Use Of High Strength Steels Research Articles

Numerical Study and Design Method for Lateral Torsional Buckling of High-Strength Steel Beams

Given the increasing use of high-strength steels in building constructions, the stability design of high-strength steel beams has become a crucial consideration. However, the current standards of various countries are based on analyses and fittings derived from conventional steel, rendering them unsuitable for high-strength steel. Moreover, existing research indicates that these standards underestimate the ultimate load-bearing capacity of high-strength steel beams. A finite element model was established to investigate lateral torsional buckling in high-strength steel beams. The obtained results were then compared with test results from experiments conducted on Q460GJ and Q690 steel beams. The reliability and accuracy of the established finite element model were validated. Through parametric studies, the impact of depth-to-width ratio, boundary condition, and steel grade on the stability coefficient was evaluated. It was observed that at the same non-dimensional slenderness, an increase in the depth-to-width ratio or a reduction in support constraints led to a decrease in the stability coefficient. It should be noted that the steel grade had little effect on the stability coefficient. Comparisons with the current steel structure design codes, such as EN1993-1-1, GB50017-2017, JGJ/T483-2020, and ANSI/AISC360-22 revealed an underestimation of the stability coefficient for clamped high-strength steel beams under uniformly distributed loads. Based on finite element simulations, stability coefficients for high-strength Q460, Q690, and Q960 clamped beams were determined. Similar to the stability coefficient proposed in GB50017-2017 for the lateral buckling stability design of steel beams, a lateral buckling stability coefficient for high-strength steel clamped beams subjected to uniformly distributed loads was proposed.

Corrosion behavior of austenitic stainless steel and nickel-based welded joints in underwater wet welding

Marine structures such as ports, bridges, pipelines, vessels, and platforms are an essential part of modern infrastructure, where the use of higher-strength steel provides savings in logistics and construction. However, the repair of higher-strength steels can be challenging, especially underwater. Wet shielded metal arc welding is the most widely used and least expensive method for underwater welding repairs, but is very susceptible to hydrogen-induced cracking. Thus, researchers and welding engineers aim to reduce the amount of hydrogen in the weld material. Recent success has been achieved through the use of austenitic welding consumables, such as austenitic stainless steel and nickel-based electrodes. The use of these consumables drastically reduces the amount of diffusible hydrogen in the weld metal. However, these austenitic materials usually have different corrosion potential as compared to the structural steel the weld beads are applied to. This creates the risk of severe galvanic corrosion. In the presented study, the corrosion behavior of welds created with austenitic stainless steel and nickel-based electrodes were studied. Samples were aged for 1.5 years in the Baltic Sea. Simultaneously, the effectiveness of corrosion protection systems such as coating and Impressed Current Cathodic Protection (ICCP) were evaluated. Localized corrosion occurred in the heat-affected zone when austenitic electrodes were used in the corrosive environment. The localized corrosion depth after 1.5 years in the Baltic Sea and in the salt spray layer was approximately 250 µm and 390 µm, respectively. The ICCP system and the use of a coating were effective in preventing localized corrosion. The low pitting corrosion density of 2.5 × 103 m−2 corresponds to grade A1 according to the standard and was found to be negligible as compared to the localized corrosion in the heat-affect zone.

Effect of annealing temperature on the evolution of microstructure, texture, and mechanical properties of hot-rolled 12Cr-ODS steel

To achieve high thermal efficiency, today's nuclear reactor structures are exposed to higher temperatures and pressures, which requires the use of high-strength steels with specific properties, such as ODS steels. There is a need to clarify the evolution of the microstructure and properties of steels at elevated temperatures. This study systematically investigates the evolution of microstructure, texture, and mechanical property variations of 12Cr-ODS steels after hot-rolling and subsequent annealing at 1000 °C and 1200 °C. The investigation utilizes optical microscopy, electron backscatter diffraction technique, and mechanical property measurements. The microstructure of hot-rolled samples shows a layered alternating distribution, which is distinguished by a notable presence of the α-fiber texture. Following annealing at 1000 °C, the martensite grains are smaller with a reduced hardness, while maintaining a strong α-fiber texture. After annealing at 1200 °C, there is a rapid increase in the growth of martensite grains, a significant rise in hardness, a reduction in the α-fiber texture characteristics, and an improvement in the γ-fiber texture characteristics. Moreover, the maximum intensity of the α-fiber texture diminishes as the annealing temperature increases. The mechanical properties of the samples deteriorated after annealing at 1200 °C, which can be attributed to the coarse martensite grains and the texture components containing the {001} cleavage plane dominating the occurrence of brittle cleavage fracture. The 0.1Y sample after annealing at 1000 °C exhibits an excellent combination of strength (1458 MPa) and ductility (20.3%), which is owing to the unique heterogeneous grain structure and the evolution of favorable texture.

