Stainless Steel Beam Research Articles

3D printing of flexible piezoelectric composite with integrated sensing and actuation applications

3D printing of flexible piezoelectric composites (3D-FPCs) is increasingly attracting the attention due to its unique advantage for customized smart applications. However, current research mainly focuses on the 0–3 piezoelectric composites, in which the piezoelectric ceramics are embedded in polymer matrix in the form of particles. The poor connectivity between particles much reduces the conduction of strain and charge in the composites, seriously limiting its application in actuation. In this work, a continuous lead zirconate titanate (PZT) double-layer ceramic scaffold was prepared by 3D printing and assembled with epoxy resin and interdigital electrodes together to manufacture a multifunctional device. The 3D-FPCs exhibit a free strain of 1830 ​ppm in actuating and are able to actuate a stainless-steel cantilever beam to produce a tip displacement of 5.71 ​mm. Additionally, the devices exhibit a sensitivity of 26.81V/g in sensing applications. Furthermore, 3D-FPCs are demonstrated as actuators for mobile small robots and wearable sensors for sensing joint activities.

Flexural behaviours of concrete-filled stainless-steel tubular beams under cold-region low temperatures

Applications of concrete-filled square (or circular) stainless-steel tubes keep increasing in cold-region coastal engineering structures. However, their behaviours under low-temperature bending have not been fully investigated, which brings obstacles to their engineering applications. To address this issue, this paper investigated flexural behaviours of concrete-filled square/circular stainless-steel tubular beams (CFSSSTBs/CFCSSTBs) at low temperatures through eight four-point bending tests. The main studied parameters were low temperatures (20∼−60 ℃) and cross-section type (circular or square shape). Test results showed that both CFSSSTBs and CFCSSTBs exhibited flexural failure and exhibited excellent ductility under low-temperature bending benefiting from the excellent ductility of stainless steel; bending resistances of CFSSSTBs and CFCSSTBs were improved by 5% and 22%, respectively. This study also developed finite element models (FEMs) for simulations on flexural behaviours of CFSSSTBs/CFCSSTBs at low temperatures. The FEMs considered both low-temperature material and geometric nonlinearities. Validations against eight tests proved the capacities of FEM simulations on low-temperature flexural behaviours of CFSSSTBs/CFCSSTBs. Finally, the code equations in Eurocode 4 and AISC 360 were used to predict the stiffness and ultimate bending resistances of CFSSSTBs/CFCSSTBs. Validations showed that the code equations underestimated the bending resistances of CFSSSTBs/CFCSSTBs. This study provided fundamental information on the flexural bending mechanism of CFSSSTBs/CFCSSTBs) at low temperatures.

Classification and ultimate capacity of duplex stainless steel H-section under cyclic loading

Stainless steel materials are high ductility and strain hardening under cyclic loading, which is promising in seismic design. However, the current European stainless steel structure design code prEN 1993-1-4(EC3) ignores this favorable effect in the cross-section classification, as well as the lack of prediction formulas for the ultimate capacity of H-section under cyclic loading. In this paper, parametric analysis was carried out for H-section to extend the database based on the existing test results after calibration of the finite element model. The cross-section classification criteria of duplex stainless steel beams and beam-columns around major-axis under cyclic loading were investigated, and the EC3 classification of stainless steel H-section was evaluated. The predicted results for EC3 are conservative due to not considering the constraints of the cross-section component plates and the favorable conditions for the material strengthening of stainless steel under cyclic loading. Based on this, classification criteria for stainless steel H-section under cyclic loading were proposed and summarized. Subsequently, the method of calculating the ultimate capacity methods under cyclic loading suggested by EC3, Chen and Zhou et al. were evaluated. The results show that EC3 is on the conservative side, with actual results being generally 1.5 times higher than the predictions. In contrast, Chen and Zhou et al.'s method is on the unsafe side of the prediction. Finally, improvement suggestions are given for EC3 and the continuous strength method by considering the over-strength factor under cyclic loading, respectively, with results exhibiting high accuracy.

