Steel Rectangular Hollow Sections Research Articles

Effect of web holes on web crippling capacity of rectangular hollow steel sections under two flange loadings

This paper presents experimental and numerical investigations on web crippling behavior of hot rolled rectangular hollow section (RHS) with web holes. A total of 20 rectangular hollow sections, subjected to interior-two-flange (ITF) and end-two-flange (ETF) loading conditions undergoing web crippling, were experimentally tested. The experimental program was designed to obtain web crippling of specimen having slenderness (h/t) value of 21.32, by varying size and offset distance of web holes under two flange loading conditions. Finite element models of experimentally tested beams were developed, and results of finite element analysis showed good agreement with experimental results. A parametric study was then conducted using finite element analysis on different cross section sizes, to demonstrate the effect of size and position of web holes on web crippling capacity of rectangular hollow sections. It was demonstrated that ratio of diameter of web hole to the depth of flat portion of web (a/h) and ratio of offset distance of web hole to the flat portion of web (x/h) are the primary parameters affecting the web crippling strength. Design recommendations in the form of reduction factors for both loading conditions are proposed, that are conservative to both experimental and finite element results. To assess the reliability level of design recommendations, reliability analyses were undertaken.

Localized loading behavior of cold-formed stainless steel RHS under interior-one-flange load case at elevated temperatures

The localized loading behavior of cold-formed stainless steel (CFSS) rectangular hollow section (RHS) members at elevated temperatures is investigated in this paper. Fifteen localized loading tests conducted at various temperatures up to 800 °C were reported. The tests were carried out under the Interior-One-Flange (IOF) load case as specified in American Specification for the design of cold-formed stainless steel structural members. Tensile coupon tests were performed to obtain the material properties of the CFSS RHS at various temperatures. Detailed information on dimensions, temperature histories, failure modes, load-deformation curves, localized loading capacities of specimens at various temperatures were presented. In addition, a numerical investigation was supplemented, where a total of 192 finite element (FE) analyses were undertaken after validation of developed FE model against the elevated-temperature test results. The influence of various parameters on the localized loading capacities of CFSS RHS at different temperatures under IOF load case was revealed. The obtained results were utilized to assess the applicability of the localized loading design provision for CFSS RHS under IOF load case codified in the American Specification to elevated temperature conditions. Moreover, the results were also compared with predictions based on existing design rules in literatures for cold-formed RHS at elevated temperatures. Furthermore, reliability analyses were carried out to assess the reliability levels of the assessed design methods. It is shown that the existing design rules can generally provide conservative and reliable predictions of the localized loading capacities for the CFSS RHS under IOF load case at elevated temperatures.

Stiffness of Loaded Face of Steel Rectangular Hollow Section Columns with and without Concrete Infill in Beam-column Endplate Connections

This paper presents a new analytical approach for calculating the stiffness of the loaded face of a rectangular hollow section RHS column in beam-column connections with and without concrete infill, as well as with flush and extended endplates, to determine the behavior curve of these types of connections. The approach, based on Eurocode 03's component method, offers efficient analytical formulas for accurately determining the loaded face's stiffness. A comparison with existing methods demonstrates its remarkable simplicity and efficiency, allowing a simple beam model to represent the RHS column's behavior with all relevant parameters considered. Comparison of the new approach to existing ones from the literature demonstrates their reliability and efficiency. Furthermore, when compared to 32 experimental tests presenting nearly the entire range of probable connection configurations, as well as attachment techniques commonly used in construction practice, the margin of error does not exceed 12 percent on average and a maximum of less than 25 percent.

Cross-section behaviour and capacity of cold-formed austenitic stainless steel flat-oval hollow sections under combined compression and bending

Flat-oval hollow section is composed of two semi-circular elements and two flat elements, with the semi-circular elements (exposed to wave and wind) offering a low level of hydrodynamic and aerodynamic drag and the flat elements facilitating connections with other members perpendicular to the wave and wind directions. This paper presents an experimental and numerical study of the cross-section behaviour and resistance of cold-formed austenitic stainless steel flat-oval hollow section stub columns under combined compression and bending. An experimental programme, including initial local geometric imperfection measurements and ten major-axis and minor-axis eccentric compression tests, was firstly carried out, with the test setups, procedures and results fully reported. Following the experimental programme, a numerical modelling programme was performed, with finite element models developed and validated against the eccentric compression test results and then used to conduct parametric studies to generate additional numerical data. Based on the test and numerical results, the relevant codified design interaction curves for cold-formed austenitic stainless steel rectangular hollow sections were evaluated for the applicability to their flat-oval hollow section counterparts. It was found from the evaluation results that the codified design interaction curves led to inaccurate resistance predictions, mainly due to the conservative end points (i.e. cross-section resistances under pure compression and pure bending) and inefficient shapes. Finally, a new design interaction curve was proposed through the use of more accurate end points and more efficient shape and offered more accurate and consistent resistance predictions for cold-formed austenitic stainless steel flat-oval hollow sections under combined loading than the codified design interaction curves.