Steel and composite bridges – Enabling sustainable solutions

AbstractSustainable bridges are characterised by three main aspects: saving resources by an efficient construction, allowing for a lifelong use of bridges by optimal detailing in view of fatigue and flexible design concepts for strengthening and adapting to changed user requirements. After a short introduction in the assessment of sustainability for bridges, an overview on recent bridge research in view of sustainability is given. The key point of efficient construction in future is the use of high strength steel (HSS): basic research and adaptation of rules are needed for welding of matching and mismatching connections. Joints and their relevant failure modes are to be investigated before hollow sections of HSS can be used in a wider range. And for steel and composite bridges, optimised plate buckling rules may serve for more efficiency in construction. Bridges are designed for a service life of 100 years. This can easily be achieved and even exceeded if the detailing is realised in view of fatigue. Research on welded details such as butt welds or joints of tubular bracings will be presented. Welds can be improved by post‐weld treatment such as high‐frequency mechanical impact (HFMI) treatment. Fatigue is also a key issue when steel and concrete or timber and concrete are combined for composite bridges. Reinforced composite slabs without prestressing require a fatigue verification for the transverse shear also in areas with cracked concrete. The notch forms an efficient connection in timber‐concrete composite (TCC) bridges, where, however, little has been known up to now on the fatigue behaviour.

Slab Reinforcement Contributions to Negative Moment Strength of Reinforced Concrete T-Beam with High Strength Steel at Exterior Beam-Column Joints

Previous studies have revealed that the contribution of slab reinforcement to the T-beam flexural strength in negative moment regions are not negligible for the seismic capacity design. An effective slab width (i.e., effective width of flanged section) has been proposed, within which the slab reinforcement needs to be included in the calculation of the beam nominal flexural strength in negative moment regions. These studies mainly focused on the cases using normal-strength steel in moment resisting frames. However, recently high-strength steel has been widely used in reinforced concrete moment resisting frames in high seismic regions to avoid congestion near beam-column joints. The use of high-strength steel may affect the beam stiffness due to the fact that it will require less amount of reinforcement, and result in a different normal stress distribution compared to the case with normal-strength steel. Therefore, this paper investigates the slab reinforcement contribution to the flexural strength of the reinforced concrete T-beam designed with high-strength steel in negative moment regions at exterior beam-column joints, for which nonlinear pushover analyses were conducted. Beam reinforcement grade was considered as a primary parameter with several other design variables including slab thickness, height, and span length of the beam. Analytical results show that the use of high-strength steel can result in a wider effective slab width than the case of normal-strength steel for calculating the beam nominal flexural strength under the negative moment. Based on these results, new design equations were proposed.

Buckling resistance of star-battened angle members made of high-strength steel

Recent upwards developments of the power grid requests lead to use of high strength steels (HSS) for the design and construction of higher and heavier loaded steel lattice transmission towers, or to strengthen the existing ones. Usually star-battened sections are preferred for the strengthening of individual members or in case of very high compression loads. Thus, the investigations focus here on the bearing capacity of a star-battened member made of two S460 L250x250x28 angles. The objective was to use a star-battened member made of two S460 L300x300x35 angles with a member length of 4486 mm that will be used in a specific project of 240 m high power transition tower. However, as the request in terms of length capacity cannot be met by the testing labs in Belgium, the studies have concentrated on the profile made of L250x250x28 angles.Firstly, a critical review of the current European normative documents (EN 50341, EN1993-1–3, prEN1993-3) has been made and the buckling resistance of the above-mentioned profile has been evaluated. Then, an experimental compression test has been performed for this member. The test has been complemented by a full non-linear finite element simulation by means of ANSYS software. Experimental, numerical and analytical results have been compared and discussed. Finally, conclusions were drawn considering the design of S460 star-battened members in compression. These studies are part of an ongoing project entitled “New steel” funded by Elia and ArcelorMittal and involving the University of Liège.

