Metal Superstructure Research Articles

Fatigue life of unified riveted superstructures designed by Transmostproject with the introduction of increased axle loads

The article presents a study of the residual fatigue life of superstructures during the introduction of trains with increased axial loads on bridges with riveted superstructures, designed in the fifties of the last century. Unified metal superstructures have been in relatively heavy duty conditions for more than 60 years. During lcontinuous operation, processes occur in elements and joints that lead to the appearance and development of various damages and varying degree failures of hazard, so it is necessary to decide on the further operation of old bridge spans and their replacement. When determining the fatigue life, the linear addition hypothesis of fatigue damage accumulation was used, taking into account the increase in stresses with the introduction of increased axial loads. As a critical measure of damage, providing a given reliability, the value obtained from the calculation results of several hundred cracks in riveted superstructures of older design standards was adopted. The increase in load from the installation of a ballastless bridge floor is taken into account. To determine the residual fatigue life, fatigue data is used depending on the concentration of stresses magnitude in the attachments of the main truss elements. For a more accurate determination of the rivet joints operation stage, the author carried out a wear-out calculation through operation period. The introduction of heavier train loads will lead to an increase in the accumulation of fatigue damage in the elements. If weak rivets in attachments are found during inspection, they must be replaced with high-strength bolts to increase fatigue life. The author obtained that the residual fatigue life of the span structures designed by Transmostproekt has not yet been fully exhausted even with the introduction of heavy trains with a wagon axle load of 27–30 tons.

Digital beading for a CAD-CAM framework for an implant-supported overdenture: A dental technique.

The analogue technique of making bead lines for a metal superstructure framework for the maxillary implant-supported overdenture (MISO) is created by scribing shallow grooves on the surface of a definitive gypsum cast. This digital technique describes the usage of CAD-CAM technology to make dental bead lines on an intraoral impression without using the gypsum cast. This article is protected by copyright. All rights reserved.

Magnetic resonance imaging investigations in patients with metallic dental prosthesis: "The associated dilemma for medical fraternity and the dentist's role".

Interdisciplinary referrals for dental examination in hospital setups are common before radiotherapy, kidney transplants, or magnetic resonance imaging (MRI). The patients who walk in could be random patients with metallic or porcelain-fused-to-metal prostheses done elsewhere but might require an opinion before the MRI. This leaves quite a responsibility on the consulting dentist to green signal the procedure. There is a lack of evidence in the literature, to confirm the absence of any untoward consequence during such MRI, which might leave the dentist in dilemma. Dental materials' magnetic behavior raises concern regarding whether they are 100% nonferromagnetic; furthermore, the examining dentist might be unaware of the metal used (Co-Cr, Ni-Cr, or trace elements). Clinicians may also come across full-mouth rehabilitated patients with multiple crown-bridge prostheses or metallic superstructure for implant prostheses. Research in the area leaves many unanswered questions because most studies have evaluated artifacts during MRI and are in vitro. Titanium is considered to be safe due to its paramagnetic behavior, whereas the literature does not rule out the probability of dislodgment of other porcelain fused to metal (PFM) prostheses. Due to less reported literature there exists dilemma to ascertain MRI in these patients. An online Google Search, PubMed, and gray literature portray the ambiguity associated with metal and PFM crowns and their magnetic behavior during MRI. Most studies were associated with the artifacts caused during MRI and methods of reducing them under in vitro situations. The concern for dislodgment has also been expressed in a few reports. Certain steps of a pre-MRI checkup and an innovative technique have been discussed to assure patient safety during the MRI. The technique explained is inexpensive and a quick aid that can be executed before the investigation. There is a need to study and understand the magnetic behavior of Co-Cr and Ni-Cr crowns in the presence of various MRI strengths.

Interfacial bond engineering for direct integration of functional oxides with Si and Ge

A new route to oxide synthesis on semiconductors,viaoptimally oxidized metal superstructures, is established. The result is a radical transformation of the oxide film from a polycrystal to a single crystal.