Experimental investigation on cold-formed steel hollow sections with moderate heat treatment under combined compression and cyclic lateral loads

This paper presents an experimental investigation on cold-formed steel rectangular and square hollow sections (RHSs and SHSs) with subsequent heat-treatment under combined compression and cyclic lateral loads. A total of 25 specimens designed with different parameters, including slenderness ratios (b/t and d/t) and axial load ratio (n) ranging from 0 to 0.5 were tested. Material tests were carried out to confirm the material ductility requirements stated in Eurocode being reached. Failure modes, moment-rotation curves, secant stiffness, energy dissipation and plastic hinge length presented were analysed. In addition, deformation capacity was evaluated in terms of maximum and ultimate rotations. The comparison results between plastic rotation limits proposed by design codes and the test results indicate that AISC 341-16 is more suitable for the design of cold formed hollow sections with moderate heat treatment under this investigation, though the recommended reduction factor of axial load might be conservative.

Experimental and numerical investigations of austenitic stainless steel semi-oval hollow sections under combined compression and bending

Semi-oval hollow section is an innovative cross-section profile, including one semi-circular flange, one flat flange and two flat webs. While the semi-circular flange (exposed to fluid or wind) offers a low level of hydrodynamic or aerodynamic drag, the flat elements facilitate connections with other members. This paper presents experimental and numerical investigations into the local buckling behaviour and resistances of austenitic stainless steel semi-oval hollow sections under combined compression and bending. A testing programme was firstly conducted and included initial local geometric imperfection measurements and ten eccentric compression tests. In conjunction with the testing programme, a numerical modelling programme was performed, where finite element models were developed to validate against the test results and conduct parametric studies for expanding the test data pool over a wider range of cross-section dimensions and loading combinations. The obtained test and numerical data were used to evaluate the applicability of the relevant design interaction curves for austenitic stainless steel rectangular hollow sections, as prescribed in the European code and American specification, to austenitic stainless steel semi-oval hollow sections. On the basis of the evaluation results, the codified design interaction curves were found to provide conservative resistance predictions. Finally, an improved design interaction curve, with more accurate end points and suitable shape, was developed and led to more accurate and consistent resistance predictions for austenitic stainless steel semi-oval hollow sections under combined compression and bending.

Residual stresses of MAG-welded ultrahigh-strength steel rectangular hollow sections

Residual stresses are an important factor in the performance and stability of welded structures. This study investigates the characteristics and significance of residual stresses in MAG-welded ultrahigh-strength steel rectangular hollow sections. The research incorporates comprehensive X-ray diffraction residual stress measurements, electron backscatter diffraction analysis, statistical analyses, and finite element method simulations to provide valuable insights into the behaviour of welding residual stresses. The results reveal clear microstructural variations between the cold-formed corner and the flat side of the rectangular hollow section caused by welding heat input, emphasizing the need to consider these variations in residual stress assessments. Furthermore, the study examines the dependence of residual stresses on the steel grade, with higher strength steel exhibiting compressive stresses and lower strength materials experiencing tensile stresses in corner areas. Statistical analysis indicates that welding sequence and direction have negligible effects when applying the employed welding sequence. In any case, higher heat input leads to significantly larger residual stresses. Finally, the study presents a novel analytical model based on validated finite element simulations to predict the maximum variation of residual stresses depending on welding heat input. The findings provide valuable insights into the significance of welding residual stresses and their predictability. The comprehensive measurements, simulations and proposed models contributes to a better understanding of residual stress phenomena, facilitating the development of reliable design guidelines for welded structures in various engineering applications.

Experimental programme on austenitic stainless steel RHS members subjected to monotonic and cyclic bending

Stainless steel is a corrosion resistant iron alloy with great potential in structural engineering due to its excellent mechanical features, durability and aesthetic properties. Since most of the existing research has concerned the behaviour of the material, the response of individual structural members, or the performance of simple structural systems under monotonic loading, one of the challenges that remains is the evaluation of the cyclic performance of members to promote its use in seismic design and exploit the excellent ductility and strain hardening properties of this material. For this reason, an experimental programme on austenitic stainless steel Rectangular Hollow Section (RHS) specimens was carried out at the Department of Civil Engineering of the Università degli Studi di Salerno in collaboration with the Universitat Politècnica de Catalunya. A total of eight RHS specimens were tested around the minor axis under both monotonic (three specimens) and cyclic (five specimens) loading, in an experimental set-up that followed a cantilever scheme. The main purpose of this study was to acquire information on the cyclic performance of austenitic steel structural members, focusing on the comparison between monotonic and cyclic behaviours. The outcomes of the tests included the load–displacement and the moment–rotation curves, the energy dissipation capacity, and the evaluation of the key rotation capacities of the members. The reported data are essential to enhance the still scarce research on the seismic behaviour of stainless steel structures.

