Articles de revues : « Lateral instability of beams »

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KRAHL, P. A., M. C. V. LIMA et M. K. EL DEBS. « Recommendations for verifying lateral stability of precast beams in transitory phases ». Revista IBRACON de Estruturas e Materiais 8, n^o 6 (décembre 2015) : 763–74. http://dx.doi.org/10.1590/s1983-41952015000600003.

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Abstract This paper presents recommendations for security check of precast beams in transitory phases, compare results of parametric analyzes with national and international code recommendations and confront the formulations used for the calculation of critical load of lateral instability. In transport and lifting phases, precast beams are susceptible to loss lateral stability because the established supports provides little restriction to the element rotate on its principal axis and move laterally. To recommend limits of slenderness, parametric analysis are performed using formulations based on bifurcacional instability, including eigenvalue problems with the finite element method. The results show that the safety limits for I beams and rectangular beams are different. For the analyzed cases and with reference to beam slenderness equation used by fib Model Code [13], the limit determined for rectangular beams would be 85 and for I beams 53, which could be taken as 50, as recommended by the code. Within the analyzed cases of I beams, only the fib Model Code [13] recommendation attend the slenderness limit for transitory phases.

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Law, K. H., et L. Gardner. « Lateral instability of elliptical hollow section beams ». Engineering Structures 37 (avril 2012) : 152–66. http://dx.doi.org/10.1016/j.engstruct.2011.12.008.

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Roberts, T. M., et M. Benchiha. « Lateral instability of monosymmetric beams with initial curvature ». Thin-Walled Structures 5, n^o 2 (janvier 1987) : 111–23. http://dx.doi.org/10.1016/0263-8231(87)90003-6.

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Li, Yu Mei. « The Out-of-Plane Instability of a Bending Beam with Multiple Loads ». Advanced Materials Research 211-212 (février 2011) : 930–34. http://dx.doi.org/10.4028/www.scientific.net/amr.211-212.930.

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This paper presents the characteristic equation of out-of-plane instability when a bending beam, which is composed of two beams, is under lateral force and vertical force. It clarifies a method which can calculate the out-of-plane instability load of a structural component with main jib and counterbrace.

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Nakashima, Masayoshi, Iori Kanao et Dawei Liu. « Lateral Instability and Lateral Bracing of Steel Beams Subjected to Cyclic Loading ». Journal of Structural Engineering 128, n^o 10 (octobre 2002) : 1308–16. http://dx.doi.org/10.1061/(asce)0733-9445(2002)128:10(1308).

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CARDOSO, M. T. S. A., et M. C. V. LIMA. « Wind load effect on the lateral instability of precast beams on elastomeric bearing supports ». Revista IBRACON de Estruturas e Materiais 13, n^o 3 (juin 2020) : 593–602. http://dx.doi.org/10.1590/s1983-41952020000300009.

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Abstract The behavior of slender precast beams related to lateral stability in the transitional and in service phases is worrying. The presence of geometric imperfections aggravates and makes the problems of instability more susceptible. The main objective of this work is to evaluate the behavior of concrete beams on elastomeric bearings and to analyze the influence of variables such as: concrete strength, wind load and bearing compression stiffness. For the numerical nonlinear analysis the software ANSYS based on the Finite Element Method was used. The analyses show that the influence of the strength of the concrete is significant in the lateral stability of the beam. The wind load represents a considerable decrease in the contact (lift off) between the beam and the bearing. Finally, the combination of these factors can result in a critical stress situation in the beam, and it is not possible to have equilibrium, causing its toppling.

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Gaith, Mohamed, et Sinan Müftü. « Lateral Vibration of Two Axially Translating Beams Interconnected by a Winkler Foundation ». Journal of Vibration and Acoustics 129, n^o 3 (13 septembre 2006) : 380–85. http://dx.doi.org/10.1115/1.2732353.

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Transverse vibration of two axially moving beams connected by a Winkler elastic foundation is analyzed analytically. The two beams are tensioned, translating axially with a common constant velocity, simply supported at their ends, and of different materials and geometry. The natural frequencies and associated mode shapes are obtained. The natural frequencies of the system are composed of two infinite sets describing in-phase and out-of-phase vibrations. In case the beams are identical, these modes become synchronous and asynchronous, respectively. Divergence instability occurs at a critical velocity and a critical tension; and, divergence and flutter instabilities coexist at postcritical speeds, and divergence instability takes place precritical tensions. The effects of the mass, flexural rigidity, and axial tension ratios of the two beams are presented.

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PIASSI, A. D., J. V. DIAS, A. F. G. CALENZANI et F. C. C. MENANDRO. « Lateral distortional buckling of cellular composite-beams ». Revista IBRACON de Estruturas e Materiais 11, n^o 2 (avril 2018) : 331–56. http://dx.doi.org/10.1590/s1983-41952018000200007.

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Abstract In the region of negative bending moments of continuous and semi-continuous steel and concrete composite beams, the inferior portion of the steel section is subjected to compression while the top flange is restricted by the slab, which may cause a global instability limit state know as lateral distortional buckling (LDB) characterized by a lateral displacement and rotation of the bottom flange with a distortion of the section’s web when it doesn’t have enough flexural rigidity. The ABNT NBR 8800:2008 provides an approximate procedure for the verification of this limit state, in which the resistant moment to LDB is obtained from the elastic critical moment in the negative moment region. One of the essential parameters for the evaluation of the critical moment is the composite beam’s rotational rigidity. This procedure is restricted only to to steel and concrete composite beams with sections that have plane webs. In this paper, an equation for the calculation of the rotational rigidity of cellular sections was developed in order to determine the LDB elastic critical moment. The formulation was verified by numerical analyses performed in ANSYS and its efficiency was confirmed. Finally, the procedure described in ABNT NBR 8800:2008 for the calculation of the critical LDB moment was expanded to composite beams with cellular sections in a numerical example with the appropriate modifications in geometric properties and rotational rigidity.

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Lee, Jong Han, et Ilker Kalkan. « Experimental and Analytical Investigation of Lateral-Torsional Buckling of RC Beams with Geometric Imperfections ». Applied Mechanics and Materials 479-480 (décembre 2013) : 1133–38. http://dx.doi.org/10.4028/www.scientific.net/amm.479-480.1133.