Self-reference Lock-in Thermography for Detecting Defects in Metal Bridge Spans

Introduction. Incipient fatigue damage in the metal superstructures of bridges creates certain threats to the safety of operation. Various methods of non-destructive testing are used for their timely detection and diagnosis. A modern and popular on-the-day solution is the method of infrared (IR) thermography. Due to the specifics of the operation of IR cameras, additional processing of recordings received from these cameras is required to obtain an accurate result. This work aims at presenting a method for processing thermofilms and describing the possibilities of its application under real conditions.Materials and Methods. A method for processing thermographic films was described. It provided detecting temperature anomalies using only information from the camera. The results of its application on the elements of existing metal bridge spans are presented.Results. It is shown that there are temperature anomalies for existing defects. This means that the defects continue to develop, which was confirmed by subsequent observations of their condition. In addition, a case of temperature anomaly in the defect-free external region was identified. This might be a sign of an incipient defect that could not be diagnosed by other methods. If the presence of this defect is confirmed during repeated examinations, it will be possible to diagnose hidden defects that have not yet come to the surface, and/or detect potentially collapsing places.Discussion and Conclusions. The IR thermography performance as a method of non-contact non-destructive testing is shown, as well as its operability on real objects under random load.

Biomimetic Hierarchical Superstructures: Approaches Using Bicontinuous Microemulsions and Electrodeposition

The current challenges in developing novel nanotechnological processes have led us to explore new methods for synthesizing nanomaterials whose functionalities rely on their structural complexity. In this respect, nature has always been a source of inspiration for proposing innovative technologies to improve the quality of life. Hierarchical superstructures (HSS) are of great interest because the self-assembly of low-dimensional nanostructures (up to the macroscale) allows the control and optimization of performance by coupling the properties of the individual blocks. Self-assembled surfactant structures are convenient for HSS synthesis because they provide a confined reaction medium which confers excellent control over the size of the building blocks. Furthermore, bicontinuous microemulsions offer a soft three-dimensional template due to their interconnected nature. Similarly, electrodeposition routes offer fast, robust, clean, and reproducible ways to synthesize metallic and multimetallic HSS. The combination of soft-templating and electrodeposition is a powerful tool for controlling the morphology and composition of the material. This work reviews polymeric, ceramic, and metallic hierarchical superstructures synthesized using bicontinuous microemulsions and electrodeposition techniques and compares them with matching natural patterns. The aim is to show how these synthetic routes can be exploited to obtain efficient biomimetic nanomaterials that improve their properties.

Hierarchical Colloidosomes and Superlattices via Confined Assembly of Polymer-Tethered Inorganic Nanoparticles

Self-assembly of polymer-tethered metal nanoparticle (NP) building blocks is studied via an emulsion interface self-assembly strategy. The results show that the hollow colloidosomes with a highly ordered hexagonal arrangement of metal NP building blocks are obtained. The interparticle distance between the adjacent metal NPs within the hollow colloidosomes can be effectively tuned by adjusting the molecular weight of the polymeric ligands. Interestingly, with an increase in the volume fraction of the internal hexadecane phase, the particular sheet-like superlattices can be formed. Moreover, the prepared colloidosomes can serve as an excellent substrate for the surface-enhanced Raman scattering and have potential application in photothermal therapy. We believe that this study can provide a promising way to fabricate hierarchical ordered metal superstructures, which have potential applications in photothermal therapy, chemical sensors, and biological optical-imaging.

Determination method for metal bridge superstructure replacement priority using strength, economic and operational criteria

The article describes the problem arising from the setting trains with increased axleloads into operation on bridges with superstructures, engineered according to the old design standards. On the railways used riveted metal bridge superstructures, which require replacement due to significant corrosion, mechanical and fatigue damage, due to insufficient carrying load and residual fatigue life to pass the prospective load. Superstructures, designed in the 30s-40s, are more than 80-90 years used in conditions of a relatively difficult operation. During long-term operation, processes occur in elements and joints that lead to the formation and development of various hazard degrees damages, and failures. It is necessary to resolve the further exploitation issue of old bridge superstructures and their replacement. The author has applied the analyzing method of the criteria system, with the account of economic and technical capabilities for replacement priority determination of bridge superstructures. A set of criteria were proposed for solving this problem in digital form. Compiled matrices of pair-wise comparison, the comparison was performed using a relative importance scale with the test significance determination. By the linear algebra methods the eigenvector of matrix components values — local priorities — are calculated for each pair-wise comparisons matrix. As a result of calculations by the proposed criteria, were obtained global priorities for replacing options for riveted metal superstructures made by old design standards. The mathematical apparatus of the criteria hierarchy method is easy to use and allows you to get a solution in digital form, you can use other criteria.

