Steel Tubular Sections Research Articles

Experimental investigation on hollow-steel-tube columns with external confinements

Tubular steel members with slender cross-sections in compression are prone to local buckling. Different approaches, such as infilling concrete, installation of internal stiffeners and externally bonding fiber-reinforced polymer reinforcement, have been developed to retard the local buckling of steel tubular sections, and hence to improve the performance of tubular structures. In this study, a total of 35 circular hollow-steel-tube (HST) stub columns with both non-slender and slender cross-sections confined by different types of external confinements, namely steel ring, spiral and jacket confinements were tested in the experimental program. The uni-axial behavior of externally confined HST columns, including the failure mode, ultimate load-carrying capacity, stiffness and ductility, were studied and discussed. The enhancements in strength, stiffness and ductility of HST columns with different external confinements were assessed. The results indicated that the improvements on strength and stiffness of the confined HST columns were insignificant for columns with non-slender cross-sections and were considerable for columns with slender cross-sections, whilst the ductility of the HST columns was substantially enhanced by external confinements. Based on the results, equations for column ductility evaluation considering the effects of cross-section slenderness ratio, steel strength and external confinement, are proposed in this study, which are able to predict the column ductility for unconfined and externally confined HST columns.

Analysis of carbon fibre reinforced polymer wrapped square steel tubular sections under compression

This paper presents the Finite Element (FE) analysis of Square Hollow Steel (SHS) tubular sections externally wrapped with Carbon Fibre Reinforced Polymer (CFRP) strips under axial compressive load. CFRP sheets are used as strip form and the width of the strip is 50 mm. The spacing between the strips is considered as a constant of 20 mm and the numbers of layers are one, two and three in the horizontal direction. All the samples are subjected by axial compressive load till reached their ultimate failure load. From the test results, the failure style, axial load and displacement, Ultimate load and stress strain behaviour were compared with the control and each other. Finally a numerical analysis were designed for failure style, stress strain, ultimate load and axial displacement using ANSYS package and validated with the test results. FE modelling provided a suitable wrapping scheme for SHS tubular members.

Crushing strength of square hollow steel tubular sections externally jacketed by carbon fibre reinforced polymer strips

Square Hollow Steel (SHS) tubular sections have wide range of structural applications comprise of strength and ductility and therefore they are successfully performed in seismic regions. However they failed due to additional loads, faulty design and construction, severe environmental situation and corrosion. FRP technology provides better solution for the above mentioned problems compared to traditional methods. This paper presents the SHS tubular sections externally wrapped with CFRP sheets and subjected by axial crushing. Width and spacing of strips are kept constant and number of layers can be varied as one, two and three. After the crushing test, results were compared with one another and the wrapped specimen. Finally, failure pattern, stress-strain curve, axial crushing strength, load vs deformation curve and ductility were found from the test results and also suggested the optimum usage of CFRP strips for SHS strengthening.

Behaviour of hybrid fibre reinforced concrete-filled steel tubular beams and columns

ABSTRACT This paper presents the flexural performance of newly developed hybrid fiber reinforced concrete-filled steel tubular sections. The test parametres are fiber volume fraction and fiber hybridation ratio. Initially mechanical properties studied for 10 mono fiber reinforced concrete mixes using steel and Polypropylene fibres with 0.5%, 1.0%, 1.5%, 2.0% and 2.5% volume fraction. Based on the performance optimum fiber dosage was determined in each fiber, with the same volume fraction three different fiber hybridation was developed. Developed hybrid fiber reinforcement concrete, conventional concrete and optimum mono fiber reinforced concrete was used in the concrete-filled steel tubular beams and columns to determine the structural performance. The test results shows that, fiber reinforced concrete-filled steel tubular beams display significant improvement in the flexural performance.

Testing of hot-finished high strength steel SHS and RHS under combined compression and bending

Abstract An experimental investigation into the cross-sectional behaviour of hot-finished high strength steel tubular sections, to support the assessment and development of structural design guidance, is presented. Two grades of quenched and tempered high strength steel – S690 and S770 and eight cross-sections – seven square hollow sections (SHS) and one rectangular hollow section (RHS), covering a wide range of local slenderness, were examined. This test programme consisted of twelve tensile coupon tests, five stub column tests and 30 short beam-column tests, with various initial loading eccentricities employed to achieve a spectrum of compression and bending combinations. Local geometric imperfection measurements were carried out on each test specimen using 3D laser-scanning, and a rational approach to analysing the local imperfection distributions using the scanned data was subsequently proposed. Following the experimental study, the current Eurocode 3 cross-section design provisions were evaluated through comparisons with the results from the present research and additional results from the literature. The experimental results and findings from the present study provide a basis for the development of numerical models and the enhancement of existing design methods in the future.