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The design of reinforced concrete beams has usually focused on the ultimate flexural capacity and disregarded the lateral stability of the beams. However, the development of high-strength concrete and the implementation of new construction techniques increase the use of longer and deeper concrete beams, which makes the lateral instability a primary concern of failure in concrete bridges. In particular, the lateral stability should be more taken into consideration in the construction and erection phases due to inadequate lateral supports. Thus, an experimental study was carried out to evaluate the lateral torsional buckling of reinforced concrete beams with initial geometric imperfections. The lateral flexural and torsional rigidity expressions, which could account for the flexural, torsional, and shrinkage cracking of concrete, the contribution of longitudinal and shear reinforcement, and the nonlinearity of materials, were proposed for rectangular reinforced concrete beams. Finally, this study proposed an analytical formula to estimate the buckling loads of initially imperfect reinforced concrete beams. The estimates of the study showed close agreement with the experimental values.

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Kucukler, Merih. « Lateral instability of steel beams in fire : Behaviour, numerical modelling and design ». Journal of Constructional Steel Research 170 (juillet 2020) : 106095. http://dx.doi.org/10.1016/j.jcsr.2020.106095.

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Dekker, N. W., et A. R. Kemp. « A simplified distortional buckling model for doubly symmetrical I-sections ». Canadian Journal of Civil Engineering 25, n^o 4 (1 août 1998) : 718–27. http://dx.doi.org/10.1139/l98-001.

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Lateral torsional instability of I-beams considers the relative displacement of the unstable compression flange to the stable tension flange. It is commonly assumed that little or no distortion takes place between the two flanges. In this paper, an approach is proposed whereby the section properties that control lateral torsional buckling are adjusted to allow for the influence of cross-section distortion, by the use of simple spring models representing the relative stiffness of the flanges and the web. The model is developed for elastic, inelastic, and plastic cases and compared with the results obtained from finite element models developed by other researchers. A method of quantifying the lateral distortional buckling resistance of I-beams is of particular importance in the hogging moment region of continuous composite beams; the ability of the proposed model to deal with this complex problem has been previously demonstrated by the authors. In this paper, the proposed model is used to illustrate the influence of distortional buckling on doubly symmetrical I-sections.Key words: lateral, distortional, I-beams, elastic, inelastic.

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KRAHL, P. A., R. CARRAZEDO et M. K. EL DEBS. « Rollover stability of precast concrete beams supported by elastomeric bearing pads ». Revista IBRACON de Estruturas e Materiais 10, n^o 6 (novembre 2017) : 1192–204. http://dx.doi.org/10.1590/s1983-41952017000600005.

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Abstract During construction of precast girder bridges, there is the concern on rollover instability of the beams when exclusively supported by elastomeric bearing pads. This type of failure has been the focus of recent research due several accidents reported. However, these studies have not considered the nonlinear behavior of elastomeric bearing pads and the lift-off effect. Therefore, this paper presents a parametric study with a finite element model calibrated with experimental results, reported in the literature, through a nonlinear geometrical analysis and considering that concrete behaves linearly. Besides, the experimental results are compared to simplified approaches which account the pad nonlinear behavior and the lift-off effect by utilizing its secant rotational stiffness. From the results, the difference between the instability load from nonlinear geometrical analysis and experimental results was 8.7 %, and the simplified eigenvalue solution and experimental was 11.4 %, which was the best fit compared to the other existing analytical models. From the parametrical analysis, the instability load was considerably decreased by varying the initial lateral deflection, the skewed pad rotation, top flange width and the span of the beam.

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Mascolo, Ida, Mariano Modano, Antimo Fiorillo, Marcello Fulgione, Vittorio Pasquino et Fernando Fraternali. « Experimental and Numerical Study on the Lateral-Torsional Buckling of Steel C-Beams with Variable Cross-Section ». Metals 8, n^o 11 (13 novembre 2018) : 941. http://dx.doi.org/10.3390/met8110941.

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Metallic thin-walled beams with continuously varying cross-sections loaded in compression are particularly sensitive to instability problems due to lateral-torsional buckling. Such a phenomenon depends on several parameters, including the cross-sectional properties along the entire length, material properties, load distribution, support, and restraint conditions. Due to the difficulty of obtaining analytic solutions for the problem under consideration, the present study takes a numerical approach based on a variational formulation of the lateral-torsional buckling problem of tapered C-beams. Numerical simulations are compared with experimental results on the buckling of a physical model of at thin-walled beam with uniformly varying cross-section, with the aim of assessing the accuracy of the proposed approach. The good agreement between numerical and experimental results and the reduced computational effort highlight that the proposed variational approach is a powerful tool, provided that the geometry of the structure and the boundary conditions are accurately modeled.

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Krahl, Pablo Augusto, Diego de Oliveira Martins, Ricardo Carrazedo, Irineu da Silva et Mounir Khalil El Debs. « Experimental and analytical studies on the lateral instability of UHPFRC beams lifted by cables ». Composite Structures 209 (février 2019) : 652–67. http://dx.doi.org/10.1016/j.compstruct.2018.11.002.

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REIS, L. C., P. A. KRAHL et M. C. V. LIMA. « Numerical analysis of the effective stiffness of elastomeric bearing pads under precast beams for the limit load of lateral instability ». Revista IBRACON de Estruturas e Materiais 13, n^o 1 (février 2020) : 95–119. http://dx.doi.org/10.1590/s1983-41952020000100008.

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Abstract Precast concrete girders on bearing pads are subjected to instability depending on several variables such as span length, initial imperfections and bearing pads behavior. On this paper, numerical models are developed in order to assess the instability limit loads and the rotational stiffnesses of the pads in many combinations of span length, cross section of the girder and lateral sweep. The lift off phenomenon is considered in each analysis by a bearing pad model composed by springs with compression only behavior, with good results in comparison with the experimental values of the technical literature. The increase in spans and initial imperfections causes a decrease in the rollover limit load. The lift off effect is aggravated as the lateral eccentricities increase. In the analyzed combinations, the reduction of the rotational stiffness is about 37% for the critical situation, which span length about 40 m and lateral sweep of L/300, with loss of contact between 50% and 60%.

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Wadee, M. Ahmer, et Leroy Gardner. « Cellular buckling from mode interaction in I-beams under uniform bending ». Proceedings of the Royal Society A : Mathematical, Physical and Engineering Sciences 468, n^o 2137 (21 septembre 2011) : 245–68. http://dx.doi.org/10.1098/rspa.2011.0400.

