Tubular Sections Research Articles

Design of cold-formed high strength steel square and rectangular hollow section beam–columns

Cold-formed high strength steel (CFHSS) square and rectangular hollow section (SHS and RHS) beam–columns were investigated in this study with an objective to evaluate the applicability of existing design rules given in American, Australian and European codes for SHS and RHS beam–columns of S700, S900 and S1100 steel grades, and subsequently, provide economical and reliable design rule for CFHSS SHS and RHS beam–columns. A comprehensive numerical investigation was performed in this study, where the values of flat width-to-thickness ratio of the tubular sections ranged from 7.5 to 96. The constitutive model developed for CFHSS tubular members was used in the numerical investigation. Global and local geometric imperfections were also included in the numerical models. In total, 465 data were compared with the nominal capacities predicted from American, Australian and European codes, including 390 numerical data obtained in this investigation. The safety levels of design rules given in these standards were examined by performing a reliability analysis. It has been demonstrated that the current design rules given in the American, Australian and European codes provide conservative predictions. A modified design method based on the recommendations given in European code was proposed in this study. Overall, it has been proved that the proposed design rule provides accurate and reliable predictions for the design of cold-formed S700, S900 and S1100 steel grades SHS and RHS beam–columns.

Comparative study on seismic performance of concrete-filled double skin tubular piers and hollow concrete piers: Experimental and analytical

Hollow bridge piers with concrete-filled double skin tubular (CFDST) section could offer more efficient fabrication and better confinement effect, but increase construction cost with the use of steel tubes if compared to regular hollow concrete bridge piers. Although hollow concrete piers and CFDST piers have been the focus of the existing experimental and numerical studies, there is limited information available regarding to the seismic performance comparisons of the two systems while considering the cost perspective. Therefore, a comparative study was carried out in the current study to compare the seismic performance of the two designs quantitatively, while considering the cost effectiveness. The experimental results of the two designs were compared in terms of lateral force bearing capacity, deformation capacity, energy dissipation, stiffness degradation, residual displacement, and performance per cost ratio. It has been found that the lateral force bearing capacity, the displacement ductility, the effective pier flexural stiffness and the performance per cost ratio of CFDST pier increased by 50.2%, 16.7%, 22.9% and 36.5%, respectively, while the residual drift ratio reduced by 33.3% at a large drift ratio of 3.0%. In addition, the seismic performance of another two CFDST piers with different diameter-to-thickness ratio of outer steel tubes and hollow ratio was studied through cyclic lateral loading tests. A verified finite element model was also developed to further conduct parametric study to fully investigate the influence of the diameter-to-thickness ratio of outer steel tubes and hollow ratio on the seismic performance of CFDST piers. Experimental and numerical results have found that the diameter-to-thickness ratio of outer steel tubes is one of the most important factors that influences the seismic performance of CFDST piers. In contrast, the hollow ratio significantly influences the deformation capacity of CFDST piers without significantly affecting the lateral force bearing capacity. The diameter-to-thickness ratio of outer steel tubes is suggested to take between 60 and 150, and the hollow ratio is suggested to take between 0.5 and 0.7 for cost effectiveness and ductile seismic design purposes of CFDST bridge piers.

Study on Mechanical Behavior of Fully Encased Composite Slender Columns with High-Strength Concrete Using FEM Simulation

The most common types of composite columns used in high-rise structures are concrete-filled steel tubes (CFSTs) and concrete-encased steel (CES) that are either entirely or partially encased in concrete. The attempt of this study is to develop a suitable constitutive model addressing the behavior of fully encased composite slender columns with high-strength concrete subjected to axial loading. The nonlinear finite element (FE) package ABAQUS version 6.14-2 is used to study the response of fully encased composite (FEC) slender columns. The finite element analysis (FEA) results are validated with experimental data extracted from previous experiments. Then, the parametric study is conducted on rectangular FEC columns with different shapes of encased steel encasements to investigate the axial load-carrying capacities, axial deformation, ductility, load-deformation behavior, and confinement of FEC columns. The governing parameters for the current study are the high strength of concrete (90 MPa, 100 MPa, and 120 MPa), shapes of encased steel sections (circular, I-shaped, and rectangular steel encasements), and spacing of tie bars (50 mm, 100 mm and 150 mm). 6–21% of load increment is observed by changing the concrete compressive strength. A comparison is also made between the results of reinforced concrete and FEC slender columns and 2–11% of load increment is recorded by changing the shape of structural steel and keeping other parameters constant. The results of calibrated finite element models revealed that closely spaced tie bars resulted in a good ductility of FEC column with high-strength concrete (HSC). Significant enhancements in the axial load capacity are observed in the case of FEC slender columns than in RC slender columns of the same size and shape. Ductility and residual strength after the failure of FEC columns are also observed to increase significantly with the adoption of tubular structural steel sections. However, increasing the concrete strength results in the reduction of this ductility.

