Main Ribs Research Articles

МЕТОД ПРОЕКТУВАННЯ ТА ПАРАМЕТРИЧНОГО МОДЕЛЮВАННЯ СИЛОВОЇ НЕРВЮРИ КРИЛА ЛІТАКА ТРАНСПОРТНОЇ КАТЕГОРІЇ

The creation of any structural element begins with the design of basic geometric parameters. In the article, the method of designing and determining the main elements of the structure of the main ribs of the wing with conditions of static strength were reviewed, and a method of three-dimensional parametric modeling was developed. The rib is one of the most important elements of the wing, which act significant flight loads, and the main ribs additionally act concentrated forces. The article analyzed the design features of the rib design of the wing of the transport category aircraft. An analysis of the current loads on the main rib was performed, shear and bending diagrams were determined. During realize high-lift devices, the aerodynamic flow of the wing changes significantly, which leads to a change in the stress-strain state of the wing. This relates not only to the increase in lift due to a change in the curvature of the wing and an increase in the wing area, but also due to a change in the position of the center of pressure relative to the chord of the wing. Therefore, to determine the loads, the aerodynamic characteristics, obtained by the numerical method in the ANSYS program, were used. In order to remain competitive, the aviation company needs to ensure the high quality of the manufactured equipment, its quick modernization and modification or change of the model series. The use of CAD/CAM/CAE/PLM systems at all stages of the life cycle of aviation parts, including the design and production stages, can significantly improve the quality of the created parts and reduce the cost of performing work related to design and production, while maintaining high rates of work. The method of three-dimensional parametric modeling of the main machined wing rib was developed using the Siemens NX computer integrated system, which allows to significantly reduce the stage of modeling typical elements of the aircraft airframe structure using the created three-dimensional parametric model of a typical structural element

Mojiangia oreophila (Crepidinae, Cichorieae, Asteraceae), a new species and genus from Mojiang County, SW Yunnan, China, and putative successor of the maternal Faberia ancestor

A single small population of chasmophytic plants is described as Mojiangiaoreophila, a monotypic genus in the subtribe Crepidinae, characterised by a unique combination of morphological features, in particular densely long-papillose homomorphic achenes with five main ribs each accompanied by two secondary ribs, coarse brownish pappus bristles, moderately many-flowered capitula, a small involucre with numerous outer phyllaries, perennial rosette herb growth and brown-woolly caudex and leaf axils. Molecular phylogenetic analysis detected that in the nrITS phylogeny M. oreophila forms a clade of its own in the Crepidinae; in the plastid DNA phylogeny it is nested in the clade formed by the hybridogenous genus Faberia, the maternal ancestor of which comes from the Crepidinae and the paternal ancestor from the Lactucinae, where Faberia is placed in nrITS phylogenies. M. oreophila shares several morphological features with Faberia and also shares the expected chromosome number of 2n = 16 with its hitherto unknown maternal ancestor. M. oreophila may therefore be a successor of the maternal ancestor of Faberia. Alternatively, cytonuclear discordance is to be assumed in Mojiangia, caused by chloroplast capture as a result of hybridisation and introgression with Faberia.

Detection of initial strain of main ribs of concrete beam (or slab) by bending moment increment method

In the inspection and identification of engineering structures, it is often necessary to understand the force state of the main ribs of the components. Based on the structural performance test, the relationship between the bending moment of the concrete beam (or slab) in the elastic phase and the plastic phase and the strain of the main rib is analyzed. The initial moment of the main beam of the concrete beam (or slab) is proposed by the bending moment increment method. By adding a small amount of bending moment and measuring the strain increment of the main rib, the initial strain of the main rib of the flexural member is estimated to better understand the structural performance of the member. During the bending moment increment detection process, the increase in bending moment is small and does not adversely affect the concrete structure.