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Beams made from thin-walled elements, while very efficient in terms of the structural strength and stiffness to weight ratios, can be susceptible to highly complex instability phenomena. A nonlinear analytical formulation based on variational principles for the ubiquitous I-beam with thin flanges under uniform bending is presented. The resulting system of differential and integral equations are solved using numerical continuation techniques such that the response far into the post-buckling range can be portrayed. The interaction between global lateral-torsional buckling of the beam and local buckling of the flange plate is found to oblige the buckling deformation to localize initially at the beam midspan with subsequent cellular buckling (snaking) being predicted theoretically for the first time. Solutions from the model compare very favourably with a series of classic experiments and some newly conducted tests which also exhibit the predicted sequence of localized followed by cellular buckling.

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Plaut, R. H. « Lateral-torsional dynamic instability of uniform and double-tapered rectangular beams under harmonic shear deformation ». Engineering Structures 146 (septembre 2017) : 140–47. http://dx.doi.org/10.1016/j.engstruct.2017.05.043.

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Nethercot, D. A. « Discussion of “Lateral Instability of I‐Beams with Imperfections” by Hiroshi Yoshida and Kouji Maegawa (August, 1984) ». Journal of Structural Engineering 112, n^o 1 (janvier 1986) : 197–99. http://dx.doi.org/10.1061/(asce)0733-9445(1986)112:1(197).

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Yoshida, Hiroshi, et Kouji Maegawa. « Closure to “ Lateral Instability of I‐beams with Imperfections ” by Hiroshi Yoshida and Kouji Maegawa (August, 1984) ». Journal of Structural Engineering 112, n^o 1 (janvier 1986) : 199. http://dx.doi.org/10.1061/(asce)0733-9445(1986)112:1(199).

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Janbaz, S., K. Narooei, T. van Manen et A. A. Zadpoor. « Strain rate–dependent mechanical metamaterials ». Science Advances 6, n^o 25 (juin 2020) : eaba0616. http://dx.doi.org/10.1126/sciadv.aba0616.

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Mechanical metamaterials are usually designed to exhibit novel properties and functionalities that are rare or even unprecedented. What is common among most previous designs is the quasi-static nature of their mechanical behavior. Here, we introduce a previously unidentified class of strain rate-dependent mechanical metamaterials. The principal idea is to laterally attach two beams with very different levels of strain rate-dependencies to make them act as a single bi-beam. We use an analytical model and multiple computational models to explore the instability modes of such a bi-beam construct, demonstrating how different combinations of hyperelastic and viscoelastic properties of both beams, as well as purposefully introduced geometric imperfections, could be used to create robust and highly predictable strain rate-dependent behaviors of bi-beams. We then use the bi-beams to design and experimentally realize lattice structures with unique strain rate-dependent properties including switching between auxetic and conventional behaviors and negative viscoelasticity.

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Zhu, Jue, Shanguang Qian et Long-yuan Li. « Dynamic instability of laterally-restrained zed-purlin beams under uplift loading ». International Journal of Mechanical Sciences 131-132 (octobre 2017) : 408–13. http://dx.doi.org/10.1016/j.ijmecsci.2017.07.021.

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Maślak, Mariusz, Krzysztof Kuchta et Marcin Łukacz. « Bending resistance of steel beams with corrugated web under fully developed fire ». Budownictwo i Architektura 12, n^o 2 (11 juin 2013) : 229–36. http://dx.doi.org/10.35784/bud-arch.2136.

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More accurate design algorithm helpful in bending resistance evaluation of steel beams with corrugated web exposed to fully developed fire is presented and discussed in detail. The condition of fire resistance limit state is proposed to be determined by the interactive formula based on the consideration of biaxial bending in which the transverse out-of-plane bending phenomenon is the spatial effect of in-plane shear. Such an influence, usually neglected in formal models dealing with the persistent design situation, can become more significant under fire conditions, when the steel yield point decreases as a consequence of the flanges temperature growth. Dependence between the material temperature and the global instability factors is considered in the methodology proposed by the authors, especially with relation to the assessment of the adequate values of lateral – torsional buckling coefficient as well as of flexural transverse buckling coefficient specified for the compressed flange. The conclusive safety condition should be supplemented by the additional interactive component in which the influence of the axial compression force is expressed, in the case when such internal force is induced in a considered beam as a result of thermal strains constrainment.

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Dufour, R., et A. Berlioz. « Parametric Instability of a Beam Due to Axial Excitations and to Boundary Conditions ». Journal of Vibration and Acoustics 120, n^o 2 (1 avril 1998) : 461–67. http://dx.doi.org/10.1115/1.2893852.

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In this paper the stability of the lateral dynamic behavior of a pinned-pinned, clamped-pinned and clamped-clamped beam under axial periodic force or torque is studied. The time-varying parameter equations are derived using the Rayleigh-Ritz method. The stability analysis of the solution is based on Floquet’s theory and investigated in detail. The Rayleigh-Ritz results are compared to those of a finite element modal reduction. It is shown that the lateral instabilities of the beam depend on the forcing frequency, the type of excitation and the boundary conditions. Several experimental tests enable the validation of the numerical results.

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Honig, Jeffrey M., Zachary S. Harper et Gary R. Consolazio. « Influence of Thermal Sweep on Girder Stability during Construction ». Transportation Research Record : Journal of the Transportation Research Board 2672, n^o 41 (4 mai 2018) : 44–55. http://dx.doi.org/10.1177/0361198118768527.

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During construction, girder stability of precast, prestressed concrete bridge girders is adversely affected by fabrication imperfections. Consequently, limits on lateral sweep imperfection caused by fabrication tolerances are imposed by design standards, thus reducing the possibility of girder instability and rollover. However, thermal sweep, induced by solar heating during early stages of construction, can add to pre-existing fabrication tolerances thereby amplifying girder imperfections and reducing stability. In the present study, lateral thermal gradients available in the literature were adopted and enhanced for purposes of computing thermal girder sweep. A variety of girder types—PCI BT-63, Florida-I Beams, and AASHTO Type-V—were then investigated to quantify the influence that lateral thermal sweep has on the stability of individual precast concrete bridge girders under lateral wind load. Previously validated finite element analysis modeling and analysis techniques were used to conduct a parametric study that included 10 girder types, varying span lengths, and five geographic locations. Results revealed that thermal sweep may cause wind carrying capacity reductions of the order of 30 to 60% for typical span lengths, and even greater reductions at span lengths that approach maximum design limits. Consequently, it is crucial that thermal sweep, caused by environmental solar-heating conditions, be considered in construction-stage girder stability analyses.

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Zhao, Guang Hui, Zheng Liang, Fa Guang Jiang, Jia Lin Tian et Liang Zhang. « Out-Plane Stability of Derrick of Inclined Drilling Rig ». Advanced Materials Research 199-200 (février 2011) : 518–21. http://dx.doi.org/10.4028/www.scientific.net/amr.199-200.518.

