Large Steel Research Articles

Scale test of large space stainless steel structure subjected to natural fire

Stainless steel is increasingly being used in architectural structures, especially in large space structures which pursue artistic effects. Although stainless steel has better fire resistance than carbon steel, fire retardant coatings are rarely used for stainless steel structures. Based on the 11th Jiangsu Horticultural Expo, a 1:4 scale model was established to explore the fire behaviour of large space stainless steel structures. The air temperature, structural temperature, thermal radiation and structural displacement were investigated. The research showed that air temperature above the fire source was radial. With distance from the fire source increasing, air temperature dropped faster and faster. The structural temperature showed a linear increase during combustion. For the members not directly exposed to fire, the temperature was generally less than 100 °C. While the temperature of the members directly exposed to fire reached up to 200 °C. During the whole test, the large space stainless steel structure was in an elastic stage. The displacement of both ends of the member directly above the fire source was the largest. The structure on the side where the fire source was placed moved upwards and that on the other side moved downwards. When each test finished, the structural displacement was restored to the original state taking about two hours. The test results showed that the large space stainless steel structure was safe when subject to the natural fire during the normal service. Detailed test methods are provided herein, which offers a significant reference for similar research on large space steel structures.

Towards the automated virtual trial assembly of large and complex steel members using terrestrial laser scanning and BIM

Virtual Trial Assembly (VTA) is proposed as an alternative to physical trial assembly that can significantly reduce cost and time requirements. Existing studies on VTA can be categorized as total station and camera-based methods or Terrestrial Laser Scanning (TLS)-based methods. The real coordinate measurement procedure in existing total station and camera-based VTA methods is inefficient and complex because many targets have to be manually installed at assembly points and because different members require different installation schemes. Existing TLS-based VTA methods involve significant human intervention because assembly point extraction and assembly simulation are achieved with commercial software. In addition, geometric quality inspection is not performed in TLS-based VTA methods, although the basis for VTA is the dimensional quality compliance of the components. Therefore, this study presents an automated approach to perform VTA for large and complex steel members based on TLS, and Building Information Modeling (BIM) is utilized to provide as-designed geometric data. Specifically, an automated method is presented to extract assembly points. An internal point removal method is proposed for a BIM model to improve the accuracy of fine registration. A geometric quality inspection method is developed for bending and torsional deviation inspection. The proposed approach is found to be reliable through its application to a practical super high-rise building.

Physical Modelling of High Stiffness Large Diameter Steel Tubular Pile Subjected to One-Way Horizontal Cyclic Loading

Two centrifuge model tests were conducted, each with three large diameter steel tubular piles installed under similar conditions, i.e., diameter (Φ) = 2 m; thickness (t) = 25 mm; loading height from the rock surface (HL) = 6.5 m, but different rock socketing depths (dr), i.e., 2 m, 3 m, and 4 m, respectively, in prototype scale. Two additional 1 g model tests were conducted using the same model pile and ground. The results indicate that the pile lateral resistance increased with an increase in the rock socketing depth to diameter ratio (dr/Φ) in both 1 g and 50 g models. However, the difference between the two gravitational acceleration levels became visible in the non-linear behaviour as the imposed displacement increased. Specifically, the 1 g models showed larger residual displacement and less stiffness in reloading than the 50 g models, particularly under cyclic loading. Two types of ultimate failure modes were observed, i.e., rock failure and pile structural failure with local buckling just above the rock surface. The latter failure mode was only attained in the pile with a dr/Φ ratio of 2 in a 50 g models among the test conditions adopted in the models, but not in the 1 g model.

Experimental and numerical investigation on the deformation behaviors of large diameter steel tubes under concentrated lateral impact loads

Large diameter steel tubes are widely used in bottom fixed and floating offshore wind turbines. Offshore wind turbines (OWTs) operating in the oceans are exposed to the risk of collisions when ships pass and dock at turbines. Thus, it is extremely important to investigate the impact mechanics of ship-OWT collisions and propose practical designs for methods to protect OWTs from collision loads. This paper presents a series of experimental and numerical studies on the deformation behaviors of large diameter steel tubes from a NREL 5 MW spar-type floating offshore wind turbine (FOWT) under lateral impact loads. These studies consider the effects of different impact velocities, attached masses, diameters and thicknesses of the tubes on their response to impact loading. In these experiments, a rigid indenter was mounted on a pendulum system and accelerated to strike the tubes; the scale was 1:30. The dimensions of the indenter head were much smaller than the tube diameter in order to concentrate the impact load. Global motions of the impacted tubes were modeled by springs introduced at the boundaries, and their stiffnesses were determined according to an equivalent single-degree-of-freedom (SDOF) model. Numerical simulations of the experiments were conducted using the nonlinear finite element (FE) software LS-DYNA. The experimental and numerical results were compared and discussed with respect to force-deformation curves, deformation modes and energy dissipation. Existing theoretical solutions for the lateral indentation resistance of tubes were also compared to the experimental and numerical simulation data. The results indicated needs for new solutions when the impact loads become concentrated.