Failure analysis of an AISI 310 stainless steel beam reinforcement fracture during service in a rolling beam furnace

This work investigated the premature failure of a beam reinforcement made of austenitic stainless steel AISI 310 used in the entrance of a rolling beam furnace working continuously at cycles from 650 to 850 °C. Fracture surface and microstructural investigations allowed to identify the fracture mechanism as fatigue failure. The fracture was probably initiated at the oxidized grain boundaries at an early stage of service life, when no microstructure degradation was present, while most of the fatigue crack propagation occurred after the precipitation of secondary phases. The microstructure investigation revealed severe microstructure degradation with the presence of intermetallic sigma (σ) phase (area fraction = 19 %) and M23C6 carbides (area fraction = 1 %), which were formed during the high-temperature exposure. Cracking of σ phases and decohesion at σ /austenite matrix interfaces were observed near the fracture and in the small punch test samples. Such discontinuities provide an easy path for crack propagation.

Flexural Strength of RHS Perforated Lean Duplex Stainless Steel Beam at Temperature 24-900ºC

The investigation of stainless steel structures at elevated temperatures is still limited, especially to those focused on the behaviour of perforated beams. Therefore, a numerical study was conducted to investigate the behaviour and strength of cold-formed lean duplex stainless steel (CFLDSS) beams having a single web perforation that failed due to pure bending at temperatures between 24-900oC. In total, 200 square and rectangular hollow sections (RHSs), which had various cross-section sizes, hole diameters, and temperature simulations, were involved in the parametric study. The numerical study was based on the ABAQUS simulation results of the 200 specimens. The numerical model was developed based on the validated existing studies. Numerical evaluations show that the existing codified strength predictions are conservative, but it has inconsistent safety. Hence, this study suggests modifications to the existing strength prediction, which is more conservative and reliable.

Experimental investigation of global-distortional interaction buckling of stainless steel C-beams

This work reports the test data for press-braked stainless steel C-beams subjected to global-distortional (G-D) interaction. The chemical constituents of austenitic S30408 used in the tests were proved to meet the European (EN 10088–1:2014) and Chinese (GB/T 3280–2015) codes. The tensile test of the material was performed to determine the mechanical properties of the flat and corner areas of the press-braked C-beams. Initial imperfections of each specimen were assessed before conducting the bearing capacity tests. A total of 10 specimens consisting of 20C-beams were subjected to four-point bending. All specimens first underwent distortional buckling and then global buckling. The vertical displacement at the mid-span and the loading points, support rotation, distortional deformation, lateral deformation, strain at the boundary of the upper flange as well as strain of the lower flange were meticulously recorded and analyzed. Based on the observed test phenomena, the recorded displacement and strain data, the failure mechanism of G-D interaction and the development of the buckling waves were unveiled. The test data was employed to evaluate the accuracy of the design methods in accordance to the Direct Strength Method (DSM), EN 1993-1-4, AS/NZS 4673 and ASCE 8–22. All codes are found to account for distortional buckling by employing the Effective Width Method (EWM) to reduce the compression plate area. The evaluation results revealed that DSM could safely and stably make a prediction of the ultimate capacity for G-D interaction in stainless steel beams, while EWM have a lower performance in prediction.

Corrosion Testing of Laser Welded Austenitic Stainless Steel Welds

Laser welding is becoming increasingly common in industrial applications for welding stainless steels. To reduce costs, hot-rolled stainless steel beams can be replaced by laser-welded structures. In our research, the corrosion resistance of laser-welded T-joints made of 1.4301/304 austenitic stainless steel were investigated. The joints were welded one or both sides, with different combinations of travel speed and laser power. Electrochemical corrosion measurements were performed in 3.5% NaCl solution in a standard three-electrode corrosion cell.

Bending resistance of austenitic stainless steel hollow sections at elevated temperatures

The present research aims to increase the knowledge of the structural behaviour of stainless steel members under fire. Eight experimental bending tests at elevated temperatures (500, 700 ºC) built with RHS 150×100×3 austenitic stainless-steel beams, using two different grades (1.4301, 1.4571) also known as 304 and 316Ti, are presented. Both grades 1.4301 (X5CrNi18–10) and 1.4571 (X6CrNiMo17–12–2) have almost the same core chemical composition but there are some differences, especially the grade 1.4571 has 2–2.5% molybdenum and a small amount of titanium (less than 0.7%). Grade 1.4301 presents good rust resistance, sufficient acid resistance and good weldability, while grade 1.4571 presents very good rust resistance, very good acid resistance and also good weldability. Both have almost the same strength, but grade 1.4571 has superior strength at elevated temperatures. Both material grades were experimentally characterised with coupon tensile tests at room temperature. The load-displacement behaviour is validated with 3D shell finite element models, assuming a true stress-strain material model, based on the two-stage Ramberg Osgood constitutive law. With the developed numerical model, a parametric analysis is presented to study the fire resistance of beams from both materials, using three different cross-sections and eleven different temperatures. The bending resistance obtained with the finite element model is in good agreement with the cross-sectional design moment resistance, when considering the effective area, confirming that the design rules from EN1993–1–2 are safe for less slender cross-sections and unsafe for the most slender cross-sections.