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K-type derrick of inclined drilling rig that is top driving is usually loaded by axial compression, lateral force and concentrated torque simultaneously, and is more prone to out-plane instability due to its poor torsional rigidity. Here the upper segment of derrick was simplified as cantilever beam-column with laced-bar lattice structure. Stability model was established by energy method, and Ritz method was employed to obtain deformation curves for lateral deflection and torsion. Effects of dip angle of derrick and position of top drive on deformation were analyzed. At last the out-plane instability process of derrick is presented by increasing longitudinal compressive force gradually. For ultimate loads of well drilling condition, out-plane stability requirement of derrick is met.

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Arrais, Flávio, Nuno Lopes et Paulo Vila Real. « Behaviour and resistance of cold-formed steel beams with lipped channel sections under fire conditions ». Journal of Structural Fire Engineering 7, n^o 4 (12 décembre 2016) : 365–87. http://dx.doi.org/10.1108/jsfe-12-2016-025.

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Purpose Steel beams composed of cold-formed sections are common in buildings because of their lightness and ability to support large spans. However, the instability phenomena associated to these members are not completely understood in fire situation. Thus, the purpose of this study is to analyse the behaviour of beams composed of cold-formed lipped channel sections at elevated temperatures. Design/methodology/approach A numerical analysis is made, applying the finite element program SAFIR, on the behaviour of simply supported cold formed steel beams at elevated temperatures. A parametric study, considering several cross-sections with different slenderness’s values, steel grades and bending diagrams, is presented. The obtained numerical results are compared with the design bending resistances determined from Eurocode 3 Part 1-2 and its French National Annex (FN Annex). Findings The current design expressions revealed to be too conservative when compared with the obtained numerical results. It was possible to observe that the FN Annex is less conservative than the Annex E, the first having a better agreement with the numerical results. Originality/value Following the previous comparisons, new fire design formulae are tested. This new methodology, which introduces minimum changes in the existing formulae, provides safety and accuracy at the same time when compared to the numerical results, considering the occurrence of local, distortional and lateral torsional buckling phenomena in these members at elevated temperatures.

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Faruqi, Mohammed, Eliborio Pena et Jina Balogh. « GEOTECHNICAL STRUCTURES : INVESTIGATION OF DRILLED SHAFTS IN HIGHLY EXPANSIVE SOILS ». Engineering Structures and Technologies 6, n^o 2 (6 décembre 2014) : 69–76. http://dx.doi.org/10.3846/2029882x.2014.972633.

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Construction over extremely expansive soils raises the risk of structural foundation failure and potential failure to the building itself. This is due to shrinkage and swell characteristics of expansive soils. This works presents an extensive case study of a distressed building built on drilled piers and expansive soil, and describes innovative practical ideas that can be used in the renovation of its foundation. The building is located west of San Antonio, Texas, USA. This building has experienced significant settlements and differential building movement resulting in widespread building distress. The following foundation based structural distresses were found in the building: 1) vertical movements of more than 300 mm, 2) bearing surface had completely spalled away and the beams were supported solely by bent and corroded anchor bolts which were not well confined in the surrounding concrete, 3) the beam rotations and lateral movement caused the steel stub columns supporting the floor framing to tilt sideways. This created eccentric support conditions that could result in sudden instability failure of either the beams or columns, and 4) under bathrooms in the northwest corner of the building, significant corrosion of steel framing was observed due to long term exposure to moisture leaking through cracks in the floor slab above. Drilled piers were studied using spot study, soil data obtained from boreholes and laboratory tests based on American standards. It is recommended that 0.5 m diameter piers of lengths 18.3 m with positive skin friction to prevent uplift, and a load carrying capacity of 1737 kN be used to rehabilitate the failing foundation. Also, new shafts are to be designed for a minimum factor of safety 2.5 and the rejection of an unacceptable pier required installation of one or more replacement piers at locations that would facilitate load transfer from the structure above.

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Lintz, François, Alessio Bernasconi, Louise Baschet, Céline Fernando, Nazim Mehdi et Cesar de Cesar Netto. « Relationship Between Chronic Lateral Ankle Instability and Hindfoot Varus Using Weight-Bearing Cone Beam Computed Tomography ». Foot & ; Ankle International 40, n^o 10 (28 juin 2019) : 1175–81. http://dx.doi.org/10.1177/1071100719858309.

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Background: Varus hindfoot deformity may increase the risk of chronic lateral ankle instability (CLAI). Our aim was to analyze hindfoot alignment (HFA) in patients with CLAI using weight-bearing cone beam computed tomography (WBCT) to assess this risk. Methods: This retrospective, comparative analysis was carried out using an existing WBCT database (Talas, CurveBeam LLC), including data sets for 370 consecutive feet (189 patients) obtained between July 2016 and October 2018 at a single institution. The software provided semiautomated measurement of HFA, given as foot ankle offset (FAO). Univariate analysis was conducted to compare feet with and without CLAI against sex, age, body mass index, and FAO. Significant variables were included in a multivariable logistic model with random effects to take into account correlation between feet of the same patient. Results: Forty-three feet had CLAI (34 patients). FAO ( P = .0009) was significant for CLAI by univariate analysis. Mean FAO was −2.2% ± 5.5% (varus) and + 2.6% ± 4.7% (valgus) with and without CLAI history, respectively. Multivariable logistic regression adjusted for sex and age demonstrated a 35% increased odds ratio (OR) of CLAI per 1% reduction in FAO value (varus) (adjusted OR=0.64, 95% confidence interval [CI]: 0.49-0.84; P = .001) and no significant effect of sex (adjusted OR=0.52; P = .617) or age (adjusted OR=0.94; P = .165) after adjustment for FAO. Conclusion: A positive relationship was found between varus HFA and the risk to have CLAI. Systematic recording of FAO measurements from WBCT images along with clinical data regarding CLAI history proved successful at quantifying the risk of CLAI. Level of Evidence: Level III, retrospective cohort study.

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DICLELI, MURAT, et ANSHU MEHTA. « SEISMIC RETROFITTING OF CHEVRON-BRACED STEEL FRAMES BASED ON PREVENTING BUCKLING INSTABILITY OF BRACES ». International Journal of Structural Stability and Dynamics 09, n^o 02 (juin 2009) : 333–56. http://dx.doi.org/10.1142/s0219455409003053.

