as the sum of resistance from tube face and diagonal concrete strut. The theoretical model has a good match with finite element analysis (FEA). A simple and practical design method is proposed for determining the configurations and strength of CASCBBs in tubular sections under tensile load. The process of stiffness estimation is also given for such connection.

Tests of concrete-filled high strength steel RHS and SHS beams

This paper presents an experimental investigation of concrete-filled high strength steel tubular (CFHSST) beams. A total of 35 four-point bending tests were conducted, covering high-strength steel square and rectangular hollow sections with nominal 0.2% proof stresses of 700 MPa and 900 MPa. Each high strength steel tubular section was filled with concrete materials of strengths equal to 40, 70 and 110 MPa, respectively. Hollow steel tubes were also tested for comparison purpose. Moment capacity of the test specimens was measured, and ductility of the test specimens was calculated, in order to evaluate the structural benefit associated with the composite action between the two materials. It was shown that both moment capacities and ductility of the CFHSST beams were significantly increased compared to the corresponding hollow sections without concrete infill. It should be noted that the very high strength steel material of 900 MPa is not covered in any design provisions. The current design equations were derived based on normal steel and concrete grades. The suitability of the current design rules, including American Specification (AISC) and European Code (EC4), was assessed for concrete-filled high strength steel tubular sections subjected to bending.

コンクリート充填角形鋼管断面の単純累加強度時の応力状態

The purpose of this study is to clarify the stress distribution of the cross-section at the simple superposed strength of concrete filled square steel tubular section. The moment-axial force relationships correspond to the simple superposed strength are calculated based on the Navier’s hypothesis. Analytical parameters are strength of concrete and steel tube and the width-to-thickness ratio. The stress or strain at the outermost edges of concrete and steel tube cross section with the stress or strain at allowable stress of the respective materials are compared and the relationship between the stress or strain of the cross-section at the simple superposed strength and the analytical variables are discussed.

Drift-flux correlation based on coaxial line phase sensor in a horizontal slug flow

In two-phase flow, void fraction plays an important role in the pressure gradient calculation and the flow pattern analysis, while the distribution parameter C0 and drift velocity ugm are crucial parameters in the establishment of drift flux void fraction correlation. Since the distribution parameter and drift velocity in the constitutive equation cannot reflect the influence of gas–liquid velocity and pressure in most existing correlations, theoretical and experimental studies are carried out to solve these problems in this study. The electromagnetic wave coaxial line phase sensor is designed for void fraction measurement, and the horizontal slug flow experiments (63 data points) have been conducted in a stainless steel tubular test section with an inside diameter of 50.0 mm. A comparison of the performance of thirteen existing drift-flux predictive correlations based on current and literature data (with different pressures (0.1–0.6 MPa) and pipe diameters (19–101.6 mm)) is made. Based on comparative analysis, the L-M parameter X, the liquid mass quality ratio to gas mass quality (1-x)/x and superficial velocity um are chosen to optimize the structure of existing models. A new drift flux correlation that could handle different phase velocities and system pressure is proposed. Experimental results indicate that the mean absolute percentage error (MAPE) of the distribution parameter and drift velocity correlations are 5.88 % and 27.37 %. The MAPE of the drift flux void fraction is 6.98 % (current data) and 11.07 % (literature data), respectively.

Experimental study on additive manufactured 304L stainless steel tubular sections: Material properties and cross-sectional behavior