Experimental studies of the energy dissipation processes at the tops of fatigue cracks in the elements of bridge structures

In the article, the authors investigated the possibility of using the thermal control method for diagnosing fatigue cracks in the metal superstructure, determined the necessary parameters for that control method. The studies were conducted during cantilevered steel samples fatigue tests simulating the superstructure beam wall operation, reinforced with stiffening ribs. To carry out the experiments were developed a test setup and a loading procedure at the various intensity of exposure. An electric motor with eccentrics is used as a loading device. The sample surface heating was recorded by thermal imagers with 0.03 K and 0.05 K temperature sensitivities and 60 frames/s and 9 frames/s shooting speed, respectively. Was confirmed the possibility of determining crack presence before its emergence to the surface namely at the stage of its initiation, and also were determined the self-heating zone dimensions at the tip of a crack. The conducting a laboratory experiment technique on the dissipative processes study in the metal superstructure elements is described.

Nanorod alignment for optical asymmetry

Plasmonics The high polarizability of chiral nanoassemblies of plasmonic nanoparticles can lead to strong chiral dichroism, but strong light scattering causes the fraction of polarized photons generated, as measured by g-factors, to be much lower than that for chiral liquid crystals. Lu et al. used supramolecular interactions of gold nanorods with human islet amyloid peptides to assemble metallic superstructures with unusually high cholesteric order (see the Perspective by Nam and Kim). The long, straight helices increased the g-factor by 4600-fold, and this effect was used to screen small-molecule binding to amyloids. Science , this issue p. [1368][1]; see also p. [1311][2] [1]: /lookup/doi/10.1126/science.abd8576 [2]: /lookup/doi/10.1126/science.abg9901

Enhanced optical asymmetry in supramolecular chiroplasmonic assemblies with long-range order.

Chiral assemblies of plasmonic nanoparticles are known for strong circular dichroism but not for high optical asymmetry, which is limited by the unfavorable combination of electrical and magnetic field components compounded by strong scattering. Here, we show that these limitations can be overcome by the long-range organization of nanoparticles in a manner similar to the liquid crystals and found in helical assemblies of gold nanorods with human islet amyloid polypeptides. A strong, polarization-dependent spectral shift and the reduced scattering of energy states with antiparallel orientation of dipoles activated in assembled helices increased optical asymmetry g-factors by a factor of more than 4600. The liquid crystal-like color variations and the nanorod-accelerated fibrillation enable drug screening in complex biological media. Improvement of long-range order can also provide structural guidance for the design of materials with high optical asymmetry.

Comparative statement analysis of span structures with a reinforced concrete and orthotropic plate under the exposure of solar radiation

Carried out a comparative analysis especially the exposure to solar radiation on the stress-strain state (SSS) of span structures with orthotropic slabs of reinforced concrete. Determine the character limit of the temperature distribution in the elements of the two types of spans according to the results of field measurements. Conducted calculation of Stress-Strain State on specific cases of solar radiation with the use of the developed finite element (FE) models of two types of span structures in the platform LIRA SAPR. The results of SSS features obtained for a steel-reinforced concrete superstructure and a metal superstructure with an orthotropic slab are compared. It is shown that the uneven daytime change in the temperature field under the influence of solar radiation has a significantly different nature of effect on the stress-strain state of elements of metal and steel-reinforced concrete span structures.