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In this research, a seismic retrofitting method for chevron-braced frames (CBFs) is proposed. The key idea here is to prevent the buckling of the chevron braces via a conventional construction technique that involves a hysteretic energy-dissipating element installed between the braces and the connected beam. The energy-dissipating element is designed to yield prior to buckling of the braces, thereby preventing the lateral stiffness and strength degradation of the CBF caused by buckling, while effectively dissipating the earthquake input energy. Nonlinear static pushover, time history and damage analyses of the CBF and retrofitted CBF (RCBF) are conducted to assess the performance of the RCBF compared with that of the CBF. The results of the analyses reveal that the proposed retrofitting method can efficiently alleviate the detrimental effects of earthquakes on the CBF. The RCBF has a more stable lateral force–deformation behavior with enhanced energy dissipation capability than the CBF. For small-to-moderate intensity ground motions, the maximum interstory drift of the RCBF is close to that of the CBF. But, for high intensity ground motions, it is considerably smaller than that of the CBF. Compared with the CBF under medium-to-large intensity ground motions, the RCBF experiences significantly less damage due to prevention of buckling of the braces.

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Brouzet, C., I. N. Sibgatullin, H. Scolan, E. V. Ermanyuk et T. Dauxois. « Internal wave attractors examined using laboratory experiments and 3D numerical simulations ». Journal of Fluid Mechanics 793 (14 mars 2016) : 109–31. http://dx.doi.org/10.1017/jfm.2016.119.

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In the present paper, we combine numerical and experimental approaches to study the dynamics of stable and unstable internal wave attractors. The problem is considered in a classic trapezoidal set-up filled with a uniformly stratified fluid. Energy is injected into the system at global scale by the small-amplitude motion of a vertical wall. Wave motion in the test tank is measured with the help of conventional synthetic schlieren and particle image velocimetry techniques. The numerical set-up closely reproduces the experimental one in terms of geometry and the operational range of the Reynolds and Schmidt numbers. The spectral element method is used as a numerical tool to simulate the nonlinear dynamics of a viscous salt-stratified fluid. We show that the results of 3D calculations are in excellent qualitative and quantitative agreement with the experimental data, including the spatial and temporal parameters of the secondary waves produced by triadic resonance instability. Further, we explore experimentally and numerically the effect of lateral walls on secondary currents and spanwise distribution of velocity amplitudes in the wave beams. Finally, we test the assumption of a bidimensional flow and estimate the error made in synthetic schlieren measurements due to this assumption.

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Lei, An Qi, Bei Li, Da Tang, Shang Yu Huang, Wei Liu et Chao Zha. « Molecular Dynamics Simulation of Ultrathin Perfluoropolyether Lubricant Depletion under Moving Laser Heating ». Materials Science Forum 921 (mai 2018) : 128–33. http://dx.doi.org/10.4028/www.scientific.net/msf.921.128.

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In this work, molecular dynamics simulations of nanostructured perfluoropolyether (PFPE) lubricants were performed to investigate the depletion instability under rapid scanning laser heating. A modified coarse-gained model was utilized to represent the random copolymer structures of PFPEs. In the simulation, only a partial lubricant near the substrate was irradiated by the laser beam to mimic the nano-scale heat transfer from disk to lubricant. During the laser heating, the surface morphological changes of the PFPE lubricant indicated that the lubricant beads initially raise up and diffuse due to thermal expansion, and then evaporate and form circular ridges around the laser beam center, leading to aggravated depletion. Moreover, the lubricant decomposition was subtle and regarded as negligible; while the raised ridges around the depletion area signified that the non-equilibrium thermo-capillary stress plays an important role in lubricant depletion. The surface temperature contour profiles of the lubricant were evaluated as well. It was showed that the increased temperature is centered around the laser beam and quickly decays toward the ambient temperature, forming non-concentric oval shape distributions and ultrahigh lateral thermal gradients. In addition, the maximum temperature (up to 990 K) was also examined and it is consistent with the ones required by HAMR systems to achieve areal densities beyond 1 Tb/in2.

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Walker, Corey T., Jakub Godzik, David S. Xu, Nicholas Theodore, Juan S. Uribe et Steve W. Chang. « Minimally Invasive Single-Position Lateral Interbody Fusion With Robotic Bilateral Percutaneous Pedicle Screw Fixation : 2-Dimensional Operative Video ». Operative Neurosurgery 16, n^o 4 (30 août 2018) : E121. http://dx.doi.org/10.1093/ons/opy240.

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Abstract Lateral interbody fusion has distinct advantages over traditional posterior approaches. When adjunctive percutaneous pedicle screw fixation is required, placement from the lateral decubitus position theoretically increases safety and improves operative efficiency by obviating the need for repositioning. However, safe cannulation of the contralateral, down-side pedicles remains technically challenging and often prohibitive. In this video, we present the case of a 59-yr-old man with refractory back pain and bilateral lower extremity radiculopathy that was worse on the left than right side. The patient provided written informed consent before undergoing treatment. We performed minimally invasive single-position lateral interbody fusion with robotic (ExcelsiusGPS, Globus Medical Inc, Audubon, Pennsylvania) bilateral percutaneous pedicle screw fixation for the treatment of asymmetric disc degeneration, dynamic instability, and left paracentral disc herniation with corresponding stenosis at the L3-4 level. A left-sided minimally invasive transpsoas lateral interbody graft was placed with fluoroscopic guidance. Without changing the position of the patient or breaking the sterile field, an intraoperative cone-beam computed tomography image was obtained for navigational screw placement with stereotactic trackers in the iliac spine. Screw trajectories were planned using the robotic navigation software and were placed percutaneously in the bilateral L3 and L4 pedicles using the robotic arm. Concomitant lateral fluoroscopy may be used if desired to ensure the fidelity of the robotic guidance. The patient recovered well postoperatively and was discharged home within 36 h, without complication. Single-position lateral interbody fusion and percutaneous pedicle screw fixation can be accomplished using robotic-assisted navigation and pedicle screw placement. Used with permission from Barrow Neurological Institute.

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Zhao, Wu, Quan Bin Zhang, Wei Tao Jia et Zhan Qi Hu. « Influence on BTA Boring Bar Transverse Vibration Considering Inner Cutting Fluid Velocity and Axial Force ». Advanced Materials Research 887-888 (février 2014) : 1215–18. http://dx.doi.org/10.4028/www.scientific.net/amr.887-888.1215.