Stability of cable-supported spherical reticulated shell with tension members

The suspendome has been widely employed in large-span space structures in recent years, and it has stronger structural stiffness and higher load-carrying capacity than single-layer spherical reticulated shell. In general, it is negligible for enhancement of load-carrying capacity to integrate cables and struts into the inner ring of reticulated shell. Based on the suspendome structure, a new hybrid space structure system, namely, cable-supported reticulated shell with tension member, is proposed in this study. To elucidate and verify its feasibility, the buckling mode and buckling form are obtained by the eigenvalue buckling analysis and nonlinear buckling analysis using ANSYS package, respectively. Furthermore, to determine the optimal structural form, this article investigates the effect of the main ribbed strut length, the initial geometric imperfection, asymmetric load, pretension in cables, and the material nonlinearity on its stability. The result shows that the proposed new structural system is of high load-carrying capacity. Tension member integrated to cable-supported reticulated shell can effectively improve the overall stiffness and greatly reduce the deformation of spherical reticulated shell. The plastic failure shape occurs with the similar pattern. The instable region mainly occurs on the main ribs with tension members, and each main rib only has one local failure dimple. The load-carrying capacity is remarkably affected by the asymmetric load, the initial geometric imperfection, and material nonlinearity. Based on the parametric analyses, Type C is the optimal choice, that is, appending cables and struts to the outermost ring of single-layer spherical reticulated shell, and arranging out-of-plane tension members under the four main ribs.

Procedures Used for Strengthening Pavia’s Cathedral, Italy

This paper deals with the two kinds of pathologies of Pavia’s Cathedral discussed in a previous paper, and the intervention techniques implemented for its strengthening. Their conception and some details of the methods are described here. For the retrofitting of the pillars (first pathology), an innovative procedure was used, based on the horizontal precompression of the infill and on the partial transfer of the load from the marble lining to the infill, while for the cracked dome (second pathology), the increase in strength was achieved by a simple application of carbon-fibre strips to the main ribs.

The Cast-Iron Bridge at Sunderland

Sunderland Bridge, when built, was the longest iron arch in the world. Discussions about building it with stone had been held in the 1780s but the idea of an iron structure took hold in 1791 and as such it was finally opened in 1796. Severe deterioration soon occurred and only drastic action in 1805 saved it from collapse. Thereafter it survived until 1853 when it was largely rebuilt although the main ribs remained in situ. Total replacement took place in the 1920s, the present bridge being opened in 1929.

Análise de cargas acidentais em pavimentos de garagem

O trabalho tem como foco a análise das cargas acidentais utilizadas para pavimentos de garagem, considerando as recomendações de normas nacionais e internacionais para a definição do valor das cargas a serem aplicadas nas lajes nervuradas. A norma brasileira NBR 6120/1980 [1], que trata do assunto, não especifica nada em relação a cargas concentradas, enquanto normas internacionais como Euro Code [2] e IBC [3], recomendam considerar cargas distribuídas e concentradas. Atualmente, as lajes nervuradas são utilizadas amplamente em pavimentos de garagem. Neste contexto, considerando os padrões de veículos mais utilizados no país, será que os valores de cargas distribuídas das normas são adequados para o dimensionamento das lajes nervuradas? Ou é necessário fazer uma correção destas cargas para levar em consideração as cargas concentradas da ordem de 8,5 kN por pneu correspondente a um veículo utilitário. O objetivo deste trabalho é procurar as respostas para estas duas perguntas através de uma análise paramétrica envolvendo os principais parâmetros de uma laje nervurada, que são: a relação (lambda) entre os lados, a distância entre as nervuras principais e o esquema de apoio da laje (uni ou bidirecional). De uma forma geral o conjunto das simulações mostra que as cargas recomendadas pelas normas citadas precisariam de correção quando utilizadas em pavimento de garagem para reproduzir o efeito das cargas concentradas das rodas de veículos tipo utilitário.

Influence of some chosen morphactins on tissue formation in sunflower (Helianthus annuus L.) leaves

The influence of two morphactins (IT 3233 and IT 3456) on the formation of tissues in sunflower leaves was investigated. The leaves were usually smaller, they had plicate laminae and rolled up edges. The different influence of morphactins in dependence on the position of the leaves on the stem and on the kind of tissues was confirmed. Leaves growing from the first node had the thickest laminae, main ribs and the longest cells of palisade parenchyma. The values contrasted with those in the leaves from the third node. An increase of the number of epidermis cells and stomata in leaves from the first and second node and a decrease in those from the third node were observed. Additional layers (1-2) of palisade parenchyma in leaves of the second and third node were formed. Mesophyll was very compact. Xylem consisted of a greater number of elements, arranged compactly and of much lower diameter.

