Levels of lateral flange bending in straight, skewed and curved steel I -girder bridges during deck placement

Exterior steel I-girders are required to withstand deck overhang loads during construction. This is partially accomplished by checking the flexural limit states for constructibility given by AASHTO. These limit states ensure that the maximum flange bending stresses produced during construction do not exceed the section flexural capacity of the girder.;For constructibility design, both the bending stresses and the flexural capacity of the flanges are affected by the loads corresponding to the deck placement sequence. Therefore, stiffness changes need to be considered during the various casting stages to compute the corresponding flange bending stresses and capacities. The specifications take into account this effect by defining separate limit states for discretely and continuously braced flanges. The limit states for discretely braced flanges involve not only the major-axis bending stresses produced by vertical loads but also the lateral flange bending (LFB) due to torsional responses or direct horizontal forces such as those produced by wind.;During construction, torsional effects are principally generated on exterior girders by deck overhang loads. In curved girders, it is also required to consider the significant torsional stresses introduced by the curvature, where the loads are eccentric with respect to the supports. Additionally, direct LFB may be induced in skewed bridges at cross-frame locations caused by differential displacements or out-of-plane rotations.;Some simplified models have been proposed to estimate the LFB in exterior girders during deck placement conditions in straight bridges. However, the use of comprehensive models decreases the uncertainty in the lateral stiffness offered by structural elements such as the cross frames, the interior girders and the deck forms. In addition, the curvature and the skew angle effects have not been directly addressed in these simplified works.;AASHTO Specifications recommend approximate equations to estimate the torsional effects due to both deck overhang loads and curvature. For skewed bridges, the provisions recommend using 10Ksi as a conservative estimation of the unfactored LFB in bridges with discontinuous cross-frame lines and skew angles exceeding 20°. However, more precise approximations may be defined for each source of LFB if effects such as the continuity over the intermediate supports and the deck casting sequence are considered.;In this work, a comprehensive suite of finite element analyses is conducted on hypothetical three-span straight, skewed and curved bridges to assess the levels of flange bending during deck placement. The parameters varied include the span lengths, the cross-frame spacing, the skew angle and the radius of curvature. In addition, concentrated and distributed loading cases are considered to approximate the torsional effects due to eccentric overhang loading. A comprehensive formulation of the LFB effects due to curvature is also included for both loading cases. Numerical results were compared to current AASHTO Specifications and new approximations were proposed for predicting the LFB stresses. The flexural limit states for constructibility were also evaluated using the numerical stresses.;It was concluded that the curvature is the variable that most affects the limit states. Conversely, for the parameters exercised in this study, no significant effects were observed by varying the skew angle. The governing limit state of the casting sequence considered in this study corresponds to the ultimate strength for discretely braced flanges in compression. The yielding limit state controls in short span lengths while the web bend-buckling limit state becomes significant in the pier regions for long span lengths.;AASHTO does not include a specific recommendation for the spacing of cross frames in steel bridges. Therefore, the designer needs to either evaluate different configurations to select the most optimum spacing, or follow traditional practice that assures safe results. For that reason, a reliability analysis was proposed in this work to develop a practical method to select the cross-frame spacing for deck placement conditions considering the flexural limit states for constructibility that are affected by the cross-frame spacing. A Monte Carlo Simulation is performed for straight, skewed and curved steel I-girder bridges generating some fragility curves that allow identifying the maximum cross-frame spacing for deck-placement conditions according to the maximum tolerated level of risk

Título: Crónica de don Juan II

Obra atribuida a Fernan Perez de Guzman, a Lucio Marineo Sículo segun Palau o a Alvar Garcia de Santamaria por otros.Sign.: []2, *-(5)*2, A-3Z4, 4A-4C4, 4D1, 4E2-4E4, 4E-4G4, 4H-402Texto a dos col.Port. con grab. calc.Antep.Error tip. en el segundo cuadernillo 4E2-4E4 que tendria que ser 4D2-4D4.Grab. calc.: "Rafael Ximeno delineó, Mariano Brandi gravó", retrato de Enrique III, en p.1Grab. calc.: "Rafael Ximeno delineó, Mariano Brandi gravó", retrato de Juan II, en p.23Contiene: Generaciones y semblanzas de los señores reyes don Enrique III y don Juan II ..

Anisotropic magnetotransport realized in doped hematite

Conventional antiferromagnetic materials have long been recognized for their time-reversal symmetry, resulting in a zero anomalous Hall coefficient. However, a paradigm shift occurs when examining easy-axis antiferromagnets and their spin-flop transition. This transition introduces a magnetic canted moment, leading to the emergence of a non-zero anomalous Hall signal and the generation of a non-dissipative transversal current. While high symmetry systems typically manifest an isotropic Hall effect, our study unveils the extraordinary behavior exhibited by hematite that becomes conductive due to small Ti doping. We investigate the magnetotransport in Titanium-doped hematite, uncovering a highly pronounced and unconventional symmetry. Notably, this effect displays a remarkable dependence on the crystal orientation of the material. We establish a compelling correlation between our experimental observations and the predicted anomalous Hall effect in altermagnets through symmetry analysis. This study expands our understanding of the Hall effect in antiferromagnetic materials and sheds light on the intricate interplay between crystal orientation and unconventional Hall phenomena