Investigation of heat release in metals under uniaxial stress state as a parameter of fatigue damage in metal bridges

The purpose of the issue is to study the process of heat release in metals under a symmetric loading cycle under conditions of uniaxial stress in order to assess the development of fatigue damage in the elements of metal superstructures of railroad and highway bridges. The author considered bending and axial loads of specimens with and without artificial concentrators. During the experiments, the samples were covered with matte paint, which ensured an emission coefficient of 0.95. For simultaneous fixation of thermal radiation on the upper and lower surfaces of the slots, mirrors were used. To eliminate interference from thermal radiation from surrounding objects, a fabric screen was installed between these objects and samples. As a result of experimental work, the author found that in all samples, regardless of their configuration and loading conditions, fatigue failure (the appearance of visible cracks) was preceded by a sharp increase in surface temperature at the same stress level, which the author called critical. The author during the study revealed that the magnitude of the critical stresses for the tested samples under uniaxial stress state and symmetric loading cycle does not depend on the number of concentrators, their sizes and location, but depends on the self-heating temperature and the type of deformation. Thus, the critical stress can be considered a characteristic of the material. The author also noted that at stresses greater than critical, an almost linear dependence of the temperature change on the total value of the stress increment is observed. Summarizing the noted properties of critical stresses, it can be argued that such stresses can be used to assess the development of fatigue damage when assessing the technical condition of a structure during bridge inspections. The work was performed as part of a dissertation research with the support of a grant from Russian Railways for the development of scientific and pedagogical schools.

Green fabrication of 2D platinum superstructures and their high catalytic activity for mitigation of organic pollutants

We report a simple eco-friendly green synthesis of self-assembled (SA) Pt nanoparticles, forming 2D sub-micrometric structures, from Coffea Arabica seed (CAS) extract. Small (˜2 nm) spherical Pt nanoparticles organized in the form of square/rectangular shaped 2D superstructures, have been utilized as efficient reusable catalysts for the reduction of industrial pollutants such as 4-nitrophenol (4-NP), methylene blue (MB) and their mixtures in aqueous medium (as well as in adsorbed state), with the activity parameters 0.75, 0.68 and 0.94 s−1 mg−1, respectively. The green process utilized for the fabrication of platinum superstructures in the present work could be extended for the fabrication of other metallic superstructures for efficient reusable catalytic reduction of organic contaminants.

Satellite surveillance of fishing vessel activity in the Ascension Island Exclusive Economic Zone and Marine Protected Area

Designation of large expanses of the ocean as Marine Protected Area (MPA) is increasingly advocated and realised. The effectiveness of such MPAs, however, requires improvements to vessel monitoring and enforcement capability. In 2014 commercial fishing was excluded from the Ascension Island Exclusive Economic Zone (EEZ). In 2015, through updated regulations, a licenced fishery re-opened in the northern half of the EEZ while the southern half remained closed. To assess compliance with these closures and regulations, several promising satellite technologies (Satellite Automatic Identification System (S-AIS), Synthetic Aperture Radar (SAR), Vessel Monitoring System (VMS) of two vessels), were trialled alongside at-sea patrols. Use of SAR enabled assessment of ‘dark’ (non-AIS transmitting) vessels, the scope of whose activities are hardest to gauge. The high level of compliance with regulations observed, suggests the MPA may prove effective, yet a need for vigilance remains. Vessels aggregate near the EEZ border and a quarter of vessels tracked across three years exhibited S-AIS transmission gaps and present a heightened compliance risk. Use of remote, rather than local, expertise and infrastructure provide a blue-print and economies of scale for replicating monitoring across similarly sized MPAs; particularly for large (>~ 25 m) vessels with metallic superstructures conducive to SAR detection. Funding ongoing monitoring in Ascension is challenged by current levels of license uptake, which provides insufficient offsetting revenue. Satellite-derived intelligence, can be used to set risk thresholds and trigger detailed investigations. Planning long-term monitoring must, however, incorporate adequate resources for follow-up, through patrols and correspondence with flag-states and fisheries management organisations.