Exploring the Cable-Stayed Bridge with Shifting the Cable Arrangement at Deck Level

Cable stayed bridges are becoming a more and more viable option for lengthy spans with the development of computer-based optimisation techniques. Additionally, because they are suspended structures, they can be constructed with ease in locations where it would be challenging to provide several foundations or piers. The pre-tensioning forces of the cables on Sikkim's Akkar Bridge have been determined through this investigation. CSiBridge software is the programme utilised for the investigation. A analysis of the bridge's several parameters concludes this work. The parametric analysis looks at the deck moment, the bridge's span-wise reaction, the height of the pylon, and the length of the span in relation to the girder thickness. Also investigated is the impact of superstructure modifications on substructure. Due to a lack of resources, particularly steel, cable stayed bridges were initially created in Germany in the years following World War II. The effective introduction of cable stayed bridges is made feasible by the development of welding processes, advancements in structural analysis, the use of high strength steel, orthotropic type decking, and the previously noted shortage of steel in the years following World War II. Cable stayed bridges were extremely statically indeterminate structures. Electronic computers were essential in determining the precise solution to these extremely indeterminate systems and in analysing the cable stayed bridge. The software CSi Bridge is used to perform the analysis. Three distinct models of cable-stayed bridges have been constructed, each taking into account identical cable configurations under varying situations. Since the cables are arranged on the deck at various angles and attachment locations, their effects may be thoroughly investigated. IRC Class 70R Vehicle load was taken into consideration when taking live loads in accordance with IRC: 6-2017. Key Words: Cable-stayed Bridge, CSiBridge Software, IRC - 6, Analysis.

Design, Numerical and Experimental Testing of a Flexible Test Bench for High-Speed Impact Shear-Cutting with Linear Motors

Given the use of high-strength steels to achieve lightweight construction goals, conventional shear-cutting processes are reaching their limits. Therefore, so-called high-speed impact cutting (HSIC) is used to achieve the required cut surface qualities. A new machine concept consisting of linear motors and an impact mass is presented to investigate HSIC. It allows all relevant parameters to be flexibly adjusted and measured. The design and construction of the test bench, as well as the mechanism for coupling the impact mass, are described. To validate the theoretically determined process speeds, the cutting process was recorded with high-speed cameras, and HSIC with a mild deep-drawing steel sheet was performed. It was discovered that very good cutting edges could be produced, which showed a significantly lower hardening depth than slowly cut reference samples. In addition, HSIC was numerically modelled in LS-DYNA, and the calculated cutting edges were compared with the real ones. With the help of adaptive meshing, a very good agreement for the cutting edges could be achieved. The results show the great potential of using a linear motor in HSIC.

Experimental and numerical studies on UHPC-filled Q690 high-strength steel tubular members subjected to axial impact

With the advances in high-performance materials and structures, the impact behavior of ultra-high-performance concrete (UHPC) filled Q690 high-strength steel tubular columns was systematically investigated in this study. A total of 19 axial impact tests on UHPC-filled steel tubular columns were conducted by a drop hammer test apparatus, experimentally obtaining the failure model, impact force and displacement time histories, and energy absorption. The main parameters, including steel strength, steel ratio, impact energy, and specimen length, were considered. The results showed that UHPC-filled Q690 high-strength steel tubular members exhibited excellent impact resistance and could withstand higher energy impacts. As the impact energy increased, the impact force also increased owing to the strain-rate effect, and the deformation was significantly enlarged. Increasing the steel ratio significantly enhanced the impact resistance and energy absorption efficiency of components; the use of high-strength steel and UHPC also improved the impact resistance and energy absorption; the effect of specimen length on the axial impact behavior was limited. Additionally, a finite element model considering the strain-rate effects of high-strength steel and UHPC was established and benchmarked with the test results from the present study and literature. The simulated results were in good agreement with the experimental results, which contributed to the relevant research on UHPC-filled steel tubular components subjected to axial impact.