Predictions of material properties in cold-rolled austenitic stainless steel tubular sections

Material properties in cold-rolled stainless steel members are significantly different from those in annealed sheets (e.g. considerable enhancement in 0.2% proof stress), which provides a potential to reduce the initial cost of stainless steel structures in the design stage. This study is aimed at proposing reasonable predictive formulas for the enhanced material properties in cold-rolled stainless steel tubular sections. A total of 130 tensile coupons were extracted from three types of material statuses (i.e. the coil, the circular hollow section and the square/rectangular hollow section) occurred in four cold-rolling production routes. Tensile coupon tests were then conducted to illustrate the change of material properties from coils to square/rectangular hollow sections (SHS/RHSs) as well as the detailed distributions of material properties in cross-sections. Based on test data, predictive formulas were developed for all material parameters in cold-rolled stainless steel hollow sections according to the “through thickness averaged plastic strain” method originally proposed by Gardner's group in Imperial College London. The predictions of the proposed formulas were evaluated using the test results in this study and in existing literature. Comparisons indicate that proposed models provide not only accurate predictions for the key material properties (e.g. the 0.2% proof stress, the 1% proof stress and the ultimate tensile strength), but also reasonable predictions for full-range stress-strain curves in cold-rolled stainless steel hollow sections. The predictions of the proposed models can be used in finite element analysis and advanced design methods for cold-rolled stainless steel hollow sections.

Behavior of Octagonal High-Strength Steel Tubular Stub Columns

AbstractThis paper investigates the behavior of octagonal high-strength steel tubular cross sections under axial compression. Experimental investigations were conducted on cross sections with three...

Mechanical properties and cross-sectional behavior of additively manufactured high strength steel tubular sections

Abstract Additive manufacturing, commonly known as 3D printing, is an evolutional technology in the manufacturing industry. This technology has already been embraced by different industries, such as aerospace and biomedical engineering, and the recent advance in this technology has generated a vast of societal excitement for its future. Despite the exciting prospect of its application in civil engineering, additive manufacturing technology is still at a perceived stage for construction industry. The benefits and potential in construction industry are rarely known in the field at this stage. This paper aims to investigate the mechanical properties and structural performance of additively manufactured high strength steel tubular sections at the cross-sectional level through experimental program. The specimens were additively manufactured from H13 steel powder by selective laser melting (SLM) with three different scanning patterns, where the typical yield strength (0.2% proof stress) of the conventionally manufactured H13 steel is around 1650 MPa. The test program comprised tensile coupon tests, compression coupon tests, hardness tests, microstructural characterization as well as geometric imperfection measurements and stub column tests. The anisotropy on mechanical properties was examined through tensile coupon tests in both longitudinal and transverse directions. Compression coupon tests were also conducted to investigate the differential strength of material in tension and compression. The influences of scanning patterns on mechanical properties and structural behavior of as-printed high strength steel tubular sections stub columns were also investigated. The test results were used to assess the applicability of existing design provisions in the American Specification, Australian and New Zealand Standard as well as European Code that originally developed for conventionally produced hot-rolled and cold-formed steel tubular sections to the additively manufactured high strength steel tubular non-slender sections in this study.

The continuous strength method for the design of high strength steel tubular sections in bending

The continuous strength method (CSM) adopts base curves which relate the deformation capacity to its overall cross-section slenderness to take into account the element interaction and employs elastic, linear hardening material models to exploit the strength enhancement from strain hardening. This paper extends the CSM for structural design of hot-finished and cold-formed high strength steel tubular sections under bending. Results of 146 tests in the literature were compiled and a parametric study on 660 high strength steel tubular beams was conducted using validated finite element models. Base curves and resistance functions were proposed for non-slender and slender high strength steel circular hollow sections (CHS), elliptical hollow sections (EHS), square hollow sections (SHS) and rectangular hollow sections (RHS). Bi-linear and tri-linear material models were adopted for cold-formed and hot-finished steel tubular sections, respectively. Experimental and numerical results of 806 tubular beams were used to assess the proposed CSM, the direct strength method (DSM) and codified design methods. The resistance prediction of the proposed CSM is more accurate and less scattered.

