52,064 research outputs found
Turbulence, Inequality, and Cheap Steel
No full textIron and steel production grew dramatically in the U.S. when mass production technologies for steel were adopted in the 1860s. According to new measures presented in this study, earnings inequality rose within the iron and steel industries about 1870, perhaps because technological uncertainty led to gambles and turbulence. Firms made a variety of technological choices and began formal research and development. Professional associations and journals for mechanical engineers and chemists appeared. A national market replaced local markets for iron and steel. An industrial union replaced craft unions. As new ore sources and cheap water transportation were introduced, new plants along the Great Lakes outcompeted existing plants elsewhere. Because new iron and steel plants in the 1870s were larger than any U.S. plants had ever been, cost accounting appeared in the industry and grew in importance. Uncertainty explains the rise in inequality better than a skill bias account, according to which differences among individuals generate greater differences in wages. Analogous issues of inequality come up with respect to recent information technology.technological change, Bessemer steel, technological uncertainty, turbulence, inequality, innovation
Stainless steel in Sweden : antidumping attacks, good international citizenship
No full textThis report analyzes the economics, legal, and business logic of the United States, Sweden, and the European Community regarding the stainless steel industry. Trade policies and legal cases are analyzed and presented to support the author's conclusion that good economics, international competitiveness, private ownership, and limited support from a government that demonstrates good international citizenship are not enough to defend an industry against the application of antidumping or other import-restricting policy.Water and Industry,Roads&Highways,Primary Metals,Banks&Banking Reform,Mining&Extractive Industry (Non-Energy)
Behaviour and design of composite beams subjected to negative bending and compression
No full textThis paper investigates the behaviour of steel–concrete composite beams subjected to the combined effectsof negative bending and axial compression. For this study, six full-scale tests were conducted on compositebeams subjected to negative moment while compression was applied simultaneously. The level of the appliedaxial compression varied from low to high. Following the tests, a nonlinear finite elementmodel was developedand calibrated against the experimental results. The model was found to be capable of predicting the nonlinearresponse and the ultimate failure modes of the tested beams. The developed finite element model was furtherused to carry out a series of parametric analyses on a range of composite sections commonly used in practice.It was found that, when a compressive load acts in the composite section, the negative moment capacity of acomposite beamis significantly reduced and local buckling in the steel beamismore pronounced, compromisingthe ductility of the section. Rigid plastic analysis based on sectional equilibrium can reasonably predict the combinedstrength of a composite section and, thus, can be used conservatively in the design practice. Detailingwithlongitudinal stiffeners in the web of the steel beam in the regions of negative bending eliminate web bucklingand increase the rotational capacity of the composite section. Based on the experimental outcomes and the finiteelement analyses a simplified design model is proposed for use in engineering practice
Effect of interlamellar spacing on the elastoplastic behavior of C70 pearlitic steel: Experimental results and self-consistent modeling
No full textThe effect of pearlite microstructure characteristics on strength and deformation of C70 pearlitic steel was investigated. Tensile tests under X-ray diffraction coupled with self-consistent model have been used to identify the role of interlamellar spacing on the ferrite plasticity parameters and residual stress induced by plasticity. Tests have been carried out on two pearlitic microstructures with interlamellar spacing Sp = 170 and 230 nm respectively. Ferrite critical shear stresses ðs0c ðaÞÞ are equal to 75–86 MPa for interlamellar spacing Sp = 230 nm and 105–120 MPa for interlamellar spacing Sp = 170 nm. Moreover, the compressive residual stress measured in ferrite phase is higher in elasto-plastically deformed sample (total strain of E11 = 1.2%) having larger interlamellar spacing (rR Fea ¼ 161 MPa for Sp = 230 nm and rR Fea ¼ 77 MPa for Sp = 170 nm)
Microstructure investigation and flow behavior during thixoextrusion of M2 steel grade
No full textThe microstructure investigation and flow behavior during thixoforging of M2 steel parts were investigated. Partial remelting was performed at processing temperatures ranging from 1290 ◦C to 1340 ◦C corresponding to a liquid fraction range between 10% and 30% (according to differential scanning calorimetry measurements and quantitative image analyses). A conventional microstructure for thixoforming process was obtained: spherical solid grains surrounded by liquid phase. The microstructure across the heated billets was relatively homogeneous with bigger grain size near the surface. Successful thixoextrusion for producing parts was finally achieved at processing temperatures. By investigating the microstructure and load-displacement curves, different mechanisms in various forming stages were proposed
Economic viability of demountable steel-concrete composite beams
No full textComposite beams are commonly used in current design practice due to their efficient material use and competitive execution. The shear connection is mainly achieved by means of headed studs welded on the top flange. However, the welded connectors obstruct the possibility of a non‐destructive disassembly required to reuse the steel beams and concrete slabs. Raised concern regarding sustainability aspects drive the construction sector to introduce a shear connector which enables the demountability of the flooring. Composite action can be enabled by a bolted connection consisting of an embedded bolt and coupler connected by an external injection bolt through the top flange of the steel beam. This paper aims to assess the initial investment costs and economic viability of two demountable steel‐concrete composite beam solutions. The investigated systems comprise of two different concrete flanges: a prefabricated solid deck and an in‐situ casted profiled sheeting slab. The cost inputs of the analysis were defined by industry experts based on assumed labour and material requirements. The unit price of the novel connector is significantly higher (approx. 15 times) compared to the regular headed welded stud. This justifies the need to optimize the connector arrangement in order to keep the cost per square meter as low as possible. Non‐uniform connector arrangements can be used to reduce construction time and costs with minor decrease in beam stiffness. A tool was developed to generate a batch of 13500 composite beam designs which were later analysed in terms of costs.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Steel & Composite Structure