Два пешеходных моста через Москву-реку. До и после

В статье приведены материалы по созданию двух крытых пешеходных мостов через реку Москву и освоению их при­брежных территорий; приводятся сведения об их иннова­ционном перемещении на новые створы. Оба моста были построены в 1905-1907годах в составе Московской кольцевой железной дороги; пешеход-ные мосты созданы на их основе. Как и прототипы, они заняли симметричное положение от­носительно оси «Кремль - Воробьёвы Горы» и излучины реки.
 Показаны различные подходы к реновации исторических объектов, освещаются некоторые концептуальные положения по проблемам соотношения старого и нового. Для Андреев­ского моста со старого створа были перемещены металличе­ское пролётное строение и исторический гранит береговых устоев. В архитектурное решение моста у Киевского вокзала включён только один исторический стальной арочный про­лёт, ставший основой композиции и уникальным экспонатом в интерьере нового крытого общественного пространства.
 Рассматриваются вопросы взаимодействия создаваемых объектов, окружающих ситуаций и формирования прилегаю­щих территорий. Новая крупная городская эспланада между Ленинским и Комсомольским проспектами в створе Андреев­ского моста связала районы Якиманки и Хамовников, а новая пониженная пешеходная набережная с причалом - ротонду архитектора М. Казакова и низкую набережную архитекора А. Власова. Другой мост связал районы Плющихи и Доро­гомилова; благоустроена площадь перед вокзалом, создан ансамбль фонтана «Похищение Европы».
 Новые мосты стали основой формирования городского пешеходного маршрута «Нескучный сад - Москва-Сити».
 За проектирование и архитектуру новых пешеходных мо­стов авторские коллективы удостоены премий Москвы и «Хру­стальный Дедал». Статью иллюстрируют авторские рисунки.

Assessment of two different Splinting materials on the immediate functional loading of Implants placed in mandibular unilateral free end saddle cases

Background: The class II Kennedy mandibular removable partial denture has many problemsas the different nature of support as well as crossing the arch for stabilization. The Target of thiswork was to evaluate the changes that occurs in the supporting structures of the implantsplaced in class II Kennedy cases as a result of two different types of splinting materials.Materials and Methods: Thirty implants were placed in ten patients with unmodifiedmandibular Kennedy Class II. For each patient, three implants were placed at the premolar/molarmandibular region. All the implants were immediately loaded following an Immediate FunctionalLoading Protocol. Patients were divided into two equal groups; Group A: received superstructuresthat were splinted with acrylic resin while Group B; received superstructures that were splintedwith metal. Radiographic evaluation using dental CT was carried out at intervals of 0, 6, 12 and24 months after implant surgery.Results: The results comprised the assessment of the bone height changes surrounding thethree implants placed unilaterally in the posterior mandibular areas of ten patients as a result of twodifferent splinting materials; the acrylic resin and the chrome cobalt metal alloy. Statistical analysisshowed that there was a statistically significant difference in the mean bone height values along thewhole study period between both groups (P ≤ 0.05) where there was more favorable bone heightvalues and hard tissue reaction in Group B (metal splinting) than Group A (Acrylic splinting).Conclusion: Within the limitation of this study, it can be concluded that the rigid splintingand immobilization of immediately loaded implants by metallic superstructures reduced thetransmission of micro-motion to the implant bodies and improved peri-implant bone reaction incomparison with the use of the less rigid acrylic resin material.

Electrochemical and Chemical Synthesis of Platinum Hierarchical Nanostructures Using Bicontinuous Microemulsions