Cold-formed stainless steel beams with single web hole at elevated temperatures

Steel structures are often used in buildings due to their advantage in weight-to-strength ratio. However, their structural capacity deteriorates in fire as the temperature of the structures rises. Investigation of cold-formed stainless steel (CFSS) structures at elevated temperatures is still limited, especially for rectangular hollow section (RHS) beams having a single web hole in the mid-span (perforated web). Therefore, a numerical investigation was conducted to evaluate the current design provisions to calculate the strength of such beams at elevated temperatures ranging from 22 - 900 °C. A total of 400 specimens of stainless steel grades austenitic (EN 1.4301) and lean duplex (EN 1.4162) were considered. The investigation used finite element analysis (FEA) to simulate the behaviour of RHS beams with perforated web under pure bending. The finite element (FE) model was validated against a series of experimental results available in literature. The comparison between flexural strengths obtained from FEA with design values calculated from the current design rules showed that the design rules are conservative. However, they are not always reliable and safe for RHS beams without and with a perforated web for the two material grades at elevated temperatures. In this study, only the design rules specified by Eurocode 3 are shown to be reliable and safe.

Calibration of ductile and shear damage models for carbon and stainless steel shear studs

AbstractSteel‐concrete composite beams are commonly used in bridge construction. The corrosion of the supporting steel beams and the shear connectors are however known as a major cause of premature deterioration of composite bridges. Stainless steel beams and shear connectors offer a viable alternative solution to the steel corrosion problem in composite bridges located in harsh environmental conditions. This paper presents experimental and numerical investigations of the tensile and shear behaviour of stainless steel welded shear connectors. The results of tensile coupon and double shear tests on stainless steel and carbon steel shear connectors to characterise the tensile and shear response are reported. Numerical modelling is carried out using the ABAQUS finite element software to develop calibrated ductile damage and shear damage fracture models for stainless steel shear connectors. The development and validation of the numerical models together with the calibration of the fracture models are presented and comparisons are made with those of carbon steel shear connectors.

Imperfection Sensitivity of Plastic Shear Buckling Behavior in Corrugated Web Stainless Steel beams

AbstractThe shear behavior of corrugated web beams can be highly sensitive to the presence of initial imperfections. The designer has, in general, no prior information about the mechanical and geometric imperfections of welded elements. As a solution, in a FEM‐based design, the eigen buckling deformations with an equivalent maximum magnitude are included as an equivalent initial imperfection in a nonlinear analysis to account for the simultaneous effects of geometric imperfections and residual stresses. Previous researchers investigated the effects of initial imperfections in the form of different eigenmodes found via linear buckling analysis. They concluded that the shear strength rises with mode number, with the first mode providing the most crucial condition. However, it is shown in this paper that such a methodology is not applicable to stainless steel corrugated web beams in the medium slenderness ratio range when shear yielding precedes shear buckling. It is observed that, unlike in elastic buckling, in plastic buckling the first buckling mode does not result in the minimum strength. The results show that in FEM‐based design, using the first mode instead of the critical mode as the shape of the initial imperfection can result in a maximum of 19% and 31% overestimation of the ultimate shear capacity for the imperfection amplitudes of tw and hw/200, respectively.