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A new simulation model on frequency is proposed, to analyze mutual relationship between intrinsic frequency and other factors in system. The study is mainly focused on the axial press effect, inner cutting fluid velocity and its Coriolis inertia effects acting on boring bar. The whole system is assumed to conform to the continuous equal span beam model synthesized with liquid-solid coupling vibration model inner the work and Timoshenko beam model outer the work. Simulations show that system vibration frequency is determined by mechanical properties, axial force, inner cutting fluid velocity and density. Three aspects influence BTA boring bar lateral vibration considering inner cutting fluid velocity and axial force, who are transverse inertial mass, inertia and self-excited vibration on the bar. Inner flowing of the cutting fluids also lead to instability on bar.

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Kwok, L. P., et C. F. Chen. « Stability of Thermal Convection in a Vertical Porous Layer ». Journal of Heat Transfer 109, n^o 4 (1 novembre 1987) : 889–93. http://dx.doi.org/10.1115/1.3248199.

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Experiments were carried out to study the stability of thermal convection generated in a vertical porous layer by lateral heating in a tall, narrow tank. The porous medium, consisting of glass beads, was saturated with distilled water. It was found that the flow became unstable at a critical ΔT of 29.2°C (critical Rayleigh number of 66.2). Linear stability analysis was applied to study the effects of the Brinkman term and of variable viscosity separately using a quadratic relationship between the density and temperature. It was found that with the Brinkman term, no instability could occur within the allowable temperature difference across the tank. With the effect of variable viscosity included, linear stability theory predicts a critical ΔT of 43.4°C (Rayleigh number of 98.3).

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Villalba, Ignacio, Ricardo Insa, Pablo Salvador et Pablo Martinez. « Methodology for evaluating thermal track buckling in dual gauge tracks with continuous welded rail ». Proceedings of the Institution of Mechanical Engineers, Part F : Journal of Rail and Rapid Transit 231, n^o 3 (4 août 2016) : 269–79. http://dx.doi.org/10.1177/0954409715626957.

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In the National Spanish railway network, two types of track gauge with continuous welded rails are currently in use: the “Iberian” wide gauge (1668 mm) and the standard gauge (1435 mm). In order to improve links and freight traffic between different lines and with the rest of Europe, a dual gauge track with three rails was developed. This solution modifies the classical track configuration, so it is necessary to develop new methodologies and studies to understand its behavior. Among other loads applied on a continuous welded rail track, a considerable rise in temperature induces compressive stresses in the three rails that can lead to lateral track buckling. Moreover, on dual gauge tracks, the addition of the third rail increases the axial compression, which may lead to track instability. For this reason, a three-dimensional continuous welded rail model is developed in this study to be used for dual gauge track buckling analysis on straight tracks subjected to temperature load. The continuous welded rail dual gauge track model consists of beam, solid and spring elements, in which a non-linear behaviour of the ballast is considered. The results obtained may be used to predict the buckling capacity of the continuous welded rail on dual gauge tracks with respect to different parameters such as lateral resistance, lateral imperfections, sleeper spacing or torsional stiffness.

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Wikstrom, Erik A., Tricia Hubbard-Turner, Sophie Guderian et Michael J. Turner. « Lateral Ankle Sprain in a Mouse Model : Lifelong Sensorimotor Dysfunction ». Journal of Athletic Training 53, n^o 3 (1 mars 2018) : 249–54. http://dx.doi.org/10.4085/1062-6050-365-16.

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Context: Ankle sprains are the most common orthopaedic injury that occurs during sport and physical activity. Many individuals who sprain their ankles develop chronic ankle instability (CAI), a condition characterized by recurrent injury, decreased physical activity, and decreased quality of life. These residual impairments are believed to persist for the remainder of the patient's life, in part due to the link between CAI and posttraumatic ankle osteoarthritis. However, this belief remains speculative due to the lack of long-term prospective investigations. Objective: To use a mouse model of mild (MILD) and severe (SEVERE) ankle sprains to quantify balance and locomotor adaptations across the lifespan. Design: Cohort study. Setting: University research laboratory. Patients or Other Participants: Fifty male mice (CBA/J) were randomly placed into a control (SHAM), MILD, or SEVERE group and housed individually. Intervention(s): The MILD group underwent surgical transection of a single right hind-limb lateral ankle ligament, and the SEVERE group had 2 of the lateral ligaments transected. The SHAM group underwent a sham surgery during which no lateral ligaments were transected. Main Outcome Measure(s): After surgically inducing the ankle sprain, we measured balance and gait using a balance beam and footprint test before and every 6 weeks for 78 weeks. Results: Age-related declines in balance but not stride length were exacerbated by an ankle sprain (P < .001). Balance and stride lengths changed with age (P < .001). Foot slips were worse in the SEVERE (4.32 ± 0.98) and MILD (3.53 ± 0.98) groups than in the SHAM group (2.16 ± 0.99; P < .001). Right-limb stride length was shorter in the SEVERE group (6.45 cm ± 0.41 cm) than in the SHAM group (6.87 cm ± 0.40 cm; P = .04). Conclusions: Transecting the lateral ligaments of a mouse hind foot resulted in lifelong sensorimotor dysfunction. Declines starting at 42 weeks postinjury may have represented the onset of posttraumatic osteoarthritis.

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Fu, X., G. L. Tan, R. Gordon et J. M. Xu. « Third-order nonlinearity induced lateral-mode frequency locking and beam instability in the high-power operation of narrow-ridge semiconductor lasers ». IEEE Journal of Quantum Electronics 34, n^o 8 (1998) : 1447–54. http://dx.doi.org/10.1109/3.704339.

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Taha, Mohamed. « Recursive Differentiation Method for Boundary Value Problems : Application to Analysis of a Beam-Column on an Elastic Foundation ». Journal of Theoretical and Applied Mechanics 44, n^o 2 (1 juin 2014) : 57–70. http://dx.doi.org/10.2478/jtam-2014-0010.

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Abstract In the present work, the recursive differentiation method (RDM) is introduced and implemented to obtain analytical solutions for differential equations governing different types of boundary value prob- lems (BVP). Then, the method is applied to investigate the static behaviour of a beam-column resting on a two parameter foundation subjected to different types of lateral loading. The analytical solutions obtained using RDM and Adomian decomposition method (ADM) are found similar but the RDM requires less mathematical effort. It is indicated that the RDM is reliable, straightforward and efficient for investigation of BVP in finite domains. Several examples are solved to describe the method and the obtained results reveal that the method is convenient for solving linear, nonlinear and higher order ordinary differential equations. However, it is indicated that, in the case of beam-columns resting on foundations, the beam-column may be buckled in a higher mode rather than a lower one, then the critical load in that case is that accompanies the higher mode. This result is very important to avoid static instability as it is widely common that the buckling load of the first buckling mode is always the smaller one, which is true only in the case of the beam-columns without foundations.