An alternative design of steel-concrete-steel sandwich beam
No full textA steel-concrete-steel sandwich beam represents a special form of sandwich structure. Originated in civil/structural engineering applications, it is now being developed for shipbuilding/offshore applications. The research trend is to introduce either a new shear connector system or a lightweight concrete. This paper presents an alternative construction of steel-concrete-steel sandwich beam in which the new concept design of aligning the shear connector in the inclined direction is proposed. The novel bi-directional corrugated-strip-core system is presented. The possibility of implement this core system using available sandwich construction techniques is presented. The advantages of the novel bi-directional corrugated-strip-core steel-concrete-steel sandwich beam are preliminarily studied in both the unfilled and concrete-filled state. The analytical study based on the force-distortion relationship technique of the repetitive unit cell shows that the transverse shear stiffness of the unfilled sandwich beam depends on the inclined direction of the proposed core. The numerical study of the concrete-filled sandwich beam type also shows the possibility to increase the transverse shear strength
Proof of concept of a demountable steel-concrete flooring system
No full textEnvironmental concerns steerthe construction industry towards more sustainable developmentssuch asdemountable and reusablestructures. Composite structures are a frequent solution for multi-story buildings and bridges, however the use of welded shear connectors requires labour and energy intensive disassembly. Two bays of a demountable flooring systemfor a multi-storey car park building were erected in the laboratory. The flooring system consists of large prefabricated concrete decks connected to taperedsteelbeams. The feasibility of assembly and disassemblyof the flooring system was tested under laboratory condition. Shear interaction was achieved by an embedded bolt and coupler which areconnected to the top flange of the steel beam by an external injection bolt. Oversized holes are used in thetopflangeof the steel beamto accommodate fabricationand executiondeviationsandthedeformations occurringduring construction. Extensive imperfection measurements and finite element models were used to design the oversized hole diameter to 32 mm. Thehole clearance must be compensated either by pretensioning or injecting the bolt-to-hole clearance with an epoxy resinto enable instantaneous composite action underlive loads.Experimental injection of 150 injection bolts confirmsthat epoxyresin can reliably fill the hole clearance, and that the injectionprocess takes30 seconds per bolt.Various non-uniform shear connector arrangementswere considered to minimizeconstruction costs and maximize the speed of execution. The mechanical behaviour of the demountable composite beam was tested experimentally and numerically.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Steel & Composite Structure
Analysis of steel plate shear walls
No full textIn the past three decades the steel plate shear wall (SPSW), also known as the steel plate wall (SPW) has been used in various buildings throughout Japan and North America. In this paper, existing literature on steel plate shear walls is briefly reviewed. An experimental test conducted and reported thereafter by Sabouri-Ghomi and Golhaki in 2008 was simulated using the finite element method to demonstrate pure lateral load-displacement behaviour of a 3-storey SPSW. A good agreement was obtained. The effects of different plate thicknesses and the introduction of a vertical stiffener on post buckling behaviour and ultimate capacity of the steel plate shear walls are demonstrated using finite element methods for single storey models. Results show that increasing the plate thickness up to the certain value (b/t≥400 from the present study), improves both system capacity and post buckling behaviour of the steel plate shear wall
Corrosion Fatigue Crack Propagation Behaviour of a High Strength Low Alloy Steel in a Synthetic Sea Water Environment.
No full textThe corrosion fatigue crack propagation behaviour of a high
strength low alloy steel, N-A-XTRA 70, in a synthetic sea
water solution was tested using S. E. N. specimens subjected
to a loading frequency of 0.1 Hz and a load ratio of 0.6.
In order to simulate the conditions encountered by a thumbnail
type crack several specimens from each of the
microstructural types tested, namely parent plate, heat
affected zone and heat treated material, had their crack
sides covered by transparent plastic covers. Severe overprotection
and slight underprotection conditions were
produced using cathodic protection potentials of -1400,
-1300, -1200 and -700 mV (S. C. E. ).
The Paris relationship da/dN = CLKm was found to be a useful
tool in describing the crack propagation rate data. Results
obtained, presented in the form of plots of log da/dN against
log AK, show that for parent plate, H. A. Z. and heat treated
material, covering the crack sides of specimens produces
enhanced corrosion fatigue crack propagation rates, at
cathodic protection potentials of -1400 and -1300 mV (S. C. E. ),
when compared to non covered specimens. This trend was also
true for H. A. Z. specimens at a potential of -700 mV (S. C. E. ).
For parent plate specimens, however, covering the crack sides
at a potential of -700 mV (S. C. E. ) produced reduced crack
propagation rates over non covered specimens. It is believed
restriced oxygen access may account for these results.
Plots of the Paris exponent m and constant C for the three
microstructures tested produced three lines of the form
m= alnC +b where a and b were found to be dependent upon
material parameters.
Comparison of results with BS 4360: 50D revealed that N-A-XTRA
70 exhibited superior fatigue performance when tested in air
but behaved worse under conditions of free corrosion
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