3D Numerical Modeling of Molten Steel Flow and Inclusion Transports During the Solidification Process of a Large Steel Ingot

3D Numerical Modeling of Molten Steel Flow and Inclusion Transports During the Solidification Process of a Large Steel Ingot

Drill string dynamic characteristics simulation for the ultra-deep well drilling on the south margins of Junggar Basin

Improper drilling parameters may cause severe vibration of drill string which leads to reduce the rate of penetration and drilling tool premature failure accidents in the drilling process of ultra-deep well. The study on dynamic characteristics of drill string plays an important role in increasing the safety of drilling tool and optimizing the drilling parameters. Considering the influences of real borehole trajectory, interaction between bit and formation, contact between drill string and borehole wall, stiction of drilling fluid and other factors, a comprehensive drill string dynamic model was established to simulate the changes of wellhead hook load, torque, equivalent stress of drill string and BHA (bottom-hole assembly) section acceleration and motion trajectory with time at different WOBs (weights on bit) and rotary speeds. The safety factor and overpull margin of wellhead drill string were calculated and the strength of drilling tool in ultra-deep well was checked using the fourth strength theory. The analysis results show that, in the drilling process of ultra-deep well, the transverse motion amplitude of the drill string near the wellhead is relatively small and vibration of drill string mainly occurs in the lower well section. As the rotary speed increases, the number of collision between lower drilling tool and borehole wall increases, wellhead transverse stress increases, change in torque is not large and change in wellhead equivalent stress is relatively small. As the WOB increases, wellhead torque will increase, axial load and equivalent stress will decrease and vibration acceleration of BHA will increase sharply. Wellhead overpull margin and safety factor will decrease with the increase of rotary speed and increase with the increase of WOB. Wellhead safety factor of S135 drilling tool in an Φ190.5mm ultra-deep well on the south margins of Junggar basin changes around 1.8. The drilling tool is safe and has relatively sufficient ability to deal with the downhole accidents if a large size high steel grade drill string (Φ139.7mm S135) is used. However, in view of BHA safety, neither rotary speed shall be too high nor WOB shall be too large.

Improving microstructure and segregation of steel ingot by inorganic heat absorption method

A novel method by adding inorganic heat absorption material (IHAM) into the molten steel was proposed to improve the quality of large steel ingots. The IHAM was found to melt and float up after absorbing the heat of molten steel, stirring the melt and thus accelerating the cooling process. The molten steel was also purified as the inclusions were adsorbed during the floating of IHAM. The addition of IHAM rod was conducive to increase the equiaxed grain ratio (EGR) and alleviate the central carbon segregation, while the IHAM cored wire played a more important role in reducing the inclusion index. This method holds broad appeal to solidification of large steel ingot, as it can improve the microstructure of solidified ingot.

Solidification Principle in Large Vertical Steel Casting Under the EMS Effect

The surging demand for large high-quality rotor shafts or similar steel components in heavy industries (energy sector) poses new challenges to steelmakers. Based on the experience of conventional ingot and continuous casting, several new process concepts have been proposed, e.g., vertical continuous casting (VCC), semi-continuous casting (SCC), and segment casting (SC), but none of them are optimally put in operation. The main problems include the control of the as-cast structure and macrosegregation. Electromagnetic stirring (EMS) is necessary to obtain the center equiaxed zone, but EMS-induced multiphase flow can cause severe macrosegregation and uneven distribution of the as-cast structure between equiaxed and columnar. In this study, an advanced mixed columnar-equiaxed solidification model was used to investigate the formation of the as-cast structure and macrosegregation in an example of SCC with a large format (diameter 1 m). The main role of EMS is to create crystal fragments by fragmentation, which is regarded in this work as the only origin of equiaxed grains. The created equiaxed grains are brought by the EMS-induced (primary and secondary) flow and gravity-induced sedimentation to the central/lower part of the casting. The main goal of this study was to understand the solidification principle of SCC. In addition, a numerical parameter study by varying the EMS parameters was also performed to demonstrate the model capability towards the process optimization of SCC.