Design of CFRP-strengthened stainless steel tubular sections subjected to web crippling

ABSTRACT This paper presents a nonlinear finite element analysis and also depicts the design of stainless steel hollow square and rectangular sections strengthened by CFRP under web crippling loading configurations. Current design rules do not provide sufficient information for predicting the performance of CFRP-strengthened stainless steel hollow sections against web crippling. To develop a new comprehensive design rule, this research provided a nonlinear finite element analysis (FEA) based on a series of laboratory tests. The tests were conducted subjected to four different loading conditions, end-two-flange (ETF), end-one-flange (EOF) interior-two-flange (ITF) and interior-one-flange (IOF). Geometric and material nonlinear finite-element models were developed, substantiated by the experimental results. The traction separation law was used to simulate the debonding mechanism between the CFRP plate and stainless steel tubes in the nonlinear analysis process for the cohesive zone modeling. The finite-element models explicated well the behavior of CFRP strengthening and closely predicted the ultimate load-carrying capacity, web-crippling failure modes, as well as web-deformation curves of the tested sections. A parametric investigation was conducted using the verified finite element models for tubular sections with different dimensions. For CFRP enhancement of stainless steel members, the validated finite element models has been demonstrated as an constructive and time-saving method to determine the strengths of web crippling. The proposed design equation predictions also agreed well with the tests and numerical results. The web crippling strengths can be predicted effectively by the proposed design equation for CFRP enrichment stainless steel hollow sections against web crippling loading configurations.

Analysis of Mechanical and Metallurgical Properties of Friction Welded ASTM A106Gr.B Carbon Steel Pipe Joints by Varying Upset Pressures

Friction welding is one of the most common methods employed in the joining of carbon and alloy steel tubular sections. In the present work, the analysis of the effect of upset pressure on mechanical and metallurgical properties of friction welded ASTM A 106 Gr. B low carbon steel pipes has been investigated. The test joints were made using continuous drive welding machine with upset pressures of 5 MPa to 8 MPa and evaluated for microstructure, hardness, tensile strength and impact toughness. The weld joints exhibited mostly ferrite and pearlite microstructure in both fully plastically deformed zone (FPDZ), partially deformed zone (PDZ) on the either side of the weld interface and a distinct dynamically recrystallized ferrite pearlite microstructure was observed in the FPDZ at the weld centre line. Better tensile properties were observed in case of the joints made with upset pressure of 6.4 MPa. It is observed that the weld region is stronger than base metal and the hardness has increased with the increase in the upset pressure. Marginal reduction in the toughness was noted with the increase in the upset pressure.

Local and post-local buckling of normal/high strength steel sections with concrete infill

Steel sections in steel-concrete composite columns have been proofed to be less susceptible to local buckling and have higher capacity than bare steel columns, attributed to the internal restraints provided by the infilled concrete. This article presents a theoretical study concerning the local and post-local buckling of fabricated normal and high strength steel sections filled with concrete, including concrete filled steel tubular (CFST) sections and partially encased composite (PEC) sections. A nonlinear finite element (FE) model was established and validated to simulate the behavior of steel plates in contact with concrete, with both geometric imperfections and residual stresses explicitly incorporated. This model was subsequently applied in a parametric study to investigate the effects of several critical factors on the local buckling behavior of box and I steel sections. Based on the available test and FE results, new design formulas were proposed to predict the local buckling and post-buckling ultimate strengths of concrete-restrained steel box and I sections, taking into consideration high material strengths, residual stresses and geometric imperfections. The enhancement of strength due to the presence of concrete infill was confirmed through a comparison with the post-buckling strength of bare steel sections. Recommendations were also made for design purpose based on the formulas proposed.