Economic and environmental assessment of high‐strength steel grades

AbstractEnvironmental impact awareness in civil engineering is nowadays an important concern. The last message from the IPCC (Intergovernmental Panel on Climate Change) was clear: significant actions are mandatory and urgent to achieve the objective to limit global warming to 1.5°C. The building sector is one of the most polluting industrial sectors for which economically viable solutions must be found to cut the emissions. The development of new production technologies can contribute to this aim by creating innovative and more sustainable materials. Amongst the new materials that appear on the steel market, high strength steels are a nice example as they offer higher strength to weight ratio of structural steel elements, resulting in material savings, lighter foundations, easier transportation, and erection. These multiple advantages explain why the use of high strength steels could lead to both significant carbon emission and cost savings. However, the production of such steels uses more alloying elements and sometimes they require more production energy than for regular grades. The aim of this paper is to estimate the relative prices and relative carbon emissions of high strength steels to evaluate whether they constitute sustainable materials. This paper demonstrates that, in many cases, the increase of relative prices and carbon emissions as function of yield strength can be negligible by contrast to the weight savings induced by using high strength steels.

Design optimisation of welded I‐beams made of high strength steels

AbstractNowadays, hot rolled steel sections are used in practice. The cross‐sectional dimensions are therefore fixed and catalogued by the steel manufacturers. However, when the span of the members and/or the applied load becomes significant, such hot rolled steel sections can no longer meet the ultimate and/or service design criteria and the use of a built‐up welded I‐beam should be considered. They are typically made of three steel plates welded together to form a monolithic I‐beam. By varying the dimensions of these plates, an infinite amount of cross‐section geometries can be defined. But face to this high variability of solutions, the designers encounter difficulties in identifying the most appropriate combination of geometrical and mechanical properties for the constitutive plates.To study and optimise these profiles, a MATLAB® routine has been developed at the University of Liege. It allows, for different load cases, to find suitable cross‐sectional dimensions that minimise the weight and/or the total cost of the element. This routine follows the current recommendations prescribed in prEN1993‐1‐5 and evaluates the possibility of using transverse stiffeners along the web to further reduce the weight and cost of the element. The so‐developed routine is presented in the present paper. Also, the advantage of considering the use of high strength steels for such structural members is discussed to propose recommendations to the designers for the selection of the most appropriate steel grade.

Review and outlook about the use of high strength steel in encased composite columns

AbstractThe trends of the modern construction are recognized for many years; go large span, go light structures, go sustainable, and keep it simple. In the holistic approach to construction a column remains one of the key structural elements.This article presents benefits of the application of high strength steel; namely the potential of using S500 and S550 for encased composite columns. The study shows the increase of the buckling capacity and reduction of weight and consequently reduction of the carbon footprint especially when applying XCarb® steel. The results are presented for a single member as well as for an internal column of a 156m high office building.It is assumed in the analyses that the simplified design method for composite columns defined in EN1994‐1‐1:2004 is applicable to higher steel grades and higher concrete compression classes. Different typologies of the encased steel cross sections are considered: simple H section in rectangular encasement, and cruciform section.

Influence of local features on twist springback of high-strength steel long channels

With the wide use of high-strength steel (HSS) in structural body parts, the twist springback of high-strength steel parts has received extensive attention. Unlike automotive panels, structural body parts are arranged with many local features to meet functional requirements. The aim of this study is to investigate the influence of local features on twist springback to optimize the design of local features to reduce twist springback. In this paper, a typical long channel part (A-pillar upper inner plate) is taken as the object of study. A suitable location division method for this type of part is proposed to investigate the changes in twist springback and cross-sectional stresses in the part before and after the addition of local features at different locations through finite element simulations. The results show that the local features affect the stiffness and stress distribution of the parts and significantly affect the twist springback of the parts. Finally, the research results guided the optimization of the local feature design of an A-pillar upper inner plate, resulting in a remarkable 37% and 61% decrease in twist springback at the left and right ends of the optimized part, respectively. In addition, stamping molds were developed for optimized parts, and experiments were carried out to verify the effectiveness of the law and the reliability of the finite element model.