A strain rate-dependent analytical approach for low-velocity impact on the beam composed of silicon-nitride and stainless-steel

Purpose The purpose of this study is to investigate the strain rate effect on the problem of low-velocity impact (LVI) on a beam, including silicon nitride and stainless steel materials. Design/methodology/approach Based on the nonlinear Hertz impact mechanism, the energies related to the impactor and the beam are written, and motion equations are derived using the Lagrangian mechanics and Ritz method. The strain rate term is represented as a damping matrix in the equations of motion. In the issue of LVI on the silicon nitride and stainless steel beam, the effect of internal viscous damping coefficient in simply–simply and clamped–free boundary conditions are studied. Also, the influence of the volume fraction index in the range between zero and one and greater than one on the impact response is investigated. Findings The results make it clear that the strain rate parameter had little effect on the response in LVI. Also, an increase in the volume fraction index has led to a decrease in the contact force and an increase in the rebound velocity of the impactor. Originality/value The effect of strain rate on LVI is theoretically studied in this paper, while in most of the papers, this effect is investigated experimentally and numerically.

Fire resistance of austenitic stainless steel beams with rectangular hollow sections

AbstractThis paper presents a study on the structural behaviour of stainless steel profiles under fire conditions. An experimental campaign of three‐point bending tests on rectangular hollow section beams of the grade 1.4301 (also known as 304) were conducted, considering both steady‐state and transient state conditions. Prior to those tests, the mechanical characterization of the stainless steel was investigated. The constitutive laws obtained by tensile tests at high temperatures are compared with those recommended in Eurocode 3, whose respective material models were recently proposed for modifications, still requiring complete validation. In addition, numerical modelling of the bending tests has been performed afterwards achieving close approximation to the observed experimental results. Finally, analytical methods to predict the load‐deflection behaviour are also presented. Good agreement between the considered methodologies was attained validating their application on the prediction of the fire behaviour of stainless steel beams.

Testing, FE modelling and design of pin-ended stainless steel equal-leg angle section columns and beam–columns

The behaviour and design of pin-ended stainless steel equal-leg angle section members under compression and compression plus minor-axis bending are investigated herein. The studied members are cylindrically pinned about the minor axis. An experimental investigation, including material testing, initial geometric imperfection measurements and physical tests on hot-rolled stainless steel equal-leg angle section members is first presented. Numerical models are developed and validated against the new experimental data. A numerical parametric study is then presented considering both hot-rolled and cold-formed stainless steel angle section columns alongside beam–columns with a wide range of slenderness values. Finally, new design proposals for pin-ended stainless steel equal-leg angle section members under compression and combined compression and minor-axis bending are developed and verified against the results of existing physical experiments, as well as the newly-generated test and numerical results. The proposed design rules are shown to offer substantially more accurate and consistent resistance predictions compared to existing codified design rules. The reliability of the new design provisions, with a recommended partial safety factor γM1=1.1, is verified following the EN 1990 procedure.

An interaction formula proposed for stainless steel SHS and RHS beam–columns

This paper is focused on stainless steel square and rectangular hollow section (SHS and RHS) slender members loaded by a combination of compressive force and the bending moment. The study presents tests on 20 members, including initial imperfection measurements and material coupon tests. The tests take into consideration uniaxial bending to the major axis. The data obtained from the experimental study were subsequently used for validating an FE numerical model. A comprehensive numerical parametric study was carried out on all three common structural stainless steel groups: austenitic, ferritic and duplex. The cross-section slenderness and the cross-section aspect ratio (h/b), the non-dimensional member slenderness, the material stress–strain diagram (yield strength, ultimate strength, degree of non-linearity) and the ratio between the compressive force and the bending moment were set as the main parameters. Results of the numerical parametric study were compared with some of the existing procedures for stainless steel beam–column design. The main focus is on the proposal developed by Zhao et al., which is the procedure expected to be used in the new EN 1993-1-4. Although the method published by Zhao et al. has shown good prediction ability, a new design approach was proposed and its suitability demonstrated by a reliability study. The method is believed to be more general, as it uses a single formula for all grades of stainless steel, and also covers the effect of the section Class on the interaction between axial force and bending moment.

Behavior of Stainless-Steel Hot-Rolled Channel Section Beam–Columns: Testing, Modeling, and Design

This paper presents a testing and numerical modeling program on the global stability and resistance of stainless steel hot-rolled channel section beam–columns under combined compression and minor-axis bending. The testing program comprised material tests, imperfection measurements, and 18 beam–column tests. Following the testing program, systematic numerical simulations were conducted; finite-element models were developed to simulate the test observations and conduct parametric studies to obtain more numerical data. The obtained experimental and numerical results were analyzed and used to perform a design analysis, in which the accuracy of interaction curves prescribed in the US and European design codes for stainless steel hot-rolled channel section beam–columns was assessed comprehensively. The results of the design analysis generally revealed that both the US and European interaction curves yield unduly inaccurate and scattered resistance predictions due to the use of inappropriate curve shape and inaccurate end points. A new design interaction formula is proposed using a more appropriate curve shape and more-accurate end points. The new interaction curve was shown to be capable of offering greatly improved design accuracy and consistency compared with the US and European curves.