Ultimate Axial Strength of Concrete‐Filled Double Skin Steel Tubular Column Sections

This study aims at proposing a new model for evaluating the ultimate axial strength of concrete‐filled double skin steel tubular (CFDST) composite columns. For this, a total of 103 experimental data regarding the ultimate strength of CFDST columns under axial loading were collected from the previous studies in the literature. All CFDST columns consist of two steel tubes being outer and inner circular hollow section. The model presented herein was developed by using gene expression programming. For this, the yield strength, diameter, and thickness of both outer and inner steel tubes, the compressive strength of annulus concrete, the length of the specimen, and the ultimate axial strength of the columns were utilized as the parameters. Assessment of the obtained results indicated that the generated model had a good performance compared to the existing models by the previous researchers and the equations specified in the design codes. The high value of R2 and narrow ranged fluctuation of the estimation error for the ultimate axial strength of the CFDST columns were also achieved through the proposed model.

Post-fire mechanical properties of YSt-310 cold-formed steel tubular sections

An experimental programme to study the residual mechanical strength of Tata Structura-YSt 310 cold-formed steel square and rectangular tubular sections (conforming to Indian Standard 4923) after being exposed to elevated temperature is described in this paper. First, the coupon specimens extracted from the flat regions are exposed to pre-determined elevated temperature in the range ~ 300–800 °C, and then the residual mechanical properties and hardness value were estimated at ambient temperature after natural air cooling. The results from the experimental programme are reported in this paper in the form of post-firestress-strain curves and associated basic material properties (e.g. elastic modulus, proof stresses, tensile strength, percentage elongation at fracture, Ramberg-Osgood material parameters etc.) as well as surface hardness values. The test results showed that most post-fire mechanical properties are appreciably different from ambient temperature material properties when exposed to a temperature higher than ~400 °C; whilst elastic modulus appears to remain unaffected even when the exposed temperature is up to ~800 °C. A near linear relationship of post-fire material strengths and hardness value was observed. Two sets empirical equations are proposed separately to predict the residual post-fire reduction factors based on the i)current experimental results of Tata Structura-YSt 310 cold-formed steel, and ii) cold-formed steel of various grades presently available in the literatures.

Experimental and Numerical Investigations of Bolted CFST Beams–CFST Columns Connections

The effectiveness of concrete-filled steel tubular (CFST) sections as compression and flexural members has been investigated by many authors. The combined utilization of CFST columns and steel beams has increased in composite building construction in recent years, but combined use of CFST columns and CFST beams is still unexplored. To explore their potential as part of CFST frame structures, two types of connections using extended end plate and seat angle are proposed for exterior joints of CFST beams and CFST columns. The performance of the proposed bolted connections subjected to static loads has been investigated by executing an experimental program involving eight specimens of exterior beam-to-column joints subjected to monotonically increasing load applied at the free end of the beam. The performance is appraised in terms of load deformation behaviour and failure modes of joints with varying test parameters like the beam section type, length and diameter of bolts. Finite element analysis for the applied load has been performed using ATENA-3D software, and the behaviour of the connections is investigated. The FE simulation results are compared with experimental test data to verify the FE model.

Web crippling of lean duplex stainless steel tubular sections under concentrated end bearing loads

A series of tests was conducted to investigate the web crippling behaviour of cold-formed lean duplex stainless steel (LDSS) tubular sections. The LDSS had two grades, including EN 1.4062 and EN 1.4162. The tests were performed under three different conditions of concentrated end bearing loads, namely, the loading conditions of End-One-Flange (EOF), the End-Two-Flange (ETF) and end loading (EL). The loading conditions of EOF and ETF are specified in the American and Australian/New Zealand cold-formed stainless steel design specifications, while the loading condition of EL simulated the floor joist members positioned on a solid foundation under concentrated end bearing load. The test specimens were mainly failed by web crippling. The test strengths were compared with the predicted strengths that calculated by the stainless steel design specifications, including the American Society of Civil Engineers (ASCE) Specification, Australian/New Zealand Standard (AS/NZS) and European Code (EC). In addition, the web crippling strengths predicted by the North American Specification (NAS) for cold-formed carbon steel structures and using the design equations proposed in the literature for cold-formed duplex stainless steel tubular sections were also compared with the test strengths. It was found that the predicted strengths calculated by the ASCE, AS/NZS and EC specifications are conservative and reliable for LDSS sections under the three different concentrated end bearing loads. The predictions by NAS and proposed equations in the literature are generally less conservative compared with those by ASCE, AS/NZS and EC. However, the predictions by NAS are found to be unconservative and not reliable for the loading condition of ETF.