Analysis and Experiment on the Welding Temperature Field of Multi-Layer and Multi-Pass for RHS–RHS Y-Connections

The temperature measuring instrument was utilized to monitor the welding temperature field at designated points along steel rectangular hollow sections (RHSs) during welding. A total of 32 temperature monitoring points were established on the four surfaces of the RHS branch. Additionally, the welding process was simulated using finite element software to calculate the temperature distribution. The calculated temperature results were then compared with the experimental results obtained from the temperature measuring instrument. The relative errors between the numerical simulation and the experimental temperature results remained within 10%, indicating a reasonable agreement between the two. Once the temperature field was determined, it was used as an input load to calculate the welding residual stress. The longitudinal and transverse residual stresses were analyzed for two paths on the four surfaces of the RHS-to-RHS Y-shaped connection branch. By analyzing the residual stresses, it is possible to evaluate the structural integrity and performance of the welded RHS connection. The analysis process in this paper is crucial for ensuring the safety and reliability of tubular steel structure projects.

Investigating the behavior of hollow steel section beam under repetitive transverse impact loading

When a load is exerted on a structural element several times, it is called repetitive loading. This type of loading causes more damage to structural elements than monotonic loading. This paper presents the effects of repetitive transverse impact loading on the weak axis of rectangular hollow steel section beam. For this purpose, three simply supported beams were tested with a constant drop weight of 75 kg and three different heights (400 mm, 800 mm and 1200 mm). Transverse impact load was exerted on each specimen 3 times repeatedly. In the numerical studies, finite element models of all specimens were developed using ABAQUS finite element analysis software. In order to obtain reliable numerical models, finite element models were verified using the experimental data. To investigate the effects of repetitive transverse impact loading on hollow section steel beam, parameters such as displacement, reaction forces, stress distributions and out of plane plastic denting were evaluated comparatively. The obtained results showed that, when the height value is increased twice as the initial height in test series RIA and RIB, the displacement value increased by 57% in the first hit, 68% in the second hit and 79 % in the third hit. Thus, it seems that the increase in the displacement value due to the increase in the damage of subsequent hits is not linear, but rather logarithmic. Finally, it was understood that with increase in the plastic deformation and displacement occurring in an element subjected to repeated impact loading, a decrement occurs in the reaction force transferred to the supports.

Local buckling response and design of stainless steel hollow sections at elevated temperatures

AbstractThe structural behaviour and design of stainless steel hollow sections in fire, including stainless steel (i) circular hollow sections (CHS), (ii) elliptical hollow sections (EHS), (iii) square hollow sections (SHS) and (iv) rectangular hollow sections (RHS), are explored in this paper. Shell finite element models of stainless steel CHS, EHS, SHS and RHS able to replicate their structural response at elevated temperatures are created. Numerical parametric studies are performed on cold‐formed and hot‐rolled austenitic, duplex and ferritic stainless steel CHS, EHS, SHS and RHS subjected to (i) pure compression, (ii) pure bending, (iii) combined axial compression and bending and (iv) combined bending and shear in fire, covering different cross‐section slendernesses and elevated temperature levels. Calibrated against the benchmark structural performance data obtained from the numerical parametric studies, the new design proposals for predicting the ultimate resistances of stainless steel CHS, EHS, SHS and RHS in fire put forward in Quan and Kucukler [1,2] are set out. It is demonstrated that relative to the design recommendations provided in the European structural steel fire design standard EN 1993‐1‐2, the proposed cross‐section design methods provide more accurate and safe‐sided ultimate resistance predictions for stainless steel CHS, EHS, SHS and RHS at elevated temperatures.