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.

Cold-formed steel elliptical hollow section stub columns under combined compression and biaxial bending

The paper presents a numerical study on the cross-section behavior of cold-formed (CF) steel elliptical hollow sections (EHS) under combined compression and biaxial bending. In the present study, a finite element (FE) model for CF steel tubular stub columns under combined compression and biaxial bending was first developed, in which the local geometric imperfections, residual stresses and enhanced material behavior were predicted by a rigorous numerical simulation of roll forming. The developed FE model for CF steel tubular stub columns under combined compression and biaxial bending was validated against test results of various tubular sections (including EHS). Then, the validated FE model was employed to carry out a parametric study for CF steel EHS with a large range of steel grades (including both high strength and normal grade steels), section sizes, loading eccentricities and angles. Based on the generated FE data, the traditional design specifications for doubly symmetric cross-sections under combined loading in EN 1993-1-1: 2005 (CEN, 2005) and ANSI/AISC 360-16 (AISC, 2016), as well as the current design equations for hot-finished (HF) normal grade steel EHS suggested by Gardner et al. (2011) under combined loading were evaluated for the design of CF steel EHS under combined loading. New slenderness limits of Class 2 and Class 3 sections, as well as new design equations of cross-section resistances, for CF steel EHS stub columns under combined compression and biaxial bending are proposed.

Bufalin alleviates acute kidney injury by regulating NLRP3 inflammasome-mediated pyroptosis.

Recently, there has been an increasing clinical incidence of acute kidney injury (AKI), which rapidly declines renal function and leads to massive tubular cell necrosis. Pyroptosis is an inflammatory process of cell death that is more rapid than apoptosis, which is accompanied by a massive release of inflammasome activation. In the study, we aim to explore whether Bufalin regulates the AKI through the pyroptosis pathway. We have established gentamicin (GM)-induced AKI animal and cell models to simulate the pathological conditions of kidney injury. The expression of renal injury and pyroptosis-related indicators were detected by western blot. PAS staining and IHC staining were used to analyze renal function. CCK-8 assay was performed to detect cell viability after AKI with different treatments. TUNEL staining, flow cytometry and immunofluorescence assays were performed to measure pyroptosis. After intraperitoneal injection of GM in rats, renal function was significantly decreased, along with a significant increase of damaged and necrotic cells as suggested by renal tubular epithelial tissue sections. In addition, there was an increase in the pyroptosis-related markers expression and pyroptosis-induced cell death. Consistently, studies in vitro found that GM significantly induced pyroptosis and its associated protein expression in NRK52e cells. Whereas, the administration of Bufalin reversed these effects of GM in vivo and in vitro. Further, we found that Nigericin (NLRP3 agonist) could reversed the effects of bufalin on GM-induced pyroptosis. Bufalin attenuates pyroptosis generated AKI by inhibiting NLRP3 inflammasome.

Experimental investigation on the structural behaviour of novel non-metallic pultruded circular tubular GFRP T-joints under axial compression

Different uniplanar T-joints made from pultruded glass-fibre reinforced polymer (GFRP) circular tubular sections (CHS) incorporating different innovative non-corrosive reinforcements with structural adhesives, carbon-fibre laminates (CFRP) and concrete-filled GFRP rods were developed, and their structural performance was tested under axial compression. The hollow T-joints without any connection reinforcements displayed brittle failure with out of plane longitudinal shear failure while the ones reinforced with CFRP and concrete-filled GFRP rods shows superior ultimate strength and ductility with diverse failure modes including interlaminar failure within the pultruded chord. With CFRP wrapping and concrete filling, increases in strength and ductility of up to eightfold and fortyfold were seen, respectively. Design oriented equations and analytical formulations were developed for the T-joints and their predictions were compared with experimental results. These novel connections presented in this study are recommended for future construction of offshore tubular structures.