Experimental study of local – Distortional interaction of press-braked stainless steel lipped channel beams

Stainless steel lipped channel beams are prone to complex buckling modes due to the large width-thickness ratio. An in-depth experimental study of local – distortional interaction of press-braked stainless steel lipped channel beams was conducted. The chemical composition was proved to meet the requirements of European and Chinese standards. A tensile test of four coupons extracted from the press-braked lipped channel beams was carried out to investigate the material properties. A total of 10 specimens composed of 20 press-braked stainless steel lipped channel beams were investigated in the bearing capacity test. The relationship of the vertical displacement of mid-span, vertical displacement of loading points, support rotation, flange deformation and web deformation with the load was obtained, as well as the bearing capacity of each specimen. According to the measured displacement and strain, the development and failure mechanism of local – distortional interaction of stainless steel lipped channel beams were revealed. All test specimens were subjected to local buckling first, then distortional buckling, and finally interaction buckling. Each specimen had a certain post buckling strength. Near the failure load, each specimen experienced a long loading process and showed good ductility. The test results were utilized to assess the existing design methods which were all based on Direct Strength Method for the guidance of engineers. The existing design methods for local – distortional interaction underestimated the bearing capacity of press-braked stainless steel lipped channel beams. The existing design methods for local buckling or distortional buckling of stainless steel beams overestimated the bearing capacity of local – distortional interaction.

Local – distortional interaction buckling of stainless steel lipped C-section beams

Based on a bearing capacity test of 10 specimens composed of 20 stainless steel lipped C-section components, a refined finite element model was established and verified to investigate the failure mode and bearing capacity. 267 numerous parametric analyses were carried out to investigate the effects of the distribution and amplitude of initial geometric imperfections, strength improvement of corner and buckling slenderness ratio on the buckling modes and bearing capacity of stainless steel beams. The effects of both distribution and amplitude of initial geometric imperfections on the bearing capacity were significant. However, the effect of amplitude of initial geometric imperfections on the buckling modes was small. When the ratio of cross-sectional area of corner to the whole cross-sectional area was smaller than 5%, the increase of strength improvement of corner to the bearing capacity was within 5%. When the ratio was larger than 5%, the increase was more significant. The existing methods for calculating the bearing capacity of local – distortional interaction buckling of carbon steel and high-strength steel lipped C-section beams underestimate that of stainless steel lipped C-section beams. Therefore, two design methods for local – distortional interaction buckling of stainless steel lipped C-section beams based on Direct Strength Method were proposed for the first time. A reliability analysis of the proposed methods was conducted to verify the reliability for engineering application.

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.

Blended structural optimization for wire-and-arc additively manufactured beams

Current manufacturing techniques in the construction sector are slow, expensive and constrained in terms of architectural shapes. In other manufacturing sectors (such as automotive and aerospace) the use of automated construction systems significantly improved the safety, speed, quality and complexity of products. To realize real-scale structural elements for construction applications without ideally any geometrical constraints either in size or shape, the most suitable manufacturing solution for metallic elements is a directed energy deposition (DED) process referred to as wire-and-arc additive manufacturing (WAAM). The main advantage of WAAM relies on the possibility to create new shapes and forms following the breakthrough design tools for modern architecture as algorithm-aided design. At the same time, the printed part ensures high structural performances with reduced material use with respect to the conventional solution. The study presents a new approach called “blended” structural optimization, which blends topology optimization with basic principles of structural design and manufacturing constraints proper of WAAM technology, towards the realization of new efficient structural elements. The approach is applied to the case study of a I-type stainless steel beam on a multi-storey frame building. The approach could pave the way towards an efficient use of WAAM process to produce a new generation of structurally optimized elements for construction, with a more conscious use of the optimization tools and an efficient application of metal 3D printing.