Industry 4.0 maturity and readiness assessment: an empirical validation using Confirmatory Composite Analysis

Manufacturing enterprises’ business operations are expected to be significantly transformed by Industry 4.0 technologies. However, due to a lack of solid assessment framework and procedures to evaluate the current status and readiness to change in the academic literature, many manufacturing firms frequently fail to assess, assimilate, or struggle to implement Industry 4.0 technologies and processes. To fill this need, this research proposes a novel multi-dimensional analytical framework and indicators for assessing Industry 4.0 maturity and preparedness. This framework include-six dimensions and 32 indicators that have been tested with reference to a large multinational steel manufacturing company. The study employed CCA and IPMA analysis techniques to validate the survey data from the case company. The results support and verify the status wherein the supply chain dimension has the highest performance, and the business model dimension has the lowest in terms of Industry 4.0 maturity and readiness status. The framework and index thus developed have practical relevance as it is easy to understand, interpret and validate in any other manufacturing organization. Furthermore, this study is the first to apply the structural equation modelling technique, i.e. CCA and IPMA, to evaluate Industry 4.0 maturity and readiness from a developing country perspective in the context of steel manufacturing.

Evaluation of the Szapáry Long-Span Box Girder Bridge Using Static and Dynamic Load Tests

This paper presents the results of a recent field test carried out before the opening phases of the Szapáry motorway bridge across the Tisza River in central Hungary. The evaluation test was based on static and dynamic load tests that provided information on deflection, stresses, and dynamic mode shapes along the bridge. The structure has two large continuous independent steel box girders that cover spans across the floodplain and river. Various configurations of truck loading applied up to 6400 kN of loading on the deck. During the static tests, string potentiometers recorded deflections at mid-span. Additionally, strain gauges enabled strain/stress measurements at the mid-point of the longest span and directly above one support. Dynamic loadings showed variation in deflection response due to vehicle speed, and ambient vibration testing led to determining vibration modes and frequencies. A three-dimensional finite-element model produced similar deflections, stresses, and modal behavior. Measured and modeled deflections and stresses indicated that the bridge performed within design margins. The testing and analysis results will be part of a future program assessing conditioned-based maintenance.

Modelling of spatial distribution of segregations in large steel ingots by analysis of centimetric segregation maps

Mesosegregation appears during the solidification of low-alloyed steels at the scale of a few grains. It causes chemically segregated bands in forgings manufactured from steel ingots. As this may affect the mechanical properties of the produced parts, it is crucial to understand the formation of such segregation patterns. While both microsegregation and macrosegregation are well understood and can be readily characterized, little is known about the formation of mesosegregation. In this paper we present a data analysis method to identify the characteristic scales and patterns of mesosegregation. Segregation was mapped on centimetric samples, using micro X-Ray fluorescence (µXRF). The fine sampling grid used reveals segregation patterns at different scales. To identify and distinguish the mesoscale segregation patterns from smaller and larger present patterns, a numerical data analysis technique based on spatial filtering was used. It can identify characteristic scales of mesosegregation patterns on 2D serial cut samples, leading to 3D reconstruction. This approach combined with simulation studies, will ultimately pave the way to a comprehensive understanding of the formation of mesosegregation.

Improved Differential Evolution Algorithm for Slab Allocation and Hot-Rolling Scheduling Integration Problem

To reduce logistics scheduling costs and energy consumption, this paper studies the slab allocation and hot-rolling scheduling integrated optimization problem that arises in practical iron and steel enterprises. In this problem, slabs are first allocated to orders and then sent to heating furnaces for heating; then, they are sent to a hot-rolling mill for rolling. A 0–1 integer programming model is established to minimize the attribute difference in the allocation cost between slabs and orders, the switching cost of hot-rolling processing, and waiting times after slabs reach rolling mills. Given the problem’s characteristics, an improved differential evolution algorithm using a real-number coding method is designed to solve it. Three different heuristic algorithms are proposed to improve the quality of solutions in the initial population. Multiple parent individuals participate in the mutation operation, which increases the population diversity and prevents the algorithm from falling into the local optimum prematurely. Experiments on 14 sets of real production data from a large domestic iron and steel plant show that our improved differential evolution algorithm generates significantly better solutions in a reasonable amount of time compared with CPLEX, the simulated artificial method, and the classical differential evolution algorithm, and it can be used by practitioners.