Design and Comparative Analysis of Pratt Roof Trusses Using Angular and Tubular Steel Sections through Limit State Method

A Pratt truss is a type of truss structure which is used in civil engineering to support heavy loads. It is comprised by the diagonal members and vertical members, which transmits the loads efficiently through a combination of tension and compression which is easy to construction and suitable for both short and medium span. But this project work is made to decide to structural performance employing angular and tubular steel sections by using Limit State Method by considering the economy and strength having 30 m span and rise height 5 m, with the help of software we analyse the truss by using angular and tubular sections. The analysis is carried out through STAAD Pro software and two steel sections were made to find their weight of steel, deflection which decides which structure is more economical to use. The outcomes of this project is that consists of comparative study on Pratt roof truss using angular and tubular steel sections by Limit State Method with help of STAAD Pro software to determine the optimistic, adequate and economic structure, then the loads are applied according to the Is 875 code, assigning steel sections such as channel, I-sections, etc. By the study of project we got the tubular section is economical to use as compared to angular section. Keywords: Structural Analysis, Roof Truss, STAAD PRO, Pratt truss, Limit State Method (IS 800:2007, IS 875-1975 (Part I, II & III)

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.

A Slenderness-Based Method for Web Crippling Design of Aluminum Tubular Sections

A Slenderness-Based Method for Web Crippling Design of Aluminum Tubular Sections

A Slenderness-Based Method for Web Crippling Design of Aluminum Tubular Sections

A Slenderness-Based Method for Web Crippling Design of Aluminum Tubular Sections

Submerged Friction Stir Back Extrusion of AZ31 Magnesium Alloy

Friction Stir Back Extrusion (FSBE) is a new grade of severe plastic deformation process capable of producing metallic tubular geometries that exhibit ultrafine grain structure and superior mechanical properties. FSBE of tubular sections provide opportunities for producing lightweight rigid structures for the automotive, aerospace and construction industries. This research investigates the effect of submerging conditions (in water at 25 °C and 2 °C) for Magnesium AZ31-B tubes on the grain size, mechanical properties, temperature history and power consumption. Submerged FSBE is compared to FSBE in air at fixed process parameters of 90 mm/min and 2000 rpm. It is shown that the impact of submerging is statistically insignificant in terms of the mechanical properties, ultimate tensile strength and percent elongation, of the produced tubes according to the conducted t-tests. On the other hand, the optical microscopy results indicated finer grains at the inner wall of the seamless tubes for FSBE in air and underwater FSBE at 25 °C when compared to underwater FSBE at 2 °C.

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.

Experiments on cyclic behaviour of cold-formed steel-rubberised concrete semi-rigid moment-resisting connections

This paper presents the results of full-scale physical tests on a recently developed cold-formed steel (CFS) semi-rigid moment-resisting connection infilled with rubberised concrete (RuC) for seismic application. The connection comprises side-plates attached to both sides of built-up tubular CFS beam and column sections through either screwed or welded connections. The tests were performed on both bare steel and CFS-RuC composite connections under cyclic loading for comparison purposes. The predominant modes of failure are beam local buckling and side plate plasticity in the bare steel connections and screw shear failure in the composite connections. The results show that the composite connection typically reaches 45% higher strength and 21% greater energy dissipation capacity than the bare steel connection both having 24 screw arrays. These indicate the beneficial effects of the infill RuC in prevention of the beam local buckling in connections with identical connection configuration. The energy dissipation capacity of the bare steel connection having 36 screw arrays, however, was 70% greater than that of the composite connection with 24 screw arrays. This reflects side plate plasticity being a more effective energy dissipation mechanism than the other identified mechanisms.