Utility of Digital Radiography for the Screening of Pneumoconiosis as Compared to Analog Radiography

The purpose of this study was to compare digital radiography (DR) and analog radiography (AR) for the screening of pneumoconiosis with respect to radiation dose, image quality, and pneumoconiosis classification. DR was performed on 50 subjects who were enrolled for an examination of pneumoconiosis (Digital Diagnost™, Philips, Netherlands), and AR (MXO-15B, Toshiba, Japan) was performed the same day after the study was approved by the Institutional Review Board and written informed consent was obtained from all subjects. Entrance surface doses (ESDs) of DR and AR were measured using a glass dosimeter attached to a Rando human phantom (Alderson Co., U.S.) under exposure conditions commonly used in clinical practice in Korea. Visibilities on all images were evaluated using a 5-point scale by four chest radiologists using a modified form of the European Chest Guidelines (EUR 16260). All the images were classified using the ILO's guidelines by referencing standard analog radiographs. ESDs of DR were significantly lower than those of AR (0.15 mGy vs. 0.21 mGy, p < 0.05). All anatomic structures were significantly more visible by DR images (p < 0.0001), especially the left main bronchus, ribs, and thoracic spine. Body mass index did not correlate with anatomic structure visibility by DR (r = -0.029, p = 0.842) or AR images (r = -0.076, p = 0.602). Overall intra- and inter-reader agreements for DR images were significantly higher than for AR images. DR offers improved image quality with a significant reduction of up to 23.6% in radiation dose and more accurate pneumoconiosis classification than AR.

The Barremian heteromorph ammonite Dissimilites from northern Italy: taxonomy and implications

A new acrioceratid ammonite, Dissimilites intermedius sp. nov., from the Barremian (Lower Cretaceous) of the Puez area (Dolomites, northern Italy) is described. Dissimilites intermedius sp. nov. is an intermediate form between D. dissimilis and D. trinodosum. The new species combines the ribbing style of D. dissimilis (bifurcating with intercalating single ribs) with the tuberculation style of D. trinodosum (trituberculation on entire shell). The shallow-helical spire, entirely comprising single ribs intercalated by trituberculated main ribs, is similar to the one of the assumed ancestor Acrioceras, whereas the increasing curvation of the younger forms resembles similar patterns observed in the descendant Toxoceratoides. These characters support the hypothesis of a direct evolutionary lineage from Acrioceras via Dissimilites to Toxoceratoides. D. intermedius sp. nov. ranges from the upper Lower Barremian (Moutoniceras moutonianum Zone) to the lower Upper Barremian (Toxancyloceras vandenheckii Zone). The n...

Seismic Behaviors of an Upper Deck Type Steel Arch Bridge

The static and dynamic behavior of an upper deck type steel arch bridge was demonstrated. During the static analysis, both material and geometric nonlinear was considered based on finite element (FE) method. In-plane fault displacement case and out-off-plane fault displacement case were compared. During dynamic analysis, the model was modified and simplified firstly, and then the natural modals and the characteristics of the mode shape were analyzed. Both the in-plane seismic input case and out-off-plane seismic input case were analyzed. The different yielding process of members including main ribs, chord and columns were represented, and the possible damaged parts of the bridge were analyzed either.

The buckling characteristics of some integrally formed bead stiffened composite panels

Composite panel stability can easily be improved by using vertical male beads. In this paper, new methods of stabilizing techniques used for the panels, webs and ribs of composite structures are studied. A parametric study is performed to assess the effects of important design considerations such as, bead length, number of beads, bead radius, bead depth and bead spacing on the initial buckling load of the panels. The results show that, there is an optimum bead spacing for each panel containing more than one bead which can be estimated using a simple equation. Integration of vertical beads with a length of less than 0.5 times the panel's length has no significant effect on the buckling load. There are no significant changes on the buckling loads of the beaded panels with bead depths greater than 0.6 times the bead radius. In this investigation, the instability of the nose and main ribs of a light airplane wing structure made of woven E-glass material and stiffened by P.V.C foam core and vertical male beads are also studied using experimental methods. The experimental results show that we can easily improve the buckling capability of the panels and webs by using vertical male beads instead of sandwiched construction. It is estimated that this would cause a weight reduction of about 50% and a manufacturing time reduction of about 50%.