This paper presents an experimental investigation on the material properties and cross-sectional behavior of 304L stainless steel tubular sections additively manufactured using selective laser melting (SLM). A total of 76 tensile coupons, 76 hardness test specimens, and 25 stub columns were fabricated from 304L stainless steel powders by the SLM technique. Tension coupon tests and hardness tests were conducted to determine the mechanical properties. Residual stresses and local geometric imperfections of the stub columns were measured. The effects of coupon specimen orientations, thicknesses, and annealing conditions on the measured material properties were explored. In addition, the failure modes, ultimate load-carrying capacities and structural responses of the stub columns with four different cross-sections under axial compression were obtained and analyzed to evaluate the cross-sectional behavior. The test results of ultimate strengths were compared with the predictions calculated from the current design methods. The test results showed that the tensile strength of the coupon perpendicular to the building direction was higher than that of the coupon parallel to the building direction. Moreover, the tensile strength of the coupon increased with the increase of the coupon thickness. Considering the cross-sectional behavior, the square hollow section (SHS) and circular hollow section (CHS) had greater cross-sectional axial capacities than the rectangular hollow section (RHS) and elliptical hollow section (EHS), respectively. The introduction of a single stiffener in SHS and CHS reduced the load-carrying capacities to a certain extent.

Numerical Investigation on the Thermal Behaviour of Steel‐reinforced CFST Columns in Fire

AbstractIn previous research, the authors highlighted the limited fire resistance of slender concrete‐filled steel tubular (CFST) columns. A possible solution for enhancing the fire resistance of such columns consists of embedding an open steel profile within the concrete infill of the CFST section, generating the so‐called steel‐reinforced concrete‐filled steel tubular (SR‐CFST) section, where the inner steel profile results thermally protected by the surrounding concrete, thus delaying its degradation at elevated temperatures. This strategy may result beneficial in the fire situation as compared to other sectional configurations where the steel parts are directly exposed to the heat source.In this paper, a two‐dimensional finite element model will be developed for studying the thermal behaviour of SR‐CFST columns and validated by comparing the temperature distribution results with experimental tests available in the literature. The numerical model will be subsequently used to carry out parametric studies, in order to analyse the influence of the different parameters, such as the cross‐section shape, outer tube thickness or the inner steel profile sectional dimensions over the thermal response of these composite sections when subjected to fire.Finally, a simplified temperature distribution proposal will be developed, which may help practitioners for a fast evaluation of the cross‐sectional temperature field of SR‐CFST columns at a given fire resistance period by assigning an equivalent temperature to each component of the composite section (hollow steel tube, concrete encasement and inner steel profile). This simplified temperature proposal may result helpful when evaluating the sectional capacity of SR‐CFST columns in fire, by using a single strength and stiffness value for each component of the composite cross‐section corresponding to its temperature.

On the uniform torsional rigidity of square concrete-filled steel tubular (CFST) sections

There are a number of scenarios in which structural members experience torsion, including under the direct application of torsional loading, when transverse loading is applied at an eccentricity to the shear centre and as a second order effect arising from lateral torsional instability. To date, the torsional rigidity of concrete-filled steel tubular (CFST) sections has yet to be fully explored; hence a study into the uniform torsional rigidity of square CFST sections is presented herein. First, the strain energy of square CFST sections is formulated, in which the longitudinal warping displacement is assumed to have an undetermined constant. The undetermined constant is then deduced by means of the principle of minimum strain energy, and thus an analytical expression for the uniform torsional rigidity of square CFST sections is obtained. The accuracy of the derived formula is verified against existing theoretical solutions for simplified scenarios, test data and the results of numerical simulations. Finally, the influence of the key parameters in the derived formula for the torsional rigidity of square CFST sections are analysed, and a simplified design formula is presented.

Investigation of cyclic behavior of full-scale tree-like hollow structural section columns with infilled concrete