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Koster, A. J., J. Walz, U. Ziese, A. Stoschek, R. Hegerl, D. Typke, J. Kleinz et W. Baumeister. « Automated electron tomography and CCD spot-scan imaging of biological macromolecules ». Proceedings, annual meeting, Electron Microscopy Society of America 52 (1994) : 120–21. http://dx.doi.org/10.1017/s0424820100168335.

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Computer control of a transmission electron microscope (TEM) and digital recording of images have shown to be useful tools in recording 2D data sets of macromolecules and larger cellular structures with accurately defined imaging conditions.3D structure of individual molecules can be obtained by electron tomography. The method requires that projection data are collected over a large range of specimen tilts. With automated electron tomography images are recorded in digital format, and lateral specimen displacement together with focus changes are automatically compensated for. Typically, with our experimental set-up, we collect 75 projections of negatively stained preparations over ±75° and 30 projections of ice-embedded molecules over ±60° with a total dose of 20-50 e/Å2.By using the spot-scan imaging mode beam-induced movements of ice-embedded specimens are greatly reduced, thus largely avoiding the loss of resolution associated with specimen instability. With CCD spot-scan imaging the size of the spot is matched to the CCD chip (Fig. 1).

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Wang, Xinfeng, Mingyuan Lu, Yuhao Gao, Wenbo Luo et Wengang Liu. « Structural Mechanical Characteristics and Instability Law of Roof Key Block Breaking in Gob-Side Roadway ». Advances in Civil Engineering 2020 (15 décembre 2020) : 1–12. http://dx.doi.org/10.1155/2020/6682303.

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The influence of mining on the upper section of working face leads to the fracture of the lateral key block of the roof. From the goaf to the coal body, a group of “left-middle-right” key blocks are formed. According to the three different spatial position structure relations formed by roadway and broken key block in practical engineering, the mechanical causes of broken structure of key block in roof of roadway along goaf are analyzed. FLAC3D is used to simulate and analyze the deformation characteristics and stress state of key block structure model before and after roadway excavation, and the mechanical characteristics and instability mechanism of key block sliding and breaking under three spatial structure modes are obtained. With the help of the mathematical model of material mechanics, the structural mechanical behavior of key block model of roof before and after roadway excavation and the temporal and spatial evolution law of unloading and breaking are studied. The results show that the complex influence factors of mining disturbance and low strength of the weak rock mass will weaken the internal balance of “masonry beam” structure. When the roadway is located below the fracture line of the key block, the middle key block will rotate and lose stability with the side hinge joint of the goaf as the axis; when the roadway is located in the fracture line of the key block, it is easy for the middle key block to slide and lose stability; when the roadway is located outside the fracture line of the key block, the middle key block is in the state of complete collapse, the mechanical transmission mechanism of the surrounding rock in the vertical direction is weakened, and the surrounding rock is the most stable.

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Răcănel, Ionuţ Radu, Vlad Daniel Urdăreanu et Andrei Radu. « “Bowstring” Arches in Langer System Without Wind Bracing ». Romanian Journal of Transport Infrastructure 4, n^o 1 (1 juillet 2015) : 67–77. http://dx.doi.org/10.1515/rjti-2015-0032.

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Abstract Arch bridges are slender structures and can be efficiently used in the range of medium to large spans. These structures have an improved aesthetic aspect and in the same time a low construction height, with obvious advantages regarding reduced costs in the infrastructuers and their foundations. For this type of structures usually composite or orthotropic decks are used. Lately, innovative solutions have been used in designing arch bridges, especially discarding the top wind bracing system. The level of axial forces and bending moments in the arches and tie imply the design of sections with sufficient stiffness and strength in both directions in order to ensure the general stability of the arches, without the need for top wind bracing. Moreover, the cross section of the arches is not constant, but shifts in accordance with the variation of the bending moments, in order to ensure their lateral stability. This paper studies a road bridge with parallel Bowstring arches, with a span of 108m and a carriageway 7.00m wide, sustained by a deck made up of crossbeams 2m apart and a concrete slab. The main beams are held by ties arranged in the Langer system, 10 to 14m apart from each other. The sag of the arches is 18m high. The analyzed structure was proposed for construction in the city of Oradea and is used for crossing the “Crişul Repede” river, between Oneştilor street on the left bank and the Sovata, Fagului and Carpaţi streets on the right bank. The performed analyses have the following two main objectives: to establish the critical load for which the failure of the arches occurs by instability and to underline the influence of different wind bracing systems on the bridge’s collapse loads respectively.

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Sibgatullin, I. N., E. V. Ermanyuk, K. A. Vatutin, D. A. Ryazanov et X. Xu. « NUMERICAL SIMULATION OF THREE-DIMENSIONAL WAVE ATTRACTORS ». XXII workshop of the Council of nonlinear dynamics of the Russian Academy of Sciences 47, n^o 1 (30 avril 2019) : 112–15. http://dx.doi.org/10.29006/1564-2291.jor-2019.47(1).35.

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Internal and inertial waves obey very specific dispersion relation, which defines the direction of wave propagation with respect to the gravity or axis of rotation, but which does no define the wavelength. Particular cases of scale effects are described in (Brouzet et al., 2017). In closed geometrics the presence of a monochromatic wavemaker can produce wave beams, which after multiple reflections from the boundaries may approach a closed loop – the wave attractor. In ideal fluids the concentration of energy on the wave attractor can grow without any limits. In viscous stratified or rotating fluids the concentration will be balanced with dissipation due to viscosity, which results in appearance of wave attractors of finite width. The characterization of the flow with the Reynolds number based on the boundary conditions is questionable in this case, since on the attractor the velocity can be several times magnified. When the wave beam is reflected from an inclined plane, the horizontal component of velocity rotates, as was first described by O. Phillips, while preserving the angle with the gravity or axis of rotation. With the help of ray tracing it can be shown that due to this effect the three-dimensional accumulation of wave energy can occur. First qualitative and quantitative correspondence of laboratory and numerical simulation of wave attractors in the pseudo-2D laboratory tank with trapezoidal section was described in (Brouzet et al., 2016), and importance of dissipation on the lateral boundaries was shown (F. Beckebanze et al., 2018). For high Schdmidt number there appear the folded structures, which can interact with the background wave motion (Sibgatullin, Kalugin 2016). In (Brouzet et al., 2016b), (Dauxois et al., 2018) cascade of triadic resonances in (1,1) produced by a wave attractor was demonstrated. Three-dimensional accumulation of wave energy in trapezoidal frustum with a localized wavemaker was investigated in (Pillet et al., 2018). Numerical simulations of the present work had showed the importance of phase shift in transversal direction. An attractor can have the same form as the 2D attractor in any given longitudinal cut, but the phase of oscillation can change up to counter-phase. Interplay of 3D concentration of waves beams, dissipation and phase shifting impact the final energy distribution in transversal direction. First three-dimensional simulations (Sibgatullin et al., 2017) of tidal and symmetric forcing on the rotating layer of fluid with inclined walls showed three-dimensional twisted structure of waves attractors for precession of one boundary of the layer in opposite direction to the rotation of the layer. With growth of the amplitude of the external forcing the the instability of triadic resonance appears, but in contrast to the internal wave attractors, triadic resonances take place in azimuthal (transversal to the trapeze) section. The turbulent regimes generated by the background wave attractors are studied, with analysis of full power income and total dissipation. The research was supported by the Program of Fundamental Research of the Presidium of the Russian Academy of Sciences No. 26