Void Fraction Measurement and Prediction of Two-Phase Boiling Flows in a Tubular Test Section

Abstract Void fraction is one of the most important parameters that affect two-phase flow heat transfer and pressure drop. In this paper, a commercial gamma densitometer and a high-speed X-ray radiography system developed at the University of Michigan (UM) are used to measure the void fraction in two-phase boiling flows, with water as the working fluid, in a tubular test section. The test section is made of Incoloy 800H/HT with a total length of 1.589 m, an inner diameter of 12.95 mm, and a wall thickness of 3.05 mm. These two instrumentation systems are installed on a traversing platform that travels along the vertical test section to perform measurements at multiple elevations. Subcooled flow boiling and natural convection boiling experiments are performed to measure the void fraction in the test section. Flow visualization images are obtained for bubbly and slug flows from the X-ray radiography system. The wall temperature of the test section is measured at 17 elevations by thermocouples. In addition to the experiments, a multiphase computational fluid dynamics (MCFD) model is developed using ansysfluent to simulate the subcooled flow boiling. The measured wall temperature and void fraction from the experiments are compared with the MCFD simulation results. The root-mean-square (RMS) relative deviations are 3.6% and 16.1% for the wall temperature and void fraction, respectively, between the experimental data and MCFD simulations.

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.

Design Buckling Resistance of High Strength Steel Members

AbstractEN 1993‐1‐1 gives stability design rules for columns, beams and beam‐columns up to S460, whereas EN 1993‐1‐12 gives additional guidance for S500 up to S700 (based mainly on numerical work available at the time). Recent studies on flexural buckling of welded H, I and box columns in steel grades S460 to S960, even though limited, show that improved curves can be used for members in high strength steel (HSS). The research project RUOSTE also reported improved buckling curves for HSS box and tubular sections compared to those in Table 6.2 of EN 1993‐1‐1. This improved behaviour is usually attributed due to the improved material properties but mainly due to the more favourable residual stress distribution.Recently, within the European Project STROBE evaluation of the European stability design rules was carried out covering columns, beams, and beam‐columns. The research was based on experimental programme covering 20 full‐scale tests, residual stress measurements, advanced numerical models, analytical derivations, and statistical evaluation. Finally, it was possible to provide new, more relaxed recommendations for the buckling curve selection for HSS members.This paper provides a summary of the project conclusions regarding the stability design of steel members in high strength steel, where firstly a brief overview of the experimental results is presented, followed by the numerical parametric study, results evaluation, and discussion.

Impact of fiber reinforced polymer composites on structural joints of tubular sections: A review

Tubular structures are the base of rational design with the improvement in high-performance and advanced structural applications. One of the biggest challenges of these parts is their complex/superior architectural geometry, therefore, knowledge is required to understand the features of each joint. In recent times, conventional metal tubular joints are replacing with fiber reinforced polymer (FRP) tubular joints in various applications, such as aerospace, automotive, civil construction, etc. This is due to lightweight and excellent corrosion resistance of FRP tubular joints compared to conventional metal tubular joints. In this review, the use of different types of tubular joints (T, L, X, and K-joints) and their failure mechanisms are discussed in detail. Further, the role of FRP composites in joining the tubular sections and reducing their weight is discussed. In addition, some specific failure modes (chord shear failure, local buckling, brace failure, etc.) for various types of tubular joints are given in detail. At the end of this review, several practical applications based on the classifications of tubular joint structures are reviewed. This review may provide several ideas and new directions to researchers for extending their skills in the field of composites to design innovative structural members in aerospace and automotive fields and architectural buildings, etc.

Cold-formed ferritic stainless steel SHS and RHS beams: Testing, modeling and design

Ferritic stainless steel is characterized by its low or even no nickel content and has relatively lower material cost than austenitic and duplex stainless steel. It may offer a viable alternative in structural applications. In this study, a series of four-point bending tests was firstly carried out on cold-formed ferritic stainless steel (CFFSS) square and rectangular hollow sections (SHS and RHS) to investigate the flexural performance of the tubular section beams. A finite element model was then developed for CFFSS tubular beams. The model was shown capable of predicting the flexural behavior of the beams and therefore an extensive parametric study was undertaken to generate more data over larger ranges of key parameters of the CFFSS sections. The experimental and numerical results as well as the available data on CFFSS SHS and RHS beams were employed to assess the slenderness limits as well as to evaluate the moment capacities predicted by various design provisions such as the American Specification, Australian/New Zealand Standard, European Code, direct strength method and continuous strength method for cold-formed stainless steel beams. It is shown that the current design methods provided quite conservative predictions on the moment capacities of the CFFSS flexural members. Reliability analyses were undertaken and appropriate design rules for CFFSS SHS and RHS beams were suggested in this study.