Nonlinear Inelastic Stability Behavior of High-Strength Stainless Steel I-Beams with Sinusoidal Web Openings

Perforated beams can bring countless benefits compared to traditional plain-webbed beams. However, steel beams with sequential web openings are more susceptible to instabilities, and special care must be taken in a design concerning the failure modes these structures can present. The study presented herein explicitly dealt with the stability behavior of perforated beams with sinusoidal openings. This type of perforated member features smooth-lined openings constructed from a single thermal cut in conventional plain-webbed steel profiles. A broad study was carried out through numerical simulation using the ABAQUS software, in which perforated profiles manufactured with S600E high-strength stainless steel were studied. The use of high-strength steels in perforated profiles is a little explored topic in the literature, despite having a significant impact on the behavior of these elements. With the study carried out, a broad overview of the stability behavior of these members was obtained, especially concerning global stability. A total of 5940 FE models were developed, considering the application of different types of loads. In these models, linear buckling analysis (LBA) and geometrically and materially nonlinear analysis with imperfections (GMNIA) were performed. The results obtained were compared with international design codes, and it was found that some codes fail to represent the behavior of members that present lateral-distortional buckling (LDB) and interactions between local and global failure modes. This behavior is a significant design concern since the studied members had high yield strength, making them more susceptible to interaction-governed failure modes than usual-yield strength members. Additionally, the study found that some design codes do not accurately represent the behavior of members loaded outside the shear center due to the destabilizing effect of loading on these structures.

The optimum use of high-strength steel in the construction of gas transmission pipeline

PurposeThe aim of this study is to assess the opportunity for the development of hydrocarbon transportation using high-strength steel (HSS) in pipeline construction in terms of cost savings and reliability.Design/methodology/approachSeveral optimizations of pipeline design and operations were performed to estimate the total life-cycle cost variation associated with different grades of high-strength steel. The generalized reduced gradient (GRG) method was used in an Excel table to determine optimal total life cycle each pipeline. Variables used in this optimization with respect to each steel grade were as follows: pipeline external diameter, wall thickness, number of compression stations and installed power in each compression station. The reliability of a pipeline with optimal cost was assessed to highlight the impact of steel grade on pipeline reliability.FindingsThe study showed that the cost reduction is strongly dependent on the adopted gas pipeline configuration. The number of compression stations and external diameter are the main factors influencing the pipeline total life cycle cost, while the steel price seems to have a minor effect, the reduction of the gas pipeline total life cycle does not exceed 5% even with a 50% difference in pipe steel prices between X70 and X100 steels. On the other side, for the same external diameter, X100 steel presents better pipeline reliability against carbonic corrosion compared to X70 steel.Practical implicationsThe main contribution of this study is to provide a decision-support tool to help pipeline constructors enhance the profitability of natural gas transmission pipelines. The optimization method used is simple to use for design engineers during a feasibility study.Originality/valueThe present study presents one step to fill the gap concerning the question of balancing the trade-off between cost savings and structural reliability in high-strength steel pipelines during the early stages of feasibility studies. The optimal design and operations parameters ensuring cost savings on total life cycle costs are identified via an optimization method. The impact of selected optimal parameters on the long-term pipeline service life was estimated via a structural reliability analysis.

Prediction of transverse welding residual stress considering transverse and bending constraints in butt welding

Welding residual stress is generated by the thermal stress caused by rapid local heating and cooling during welding using a welding heat source. The distribution and size of the residual welding stress are affected by the joint type, welding conditions, constraints, etc., which also affect the fatigue, fracture, and buckling strengths. Therefore, because the magnitude and distribution of residual stress are very important for the safety evaluation of structures, guidelines for structural integrity evaluation suggest a method for deriving the welding residual stress. However, the welding residual stress presented in the guidelines is in a state without constraint; if a constraint exists, it is suggested to use the yield stress of the base material. This can lead to a very conservative design using the yield stress as the welding residual stress in the recent trend of the increasing use of high-strength steels with increased yield stress. Therefore, it is very important to investigate the relationship between constraint and residual stress during welding and to predict the residual stress according to the degree of constraint. In this study, the effects of member thickness, yield stress, lateral constraint, and bending constraint on the welding residual stress in butt welding were investigated, and predictive factors for welding residual stress were established. To this end, a thermal elastic–plastic analysis was performed by changing the thickness, yield strength, lateral constraint, and bending constraint size of the member. Subsequently, the analysis results were used to train a deep neural network (DNN) to predict the residual stress at the center of the weld and toe. In addition, the influence of input factors that affect the prediction accuracy during DNN learning was considered.