The cyclic behavior of tree-like hollow structural section (HSS) columns with infilled concrete was experimentally and numerically investigated. A full-scale column, with the height of 3.7 m and the treetop plan dimension of 4 m × 3 m, was designed and manufactured according to a practical engineering prototype. The column was composed of a petal-shaped trunk using a concrete-filled steel tubular (CFST) section, four primary branches using a circular CFST section, and twelve secondary branches using a circular HSS. The column with a capacity protected reinforced concrete foundation was tested under combined constant axial compression and cyclic lateral loading through a specifically designed setup. The cracking and spalling of the reinforced concrete foundation were observed initially, followed by yielding of the bottom end of the primary branches when the story drift ratio reached 1.00%. The specimen failed by fracture of the full penetration groove welded splices in the petal-shaped trunk embedded in the foundation when the story drift ratio reached 3.00%. A detailed finite element analysis model for the tree-like column was then established and verified. Parametric studies were conducted to investigate the influence of the axial load level (0.016–0.3), filling range of concrete (including no filling, partial filling, and overall filling), steel yield strength (235–460 MPa), and the height to width ratio of the petal-shaped trunk (0.75–3.14). The results showed that the higher the filling height of concrete was, the greater the lateral load-carrying capacity and stiffness of the specimen were, but the filling height after reaching the secondary branches hardly affected the mechanical properties of the specimen. With the increase of the axial load level, the load-carrying capacity and deformation capacity decreased. Both the filling range and the height to width ratio of the petal-shaped trunk could change the failure mode of the tree-like column. Finally, some design considerations were proposed.

Welding procedure qualification record (WPQR) for welds fabricated at proximity

Maintaining the minimum allowable distance between proximity welds has always been considered a subject of debate among design engineers, welding engineers/inspectors and fabricators/engineering contractors. The scattered nature of guidelines available in welding codes and standards for maintaining the minimum allowable distance poses a significant challenge in the welding procedure and inspection criteria development process. This is especially critical for complex welded joints on submerged sections of offshore structures, in compact layouts/branched connections of topside piping components, and on topside structural joints (depending on the complexity). This manuscript presents the findings of an experimental study that was performed by fabricating two girth welds at proximity on an S355 steel tubular section with diameter of 219.1 mm and thickness of 8.18 mm. Proximity girth welds were fabricated on S355 tubular sections at three different distances between their weld toes, 5, 10, and 15 mm, respectively, using two different welding procedures. Welding procedure qualification record (WPQR) was performed, and all prescribed mechanical tests were recorded as per NORSOK M-101, a structural steel fabrication code. Although all results from the mechanical test met the minimum specified values as defined in the NORSOK code, the research findings revealed a noticeable difference in Charpy and hardness values for proximity region between adjacent welds. Considerable changes in final microstructure morphology were observed between proximity welds due to varying thermal cycles. These observations can form the basis for the future welding procedure qualification of critical welded joints, especially for proximity welds on critical welded joints of offshore structures and welds fabricated during replacement/repair procedures in compact piping layouts.

Mechanical properties of low-alloyed YSt-355-FR (0.126%Mo) cold-formed steel tube at elevated temperatures

With the advancement in the steel-making process, micro-alloyed steels with small amounts of Nb and Mo, etc., have been developed, which can retain superior strength at higher temperatures. Towards this end, this study investigates a newly developed low-alloyed YSt-355-FR cold-formed steel having Mo content less than 0.15% through the evaluation of the mechanical properties of its hollow steel sections. The standard tension tests on 84 tensile coupons taken from every region (non-welded, welded, and corner) of hollow steel cross-section at steady-state were conducted at temperatures between 20 °C and 800 °C with 120 min holding time. The stress-strain curves were plotted at different temperature levels, and results were discussed in terms of reduction factors of key strength and stiffness properties. The test results show that the location of steel in the tube cross-section has a significant influence on its mechanical properties. The results obtained for the cold-formed YSt-355-FR structural steel suggest the necessary inclusion of proposed new strength reduction factors for the cold-formed steels and up-gradation in the strength reduction factors of hot-rolled steels in the relevant fire design standards. The use of yield strength at 2% strain (upto 500 °C) and at 1% strain (beyond 500 °C) yields optimum buckling strength of YSt-355-FR columns. The provisions mentioned in the EC3 safely predicted the buckling strength of the YSt-355-FR steel tube columns compared to that predicted by the finite element analysis. Important observations have been made in this study, which shall help designers and practitioners in designing steel structures using cold-formed steel tubular sections.