The Karsteniceras level: Dysoxic ammonoid beds within the Early Cretaceous (Barremian, Northern Calcareous Alps, Austria)

An Early Cretaceous mass-occurrence of ammonites in the Ternberg Nappe of the Northern Calcareous Alps (Upper Austria) is described for the first time. The mass-occurrence (section KB1-B=Klausrieglerbach 1, section B) dominated by Karsteniceras ternbergense Lukeneder is of Early Barremian age (Moutoniceras moutonianum Zone). The Karsteniceras mass-occurrence comprises eight different genera, each apparently represented by a single species, of which four are identified to species level. About 300 specimens of K. ternbergense between 5 and 37 mm in diameter were investigated. Two groups showing thick main ribs but different maximum size are distinguishable. The latter parameters are suggested to reflect sexual dimorphism within K. ternbergense, a condition that is most probably applicable to the whole leptoceratoid group. The geochemical results indicate that the Karsteniceras mass-occurrence within the described Lower Cretaceous succession was deposited under intermittent oxygen-depleted conditions associated with stable, salinity-stratified water masses. The rhythmicity of laminated black-marly lime-stone layers and light-grey bioturbated, organic-poor lime-stones suggests that the oxic and dysoxic conditions underwent highly dynamic changes. The deposition of the limestones in this interval occurred in an unstable environment and was controlled by short- and long-term fluctuations in oxygen levels. Karsteniceras inhabited areas of stagnant water with low dissolved oxygen; it showed peak abundance during times of oxygen depletion, which partially hindered other invertebrates from settling in such environments. The autochthonous Karsteniceras mass-occurrence can be assigned to the deposition-type of ‘Konservat Lagerstatte’, which is indicated by the preservation of phosphatic siphuncle structures and proved by the in situ preservation of aptychi within Karsteniceras ternbergense. Based on lithological and geochemical analysis combined with in vestigations of trace fossils, microfossils and macrofossils, an invasion of an opportunistic (r-strategist) Karsteniceras biocoenosis during nonfavorable conditions over the sea bed during the Lower Barremian is proposed for the KB1-B section.

New species of Silurian acanthodians from the Mackenzie Mountains, Canada

Two new acanthodian taxa are described. The ischnacanthid Xylacanthus kenstewarti is based on large, dentigerous jaws, and Granulacanthus joenelsoni is based on isolated spines. The isolated remains of these species are similar in that they both possess pustulose denticles or tubercles, either on the mesial ridge (X. kenstewarti) or on the fin spines (G. joenelsoni). Jaws of X. kenstewarti are similar in size to those of Xylacanthus minutus, Ischnacanthus kingi, and I. wickhami and smaller than those of X. grandis. The jaws of X. kenstewarti are most similar to those of X. minutus, but are distinguished from this and other ischnacanthid species by a tapering patch of pustulose denticles that is widest midway along the jaw, mesial denticles that are simple blisterlike structures, the monocuspid, striated primary teeth that are subcircular in cross section, and a posterodorsal process that is enlarged. The spines of G. joenelsoni have distinctive tubercular ornamentation. Tubercles, or nodular ornaments on fin spines, are characteristic of primitive acanthodians, but the slender shape of the spines, the low number of spine ribs, and the fine striations posterior to the main ribs of each spine suggest that G. joenelsoni is a relatively advanced acanthodian. Xylacanthus kenstewarti and G. joenelsoni are from the Silurian (Wenlock or Ludlow) of the southern Mackenzie Mountains. Xylacanthus kenstewarti represents the earliest representative of the genus, the earliest unequivocal remains of a gnathostome from the Mackenzie Mountains, and extends the known geographical range of the genus from the Mackenzie Mountains east to Spitsbergen.

Durability design criteria for bituminous pavements on orthotropic steel bridge decks

Many inspections of the pavements of orthotropic steel bridge decks show longitudinal cracks above the connections of the deck plate to the main girders and ribs. By using a simplified model for analysing the behaviour of the pavement and comparing the theoretical results with damage records, the ultimate resistance of the pavement is defined, and minimum stiffness requirements for orthotropic decks are derived. These serviceability limit states have been included in a recent draft of the German steel road–bridge code DIN 18809.Theoretical studies of the material behaviour lead to proposals for the minimum strength requirements for bituminous pavements, which may be used in conjunction with the results of material tests. This procedure will improve the strength design of bituminous bridge pavements. Key words: bitumen, bridge decks, composite structures, design criteria, durability, limit design method, orthotropic plates, pavements, serviceability limits, specifications, steel.