On Welding of High-Strength Steels Using Laser Beam Welding and Resistance Spot Weld Bonding with Emphasis on Seam Leak Tightness

The design of most electric vehicles provides for the positioning of the heavy energy storage units in the underbody of the cars. In addition to crash safety, the battery housing has to meet high requirements for gas tightness. In order to test the use of high-strength steels for this sub-assembly, this paper examines welded joints utilizing resistance spot weld bonding and laser remote welding, with special regard to the gas tightness of the welds. For this purpose, the pressure difference test and helium sniffer leak detection are presented and applied. The combination of both leak test methods has proven ideal in experimental investigations. For laser remote welding, gas-tight seams can be achieved with an inter-sheet gap of 0.1 mm, even if occasionally leaking samples cannot be prevented. Resistance spot welding suits gas-tight joining with both one- and two-component adhesives. Against the background of leak tightness, process fluctuations that lead to weld spatter and defects in the adhesive layer must be prevented with high priority.

Web-post buckling resistance calculation of perforated high-strength steel beams with elliptically-based web openings for EC3

There has been an increase in the use of high-strength steel, as it provides lightweight structural members by satisfying environmental and economic issues. This paper aims to implement high-strength steels in the web-post buckling resistance equation, which was based on the truss model according to EUROCODE 3, presented previously by the authors. For this task, a finite element model is developed and employing geometrically and materially nonlinear analysis with imperfections. A parametric study is carried out, considering the key geometric parameters that influence the web-post buckling resistance. Three high-strength steel grades are studied (S460, S690 and S960) and in total, 13,500 finite element models are processed. A new factor for adapting high-strength steels to the equation proposed previously was presented. The statistical parameters calculated, via the ratio between the numerical and analytical models, considering the regression, mean, standard deviation and variance, were 0.9817, 0.985, 8.29% and 0.69%, respectively. In conclusion, a reliability analysis was presented based on Annex D EN 1990 (2002).

High-strength steel beams with hexagonal web openings under impact load

A drop-weight impact testing machine was used to conduct an impact test on 15 specimens in order to examine the impact resistance of high-strength (HS) steel beams with hexagonal web openings (SBHWO). The test findings demonstrate that as steel strength increases, maximal impact force and impact platform value rise, while maximum displacement, residual displacement, beam-end rotation, reduction ratio of opening area, and energy absorption ratio decrease. The use of high-strength steel can significantly improve the impact resistance of the SBHWO. When steel Q235 was lifted to steel Q550, the average increase of impact peak and impact platform value was 17.94% and 90.80%, respectively, and the average reduction range of maximum displacement and residual displacement in the span was 45.36% and 55.30%, respectively. After steel Q550 was upgraded to steel Q690, the improvement effect of impact resistance is small. Empirical equations of the relationship between impact energy，steel strength and dynamic responses were established.

Quantitative tests revealing hydrogen-enhanced dislocation motion in α-iron

Hydrogen embrittlement jeopardizes the use of high-strength steels in critical load-bearing applications. However, uncertainty regarding how hydrogen affects dislocation motion, owing to the lack of quantitative experimental evidence, hinders our understanding of hydrogen embrittlement. Here, by studying the well-controlled, cyclic, bow-out motions of individual screw dislocations in α-iron, we find that the critical stress for initiating dislocation motion in a 2 Pa electron-beam-excited H2 atmosphere is 27-43% lower than that in a vacuum environment, proving that hydrogen enhances screw dislocation motion. Moreover, we find that aside from vacuum degassing, cyclic loading and unloading facilitates the de-trapping of hydrogen, allowing the dislocation to regain its hydrogen-free behaviour. These findings at the individual dislocation level can inform hydrogen embrittlement modelling and guide the design of hydrogen-resistant steels.