Design of cold-formed high strength steel tubular sections undergoing web crippling

Design of cold-formed high strength steel (HSS) tubular sections undergoing web crippling is examined in this study. Finite element (FE) models were developed and validated against available test results, showing the capability of replicating the experimental web crippling strengths, failure modes and load-web deformation histories. On validation of the FE models, an extensive parametric study comprised of 224 FE analyses was performed. The web crippling provisions in the current North American Specification, Australian/New Zealand Standard and European Code for cold-formed steel structures were assessed. The web crippling strengths obtained from the numerical investigation together with available experimental data from the literature were compared with the nominal strengths derived from the aforementioned specifications. Overall, the comparisons showed that the nominal strengths predicted by the existing codified provisions are either unconservative or overly conservative. Hence, improved design rules are proposed for cold-formed HSS tubular sections undergoing web crippling by means of modified unified equation and Direct Strength Method. The reliability of the modified design rules has been proven through reliability analysis.

Flexural behavior of lightweight concrete and self-compacting concrete-filled steel tube beams

The study presents a comparative experimental analysis of the flexural behavior of lightweight concrete and self-compacting concrete filled square steel tube beams subjected to pure bending. A total of 20 specimens including eight lightweight concrete-filled steel tube (LWCFST) beams, eight self-compacting concrete-filled steel tube (SCCFST) beams, and four hollow steel tubes were tested. The main parameters varied during the experiment include (1) type of concrete core, lightweight concrete (LWC), and self-compacting concrete (SCC); (2) width to thickness ratio; and (3) confinement factor (ξ). The flexural capacities, flexural stiffness, ductility, failure modes, deflection curves, and bending moment versus mid-span deflection curves were examined. Several performance indexes were used to discuss the flexural strength, stiffness, and ductility of the tested beams. The test results revealed that LWC and SCC significantly improved the overall flexural behavior of square hollow steel tubular sections. The results indicated improvements in flexural strength, stiffness, and ductility. Furthermore, a comparison was performed, and the findings indicated that LWCFST beams exhibit increased flexural stiffness, comparable moment resistance, and lower ductility when compared to SCCFST beams. The moment capacities and flexural stiffness were compared with the predicted values by using various design codes, and the comparisons indicated that all the design codes are conservative with respect to the estimation of the moment capacity. However, all the design codes are not conservative with respect to the prediction of the serviceability level flexural stiffness. The test results and comparisons motivate application of LWCFST and SCCFST beams as a potential alternative for normal weight CFST beams.

Investigations on cold-forming effect of cold-drawn duplex stainless steel tubular sections

The cold-drawing process is currently a significant way of manufacturing cold-formed structural tubular sections at room temperature. Furthermore, cold-drawing is more suitable for forming thick-walled sections with large dimensions than cold-rolling. Plastic deformation experienced during section forming causes increases in the mechanical properties and it also induces residual stresses in the cold-formed cross sections. This paper experimentally examined residual and material stress distributions in two types of cold-drawn tubular sections - three Circular Hollow Sections (CHS) and three Square Hollow Sections (SHS), and material-duplex (S22053) stainless steel. Based on the experimental findings, strength enhancement in CHS was not obvious owing to annealing treatment, removing cold work and increasing ductility. In this case, transverse bending residual stresses in CHS were only considered due to cold-forming effect. The residual stress distribution patterns including longitudinal and transverse stresses and predictive models for enhanced strength of the flat face of cold-drawn duplex stainless steel square hollow sections were developed. Comparisons of the predictions and the test data show that the proposed models were in good accuracy.

Design of austenitic and duplex stainless steel SHS and RHS beam-columns

A finite element analysis and design of austenitic and duplex stainless steel tubular section beam-columns is presented in this paper. The nonlinear finite element model was verified against experimental results of stainless steel tubular section beam-columns and beams. In this study, square and rectangular hollow sections were investigated. It was shown that the finite element model closely predicted the ultimate loads and failure modes of the tested beam-columns and beams. Hence, the finite element model was used for an extensive parametric study. The axial compressive strengths of the beam-column specimens predicted by the finite element analysis are compared with the design strengths calculated using the linear interaction equation and direct strength method. Reliability analysis was performed to assess the reliability of these design rules. It is shown that these design rules generally provide accurate and reliable predictions for stainless steel tubular section beam-columns. Design recommendations for linear interaction equation and the direct strength methods are proposed for stainless steel SHS and RHS beam-columns.