The cross-sectional resistance of square and rectangular hollow steel sections loaded by bending moment and shear force

This paper presents an evaluation of the design rules for the bending moment–shear force (M−V) interaction of cold- and hot-formed square, and rectangular hollow steel sections (SHS & RHS). More specifically, the design rules, as provided by EN1993-1-1 regarding RHS and SHS of section class 1 and 2 are covered for the steel grades S235 up to and including S460. A 4-point bending test was simulated by means of a finite element model, which was validated on the basis of experimental tests from existing literature. A parametric study was performed and numerical M−V interaction results were compared to the provisions in EN1993-1-1. This comparison indicates that the current design rules in EN1993-1-1 regarding M−V interaction are conservative and overestimate the reduction of the bending resistance due to the presence of shear. Alternative design rules for the shear area and M−V interaction of RHS and SHS are proposed and evaluated by means of a statistical assessment procedure based on existing literature and EN1990-1-1. Both newly developed design rules are shown to ensure an adequate reliability level when a partial safety factor equal to 1 is used.

Lateral-torsional buckling performance of high strength steel rectangular hollow section beam-columns

A new approach namely Plate-Beam theory was employed to perform the investigation into the lateral torsional buckling (LTB) performance of high strength steel (HSS) rectangular hollow section (RHS) beam-columns. Firstly, the total strain energy corresponding to the LTB failure mode of the beam-columns was established, and then the equilibrium differential equation was developed, through the variation of energy functional. Based on the Plate-Beam theory, the equivalent restrained torsional rigidity (warpage constant) that can simultaneously accounted for the secondary warping effect was derived, and the formulation process did not involve any sectoral coordinate operation. The deducing process of the total strain energy of RHS beam-columns was further discussed and recommended to describe the torsion performance of composite and irregular thin-walled members. Based on the FE program verified against test data and theoretical solution, the accuracy of the provisions of HSS RHS beam-columns given in Eurocode3 and GB50017-2017 was assessed. The comparison of numerical program against codified design provisions revealed that the resistance prediction in Eurocode3 was still serviceable for HSS RHS beam-columns, in conjunction with the torsional rigidity according to the Plate-Beam theory.

Investigation of Bending Behaviors of GFRP-Strengthened Steel RHS Profiles with Experimental and Numerical Models

The contribution of GFRP (glass fiber reinforced polymer) fabric to the bending behavior of steel RHS (rectangular hollow section) beams was investigated by experimental and numerical studies. In the first part of the study, small-scale RHS profiles were strengthened with GFRP fabrics in ten different configurations in the experimental study. The bending behavior of the profiles was determined by three-point bending tests, and the best strengthening configuration was decided. The numerical models were verified with the experimental results. In the second part, real-size RHS beams were strengthened with the optimum strengthening configuration. In the results of the study, it was determined that the U-shaped strengthening provided the maximum contribution to the RHS beams bending behavior. The minimum GFRP size to be used in strengthening is important, as an insufficient GFRP length leads to GFRP failure, and the number of layers should be increased for more load capacity. A total of 25% of the net beam span was determined to be the minimum GRFP length. In full-size beams, a double-layer GFRP increased the maximum load-bearing capacity by 7%. Formulas were obtained to determine the contribution of single and double-layered U-shaped GFRP to the shape factors of the RHS. With the formulations, the plastic moment capacity can be determined.

Influence of Strain Hardening on Sectional Capacities of Cold-Formed Rectangular Hollow Steel Sections

Cold-formed steel members have been widely used in structural applications and have been included in current design standards. These current standards have been established on the basis of the idealized plastic behavior of material properties, whereas the rounded stress-strain curves are obtained with the significant strain hardening due to cold-forming processes. The predictions from the current standards become overly conservative compared to the actual strengths of cold-formed steel sections. A new design method named the Continuous Strength Method, therefore, has been proposed and developed to provide more accurate strength predictions of this structural type with the consideration of strain hardening effects. In this paper, this method is applied to investigate the sectional capacities of cold-formed rectangular hollow steel sections under compression or bending with the variation of ultimate strengths compared to the predicted strengths using the European Code.

Behaviour of Cold Formed Steel Rectangular Hollow Section Filled with Concrete under Cyclic Lateral Loadwith Constant High Axial Compression

This paper presents an experimental investigation of Rectangular Concrete Filled Steel Tube (RCFST) sections subjected to cyclic lateral load combined with constant high axial compression. A total of eight RCFST columns with different combinations of width to thickness ratio, slenderness ratio and axial compression ratio were tested. The constant axial compressive load on the test columns was 60% and 80% of its axial load carrying capacity. Failure modes such as local buckling and rupture of steel tube were observed from experiments during strength degradation after reaching maximum lateral load. From the experimental results, envelope curves were obtained by joining the locus of extremities of the load-displacement hysteresis loops. Seismic parameters such as strength, stiffness, ductility, and energy dissipation capacity were discussed based on experimental results.