Virtual trial assembly of large steel members with bolted connections based on point cloud data

Virtual trial assembly (VTA), an alternative to physical trial assembly, has been used in many projects owing to its advantages of low time consumption and low cost. However, the existing methods based on the terrestrial laser scanner (TLS) have low precision, are inefficient, and cannot guide rectification, making them impractical for large steel members with bolted connections. Therefore, this study introduces an automated approach to perform VTA using 3D laser scanning technology and building information modeling (BIM). In particular, a multi-scale data acquisition scheme that integrates a TLS and hand-held scanner is proposed to collect high accuracy point cloud data (PCD). Moreover, a rectification scheme based on particle swarm optimization is developed for gusset plates to guide rectification, and two efficient registration methods are established to align the scanned PCD with BIM model. The accuracy and feasibility of the proposed method are demonstrated through application to an actual suspension bridge.

Static Design for Laterally Loaded Rigid Monopiles in Cohesive Soil

Rigid monopiles with small slenderness ratios (i.e., ratio of monopile embedded length to outer diameter) are widely used as foundations to resist lateral load and moment transferred from superstructures, e.g., large diameter steel pipes used by offshore wind turbines and piers in electric utility industry or sound barriers. A design model for laterally loaded rigid monopiles in cohesive soil is presented in this paper. The proposed design model assumes a constant depth of rotation point as well as a trilinear distribution model of soil lateral reaction along the embedded length of the monopile, and introduces a mobilization coefficient of soil reaction to quantify the magnitude of soil reaction mobilized under a certain load applied at the monopile head. The relationship between the mobilization coefficient and monopile head rotation is established by back-analyzing test results measured from series of laterally loaded pile tests, and then a general design procedure for a laterally loaded rigid monopile in cohesive soil is recommended. The feasibility and reliability of the proposed design model is validated against three cases of numerical simulations on laterally loaded piles in cohesive soils. It shows that this study’s proposed design model produces a relatively satisfactory prediction of the nonlinear load-deformation response, and can be used for laterally loaded monopile design in the sites with undrained shear strength being uniform or increasing linearly with depth.

Soil Structure interaction of Laterally Loaded Piles

The rapid development of the global economy has led to an increased energy demand throughout the world. More than 70% of the world’s energy consumption is from the use of fossil fuels. In the wake of rising global temperatures and increased carbon emissions, policymakers across the globe think about alternate and renewable ways of energy generation, among which wind energy is a promising energy source. Offshore wind turbines are new technologies and are challenging when it comes to their installation in harsh ocean environment as they are subjected to environmental loads caused by wind, wave and currents. These loads are then transferred to foundation. Monopiles are the most common foundations used in offshore wind turbines today and therefore its analysis is important. Monopiles are single large diameter tubular steel piles of diameter 3–7 m driven into the seabed with typical penetration depth of 25–30 m, and are subjected to lateral dynamic loads. Soil structure interaction of monopile is an important aspect to be considered in its design and for the present study, PLAXIS 3D geotechnical software is used for the soil-pile interaction and the corresponding displacement behaviour of the pile under study. The dynamic analysis due to the wave forces on the monopile is carried out using wave data off Gulf of Mannar, near the Tamil Nadu coast, and the embedment length of the pile is varied to study the effect of diameter of pile and embedment length on the displacement characteristics of the pile.

Riverine distribution and abundance of Japanese eel in Shikoku, south‐western Japan: Varying importance of regional and local factors

Abstract Regional and local habitat factors affecting the distribution and abundance of Japanese eel (Anguilla japonica) were systematically analysed in 123 reaches of 21 stream systems in south‐western Japan, with particular attention paid to human habitat modification, such as artificial barriers and concrete revetment. The density of Japanese eel decreased upstream, and they were absent from the upper reaches of each stream system. The upper limits of their distribution were explained by the distance from the sea and the channel gradient, rather than barriers. However, the number of barriers had the highest explanatory capacity for the upstream decline in abundance of small eels (<40 cm in total length). Analyses of the relative importance of regional and local habitat factors showed that the number of barriers (regional factor) was more important than local habitat factors in determining small eel abundance, whereas regional and local habitat factors (e.g. concrete revetment or cover habitat) were similarly important for large eel abundance. These results suggest that: (i) barriers are not a major factor limiting the distribution (presence/absence) of the Japanese eel in the streams studied; (ii) barriers can substantially decrease the abundance of young eels; and (iii) as eels grow older and larger, local habitat factors, such as bank conditions and cover, become more important in determining their abundance. The results for the relative importance of regional and local habitat factors suggest that in habitat restoration for the Japanese eel, priority should be given to mitigating barrier effects. The improvement of longitudinal connectivity to facilitate colonization by young eels is primarily needed for a more efficient use of the existing carrying capacity of streams. The improvement of local habitat conditions to increase the carrying capacity should be conducted in stream reaches free from barrier effects.