Fabrication of hierarchical noble metal nanostructures is of interest due to the unique structural arrangement of nanoscale building blocks: nanocrystals or nanoparticles, composition and size are important in taking the physical and chemical usefulness of metal nanomaterials to a macroscopic scale. Various methods have been employed in achieving nanostructures of unique morphological arrangement. Amongst which are chemical and electrochemical reduction, or electrodeposition. In this research, platinum hierarchical nanostructures (PtHNs) were prepared using bicontinuous microemulsion (BC-ME) as soft templates. The PtHNs were synthesized using electrodeposition method as well as chemical reduction method. PtHNs was electrodeposited on Au macroelectrode from the bicontinuous microemulsion as well as from aqueous solution of chloroplatinic acid. Linear sweep voltammetry and chronopotentiometry was employed to achieve the deposition of Pt0 from the aqueous and bicontinuous platinum microemulsion electrolytic media. In the chemical method, sodium borohydride was used to reduce the hexachloroplatinic ions present in the bicontinuous microemulsion to platinum nanomaterial. In using bicontinuous microemulsions as a soft templates, the channels serve as continuous vessels for the converging growth of structures, which are dimensionally restricted by the diameter of the channels. PtHNs were characterized by SEM, EDX, TEM, XRD and cyclic voltammetry. The SEM images obtained, showed that the structure was unique, hierarchical with a regular morphology. From the SEM images, it was observed that the chemically synthesized PtHNs, were made up of interconnected spheres and self-assembled nanoneedles forming a nanocoral shape. The PtHNs XRD patterns confirm the polycrystalline nature of the platinum nanomaterials. Cyclic voltammetry (CV) of PtHNs synthesized through chemical reduction and electrodeposition method was conducted in degassed 0.5 M H2SO4. CV measurements (current voltage curve) essentially provide information about the electrochemical reactions that occurs on a working electrode surface. Electrochemical active surface area (ECSA) values of 35.1 m2/g and 20.9 m2/g were recorded for PtHNs synthesized by chemical reduction of 2% and 4% water soluble Pt precursor respectively. The highest ECSA value of 35.1 m2/g recorded from the PtHNs is higher than Pt dendritic tubes (23.3 m2/g) reported by Zhang et al. [1]. This clearly shows that the catalytic ability of the nanostructures synthesized in this work are highly desirable. The electrochemical surface area (ECSA) of 14.6 m2/g was recorded for the PtHNs electrodeposited on Au macroelectrode from aqueous Pt electrolyte while 12.2 m2/g was obtained when bicontinuous microemulsion of Pt was used as the platinum electrodeposition media. The PtHNs synthesized by the chemical method exhibited larger surface area than the platinum nanomaterial synthesized by electrodeposition. Broadly, this report presents a novel study of different synthetic methods for obtaining platinum nanostructures demonstrating the “template effect” of bicontinuous microemulsions towards the synthesis of metallic superstructures. Reference [1] Zhang, G., Sun, S., Cai, M., Zhang, Y., Li, R., and Sun, X., 2013, Porous dendritic platinum nanotubes with extremely high activity and stability for oxygen reduction reaction: Sci. Rep., 3, 1526. Figure 1

The actual operation assessment of the railway bridge superstructure using a mobile monitoring system

Deviations in the operation of the operated bridge structures on the railway are detected when damage occurs. At the same time, early detection and prognosis of damage progress can be obtained using monitoring systems. The article presents the methods and technologies for the use of mobile monitoring systems for assessing the actual operation of the metal superstructure of the railway bridge with the main driving trusses. The hardware of the measuring complex is considered, the main measuring instrument is the glued electrical strain gauges. The monitoring system kept a continuous record of sensor readings for 28 days. To process the data received by the monitoring system, specialized software has been developed that systematizes the incoming information. Analysis of the actual supertructure operation is carried out by finding the relationship of stresses in the various elements of the superstructure, arising under the same load. This approach allowed us to exclude the factor of unknown intensity of the temporary load. The results of monitoring the work of the superstructure are given. In total, over 680 train passage records were analyzed, which allowed for a statistical description of the data. The theoretical values of the relationship of stresses in the elements of the superstructure are determined using the apparatus of the influence lines obtained by a numerical method. The conclusions are made about the distribution of deformations of the superstructure under temporary load and about the degree of compliance with theoretical calculations. The construction factors and the values of their statistical scatter are determined, the actual dynamic factors are statistically calculated. The construction factors calculated from the stress ratios lie in the range of 0.8-1.116. Dynamic factors are within 1.13 and do not exceed the rated values.

Corrosion Behavior of Two cp Titanium Dental Implants Connected by Cobalt Chromium Metal Superstructure in Artificial Saliva and the Influence of Immersion Time

Corrosion Behavior of Two cp Titanium Dental Implants Connected by Cobalt Chromium Metal Superstructure in Artificial Saliva and the Influence of Immersion Time