Lateral Load Effect on Steel Arch Bridge Design

Design criteria for lateral load effect of two‐hinged, parabolic, steel arch bridge structures are presented on the basis of the ultimate limit state design concept. The arch structures are composed of two main ribs connected by a lateral bracing system. The load combination that is considered consists of vertical loading and practical lateral loading to which bridge structures are actually subjected. Based on results of their load carrying capacity analyzed by three‐dimensional finite element method, ways of incorporating practical lateral loading effects in the ultimate strength designing of steel arch bridge structures are presented. The required out‐of‐plane rigidities of steel arch bridge structures are also proposed.

Lateral Load Effect on Load Carrying Capacity of Steel Arch Bridge Structures

Several numerical results for the load carrying capacity of two hinged, parabolic, steel arch bridge structures—determined by an accurate finite element approach—are presented. The arch structures are composed of two main ribs connected by a lateral bracing system. The load combination that is considered consists of vertical loading and practical lateral loading to which bridge structures are actually subjected. From the numerical results, the influence of several parameters on the strength of arch structures is discussed. It is concluded that the load carrying capacity of arch bridge structures with conventional out-of-plane rigidities, under vertical and practical lateral loading, may be determined by a simpler, quasi-planar structural analysis.

Leaf development in Begonia hispida var. cucullifera with special reference to vascular organization

The leaf is initiated by periclinal divisions in the second cell layer of the apex. Early in development, it assumes an asymmetrical shape as a result of the non-median position of the apical meristematic region that forms the leaf tip. The other main lobes of the leaf are formed by two additional regions of growth to the side of the tip. In the second plastochron, primordia are initiated on the upper surface of the main ribs of the leaf and these often develop into large, leaf-like appendages. During the third plastochron, the leaf becomes covered by a dense layer of trichomes. Vascular development is well correlated with regions of growth. The median procambial strand extends diagonally into the skewed apical growth region and another strand branches from this and develops on the other side. Lateral procambial strands usually form in an abaxial to adaxial sequence in the petiole: one strand of the first pair to develop forms part of the median rib and the other forms a third main rib on the opposite side. After the initiation of primordia on the leaf surface, a 'ventral system' of procambia is developed supplying mainly the ventral rib surface and consequently the epiphyllous appendages. This consists of branches from the adaxial-most peripheral bundles in the petiole as well as a bundle in the centre. The vascular anatomy of the stem and nodal region is also described in relation to that of the leaf.

OUT-OF-PLANE BUCKLING OF SOLID RIB ARCHES BRACED WITH TRANSVERSE BARS

The out-of-plane buckling of a circular arch is studied. The arch is composed of two main ribs braced with transverse bars and is subjected to uniformly distributed radial forces (see Fig. 1). The analysis is carried out by means of transfer matrix method and both the field matrix of arched rod and point matrix are presented. Attention is given to the influences of the flexural rigidity, the number and the location of bracing bars on the buckling strength of arches. Buckling coefficients for various types of arch are calculated by trial and error method. Useful suggestions about the bracing method are obtained from the results of computations. The theoretical analysis is followed by model tests in order to verify the results of computation.

The Plane and Tractor Used by the British Graham Land Expedition

Only one aeroplane could be taken by the expedition and this necessarily had to be a single-engined machine, as there were no twin-engined aeroplanes at the price which the expedition could afford to pay. As a result great care had to be taken to choose a machine which was equally good as a seaplane and as a skiplane, with quickly interchangeable undercarriages, and which would combine as many of the most essential qualities as possible. The first essential was wooden construction. Many people, apparently qualified to give an opinion, will say that wooden construction is not suitable for service in cold climates, but I have found it extremely good during eighteen months' hard service in Greenland, and again after two and a half years in the Antarctic in much more severe conditions. The chief advantage on an expedition is the ease with which even major repairs can be carried out. It is not necessary to take a comprehensive supply of airframe spares as these can all be cut straight from a length of suitable timber, and even main and tail plane ribs can be constructed with a little patience. The wooden construction appears to be every bit as robust as metal and, of course, cannot corrode.