Effect of size grading on growth of yellow Pacific shortfin eel (Anguilla bicolor pacifica).

Heterogeneous growth, which is common among farmed fish, can be remedied by size grading. This study focused on whether the size grading process, which is commonly practiced in aquaculture, improves the subsequent growth performance of the Pacific shortfin eel Anguilla bicolor pacifica. Eels [338.70 ± 4.70 mm total length (TL) and 84.93 ± 1.87 g body weight (BW)] were initially reared for 60 days (pre-size grading period) and manually divided into three size groups: small (≤115 g), large (>150 g) and mixed (>115 g but <170 g), all maintained at a density of 5 kg m-3 and reared until day 150 (size grading period). After size grading, mean BW and TL at harvest significantly differed in all eel groups, suggesting growth was size specific. Nonetheless, at day 150, except for biomass, size grading had no significant effect on growth and survival, coefficient of variation of length and weight, and Fulton's condition factor. Large eels had a significantly higher feed intake than mixed or small eels, whereas feed efficiency did not differ among eel groups. Results suggest that size grading promotes size-specific growth but did not improve the overall growth performance of yellow stage of A. bicolor pacifica.

Dynamic responses of a large fishing net under waves with boundaries deforming with time

The deep-sea aquaculture cages usually consist of large steel frames and large-area fishing nets. The fishing nets are usually mounted on the frames. Under the action of waves, the frames may deflect with time. Then the boundaries of the fishing nets will change with time. In this paper, a nonlinear dynamic model of a large flexible fishing net under the combined excitations of waves and boundary deformations is developed, in which four different cases of boundary deformations are considered. The present model is numerically solved with the Runge-Kutta method. It is validated with the comparisons to experimental and simulation results. Based on the present model, the dynamic responses of a large fishing net under the action of waves and boundary deformations are analysed in detail. The results indicate that when the boundaries of the net are deforming with a large frequency, the vibrations of the net will be significantly affected, and the tensions of twines will largely increase, which is more easily to become failure.

Field tests on large-scale instrumented piles driven in chalk: results and interpretation

The design of large open steel piles driven at chalk sites suffers from considerable uncertainty, leading to major difficulties in many significant onshore and offshore projects. This paper describes recent instrumented driving, monotonic testing to failure, and restrike tests conducted on large open steel piles driven in primarily low- to medium-density chalk at a site in North-western France. The experiments are described and interpreted with reference to a high-quality site characterisation, dynamic and static methods of test analysis, and alternative predictive design approaches. Important new conclusions flow regarding driving behaviour, the set-up that took place over up to 65 days after installation and the resistances available under compression and tension loading. Surprisingly large differences are shown between tension and compression shaft capacity, which are postulated to be due to Poisson straining in the steel pile shaft and its interaction with the surrounding chalk mass. The field tests contribute to building a high-quality dataset that allows proposed axial capacity design methods to be tested and potentially refined to provide reliable and representative design tools.

Experimental and numerical analyses of residual stress redistributions in large steel dies: Influence of tempering cycles and rough milling

The aim of the present research was to study the residual stress variations induced by heat treatment and rough milling operations of large forged steel blocks. The heat treatment process includes quenching and tempering operations. An efficient strategy based on a size sensitivity analysis (SSA) was proposed to reach the actual values of residual stresses in large-size steel blocks by using small-size workpieces in laboratory scale without damaging the blocks. The residual stresses were measured and compared after the first and second tempering and the rough milling. A 3D finite element (FE) model was developed to predict superficial residual stresses and was then calibrated experimentally. The results showed that the residual stresses after the first and second tempering were highly compressive on and near the surface. In addition, the resultants of the residual stresses after double tempering processes were almost equal. Therefore, the second tempering could be omitted from the manufacturing process. It was also found that both surface and sub-surface hoop and radial residual stresses were highly tensile after the rough milling. Finally, the 3D FE model can be used as a predictive tool to predict residual stresses for rough milling to avoid conducting expensive, time-consuming experimentations and measurements.