Fracture simulation of welded RHS X-joints using GTN damage model

A welded rectangular hollow section (RHS) X-joint exposed to tension loading has three typical fracture-related failure modes: Punching shear failure (PSF), Brace failure (BF), and Chord side wall failure (CSWF). Prediction of these failure modes by finite element (FE) simulations requires modelling of the material damage. An appropriate damage model accurately predicts the behaviour of the fracture zone and provides the necessary information to improve design rules for welded high-strength steel (HSS) RHS X-joints based on parametric studies using validated model. In this paper, the parameters of the Gurson-Tvergaard-Needleman (GTN) damage model are calibrated for the base material (BM) and the heat-affected zone (HAZ) of butt-welded cold-formed RHS connections, no fracture appeared in the weld. A computational homogenisation analysis is carried out using representative volume element (RVE) models to calibrate the pressure-dependent yield surface parameters of the GTN damage model, considering the different combinations of the accumulated initial hardening strain and the void volume fraction (VVF) due to a varying stress triaxiality. The critical and final VVFs are calibrated against tensile coupon tests. Finally, the GTN damage models calibrated for BM and HAZ are used in the fracture simulation of nine welded cold-formed RHS X-joints in monotonic tension. The FE model successfully predicts the experimental load-displacement relationships and fractured zone, indicating the calibrated GTN models could effectively be used in parametric study of welded cold-formed RHS X-joints. Finally, possible improvements to the used FE model are outlined for future studies.

Flexural behaviour of cold-formed steel square and rectangular hollow sections with moderate heat-treatment

This paper discusses the flexural behaviour of cold-formed square and rectangular hollow steel sections (SHSs and RHSs) with subsequent heat-treatment through experimental and numerical investigations. Firstly, an experimental programme comprising tensile coupon tests on flat and corner regions and three-point bending beam tests were conducted. A total of 12 specimens were tested under monotonic bending loads, covering a variety of section slenderness. Failure modes, moment-rotation curves and plastic hinge lengths have been evaluated highlighting the effect of the web-flange interaction on rotation capacity. Successively, experimental results were combined with numerical FE results to assess the corresponding moment and deformation capacities. Current cross-section classification limits given in Eurocode 3 and AISC 360–16 were assessed and new limits has been proposed.

Investigations of the through‐thickness residual stress distribution during the partial heating roll forming process of square and rectangular hollow steel sections

AbstractWith the growing demand for rectangular and square hollow steel sections in the last few decades, the cold roll forming process has become a widely acknowledged manufacturing method. However, the residual stress generated during the roll forming process is one of the primary concerns on roll‐formed products. One of the leading sources of residual stress is the severe plastic deformation that sheet metal experiences. It is well‐known that residual stress significantly affects the product's service life. In this regard, several researchers have conducted numerical and experimental investigations of residual stress distributions on roll‐formed steel sections. However, most of the studies found in the literature have been confined to the measurement of residual surface stresses. On the other hand, experimental studies conducted on fatigue and load‐carrying capacity of hollow structural steels have shown that there is indeed a simple relation between the through‐thickness residual stress distributions and mechanical properties of structures. Thus, this article employed a proper numerical modeling procedure using LS‐DYNA's finite element code to explore through‐thickness residual stress distributions generated during the roll forming process of rectangular and square hollow steel sections from different material grades. Moreover, a small‐scale parametric study was conducted to explore the effects of the partial heating roll forming method on through‐the‐thickness residual stress distributions.

Rotation capacity of cold-formed stainless steel RHS beams under cyclic loading

Stainless steel is a structural material with great potential in seismic design due to its ductile and strain hardening characteristics. However, no specific seismic design provisions exist for stainless steel, despite the remarkable differences with carbon steel. Moreover, research on the behaviour of stainless steel under cyclic conditions is scarce, not allowing designers to rely on accurate capacity models able to catch the actual member ductility under seismic excitation. Hence, the aim of this paper is to fill this lack and to provide simple provisions to estimate the total and stable part of the rotation capacity of stainless steel members with rectangular hollow section (RHS). A numerical study on 120 austenitic, ferritic and duplex beams under cyclic loading was performed following the ANSI/AISC 341 loading protocol. From the resulting skeleton curves, information on the ultimate strength and ductility (total and stable parts of the rotation capacity) were extracted. It was found that the ultimate bending moment resistance of RHS stainless steel beams under cyclic loading is accurately predicted by the Continuous Strength Method moment capacity, and that the rotation capacities can be related to the local slenderness by power functions calibrated from the numerical results. Finally, a tri-linear model that describes the full moment-rotation curves of stainless steel beams under cyclic loading is proposed using the calibrated equations, showing a good agreement with numerical moment-rotation curves, and which can be implemented in design software to define the behaviour of concentrated plasticity hinges.