Whole Genome Sequencing and Evolutionary Analysis of Human Respiratory Syncytial Virus A and B from Milwaukee, WI 1998-2010

BACKGROUND: Respiratory Syncytial Virus (RSV) is the leading cause of lower respiratory-tract infections in infants and young children worldwide. Despite this, only six complete genome sequences of original strains have been previously published, the most recent of which dates back 35 and 26 years for RSV group A and group B respectively. METHODOLOGY/PRINCIPAL FINDINGS: We present a semi-automated sequencing method allowing for the sequencing of four RSV whole genomes simultaneously. We were able to sequence the complete coding sequences of 13 RSV A and 4 RSV B strains from Milwaukee collected from 1998-2010. Another 12 RSV A and 5 RSV B strains sequenced in this study cover the majority of the genome. All RSV A and RSV B sequences were analyzed by neighbor-joining, maximum parsimony and Bayesian phylogeny methods. Genetic diversity was high among RSV A viruses in Milwaukee including the circulation of multiple genotypes (GA1, GA2, GA5, GA7) with GA2 persisting throughout the 13 years of the study. However, RSV B genomes showed little variation with all belonging to the BA genotype. For RSV A, the same evolutionary patterns and clades were seen consistently across the whole genome including all intergenic, coding, and non-coding regions sequences. CONCLUSIONS/SIGNIFICANCE: The sequencing strategy presented in this work allows for RSV A and B genomes to be sequenced simultaneously in two working days and with a low cost. We have significantly increased the amount of genomic data that is available for both RSV A and B, providing the basic molecular characteristics of RSV strains circulating in Milwaukee over the last 13 years. This information can be used for comparative analysis with strains circulating in other communities around the world which should also help with the development of new strategies for control of RSV, specifically vaccine development and improvement of RSV diagnostics

Intermetallic-Rich Layer Formation for Improving Corrosion Resistance of Magnesium Alloys

Abstract: The present work examines the formation of a corrosion protective coating containing intermetallic phases on magnesium alloy substrates. The protective coating was formed on the surfaces of commercially pure magnesium (cp Mg) and AZ31B magnesium alloy by vacuum thermal evaporation of commercially pure aluminium (cp Al) and a subsequent heat treatment of the sample. This coating was continuous, homogenous and its microstructure was a eutectic phase composed by clusters of α-Mg surrounded by β phase (Mg17Al12). This eutectic-type coating provided 168 and 504 h of protection inside the salt spray chamber for the cp Mg and AZ31 alloy samples, respectively. To achieve this, it was required to deposit at least 5.5 µm of cp Al and then perform a combined thermal treatment involving heating the samples to 583 K for 60 min and then raising the temperature to 693 K for 5 min. Graphic Abstract: [Figure not available: see fulltext.] © 2021, The Korean Institute of Metals and Materials

Improved Mg–Al–Zn Magnesium Alloys Produced by High Energy Milling and Hot Sintering

Abstract: Powders of commercially pure magnesium (c.p. Mg), AZ91 magnesium alloy and zinc were milled using a high-energy mill. The effect of high energy milling (HEM) on powders morphology, chemical composition, crystallite size and compaction of different powders mixtures were studied. After compaction, samples were thermally treated at 450 °C and both density and hardness were evaluated. It was found that as milling speed and time increases, the AZ91 alloy and c.p. Mg particles were deformed and fractured up to sizes below 10 ?m. X-ray diffraction patterns for both the c.p. Mg and the AZ91 powders revealed that the milling process induced changes in both the ?-Mg and the ?-Mg17Al12 phases. By increasing the milling speed, the crystallite size decreases by up to 70% for AZ91 powders and by 80% for magnesium powders. The relative densities of the compacted AZ samples were greater than 85% and this parameter increased for all samples after thermal treatment at 450 °C, obtaining densities higher than 88%. Hardness measurements disclosed values as high as 84.3 HR15T. Theoretical calculations of mechanical strength were obtained for all samples based on the hardness values measured, finding very encouraging results for the three Mg alloys. Graphic Abstract: [Figure not available: see fulltext.]. © 2019, The Korean Institute of Metals and Materials

New insights on the influence of low frequency pulsed current on the characteristics of PEO coatings formed on AZ31B

In this work, anodic oxide layers on the surface of an AZ31 magnesium alloy were obtained by plasma electrolytic oxidation (PEO) process under low frequency pulsed current. For this, electrolytical solutions containing hexamethylenetetramine and sodium fluoride were used. The morphology and chemical composition of formed coatings were examined by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). Also, salt spray test, hydrogen evolution and electrochemical tests (potentiodynamic polarization and electrochemical impedance spectroscopy) were conducted in order to study the corrosion behavior of the coated samples. It was found that the use of low frequency pulsed current for the PEO process reduces the film porosity and increases its thickness, compared with PEO films obtained by continuous anodization. The effect of the pulsed current signal was also analyzed for a two steps PEO process, observing changes in the morphological characteristics of the coatings which allow a better corrosion according electrochemical tests (short term corrosion measurements). However, long term tests results as hydrogen evolution and salt spray tests, indicated the opposite. Both the film porosity and thickness were affected by either the pulsing of the current or the use of a two-step process. © 2020 The Author(s). Published by IOP Publishing Ltd