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Miller, Adam, et Steven M. Raikin. « Lateral Ankle Instability ». Operative Techniques in Sports Medicine 22, n^o 4 (décembre 2014) : 282–89. http://dx.doi.org/10.1053/j.otsm.2014.09.008.

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Taghavi, Cyrus E., et Nelson F. SooHoo. « Lateral ankle instability ». Current Orthopaedic Practice 20, n^o 2 (avril 2009) : 117–22. http://dx.doi.org/10.1097/bco.0b013e31819bca87.

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King, Jeffrey C., et Edwin E. Spencer. « Lateral Ligamentous Instability ». Techniques in Orthopaedics 15, n^o 2 (juin 2000) : 93–104. http://dx.doi.org/10.1097/00013611-200015020-00002.

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Bouché, Richard T., Doug Richie et James G. Garrick. « Lateral Ankle Instability ». Foot & ; Ankle Specialist 6, n^o 3 (23 avril 2013) : 206–13. http://dx.doi.org/10.1177/1938640013485223.

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Clitherow, Harry Dominic Stracey, Duncan Thomas McGuire et Gregory Ian Bain. « Lateral elbow instability ». Asia-Pacific Journal of Sports Medicine, Arthroscopy, Rehabilitation and Technology 1, n^o 1 (janvier 2014) : 11–18. http://dx.doi.org/10.1016/j.asmart.2013.12.003.

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Shakoor, Delaram, Greg Osgood, Jakrapong Orapin, Iman Khodarahmi Qahnavieh, Gaurav Thawait, James Ficke, Lew Schon et Shadpour Demehri. « Comparison Between Weightbearing and Non-weightbearing Measurements for Evaluation of Tibiofibular Syndesmotic Injuries ». Foot & ; Ankle Orthopaedics 3, n^o 3 (1 juillet 2018) : 2473011418S0010. http://dx.doi.org/10.1177/2473011418s00109.

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Category: Ankle Introduction/Purpose: The distal tibiofibular syndesmosis maintains the integrity of ankle mortise during weight bearing. Syndesmotic injuries are common and even slight malreduction are associated with long-term development of tibiotalar osteoarthritis. Radiographic as well as CT based measurements are being employed to detect syndesmotic injuries, however, subtle injuries are commonly overlooked. In the present study we intend to investigate whether measurements obtained from weight-bearing (WB) cone-beam computed tomography (CBCT) images are different from measurements obtained from NWB images in subjects with clinical suspicion of syndesmotic injury and “inconclusive” plain radiograph findings Methods: In this prospective study, following IRB approval, the injured ankles of 20 patients (10 men and 10 women; mean age: 46.1 years; range: 19-82) with persistent ankle pain following ankle trauma and clinical suspicion of syndesmotic injury underwent simultaneous WB and NWB CBCT scans. Following a detailed literature review, a set of 21 syndesmotic related measurements in all WB and NWB images, assessing fibular displacement in medio-lateral, cranio-caudal, antero-posterior planes were performed by three independent readers. Inter-observer and intra-observer reliabilities were evaluated by intra-class correlation (ICC) and Pearson/Spearman’s correlation, respectively. We used Paired student t-tests or Wilcoxon-rank-sum tests to compare the measurements from the two scans. Bootstrapping with 10000 samples was used to extract P-values for 99% uncertainty levels Results: we observed almost perfect intra-observer reliability for WB and NWB measurements (r = 0.8-0.98). Inter-observer reliability was significant for all measurement with overall fair to perfect agreement (ICC=0.36-0.97). Mean values of medio-lateral measurements including posterior tibiofibular distance, tibiofibular clear space and diastasis were significantly higher in WB images compared to NWB CBCT images (P-value< 0.05). Mean values of angular measurement, bi-malleolar angle, lateral clear space and fibular length were significantly lower in WB images (P-value<0.05). The difference between other measurements were not statistically significant. Conclusion: Of syndesmotic measurements available in the literature, certain measurements are different between WB and NWB CBCT examinations with moderate to perfect intra- and inter-observer reliability in post-traumatic ankles with clinical suspicion of syndesmotic injury and inconclusive plain radiographs. These measurements should be further investigated for detection of biomechanical instability associated with syndesmotic injury compared to those obtained from asymptomatic ankles

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Albuquerque, Samuel S. C., Brena P. Rocha, Raquel F. Albuquerque, Juceli S. Oliveira, Rosane M. T. Medeiros, Franklin Riet-Correa, Joaquim Evêncio-Neto et Fábio S. Mendonça. « Spontaneous poisoning by Ricinus communis (Euphorbiaceae) in cattle ». Pesquisa Veterinária Brasileira 34, n^o 9 (septembre 2014) : 827–31. http://dx.doi.org/10.1590/s0100-736x2014000900004.

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The aim of this study is to report cases of spontaneous poisoning of cattle by Ricinus communis (castor beans) in Paraíba, a semiarid region of northeastern Brazil. The cases were observed in 2 herds on neighboring properties in 2013. Clinical signs developed within 6-24 h and consisted of weakness, tachycardia, dyspnea, profuse watery diarrhea, dehydration, depression, instability, cramps, permanent lateral recumbency and death within 48-72 h. Of the 60 cattle at risk, 19 were affected and 14 died. Five fully recovered after the course of 12 days. Three animals were necropsied. The main gross lesions were hemopericardium, hemothorax, pulmonary edema, petechial hemorrhages in the epicardium and endocardium, ecchymoses at the papillary muscles and suffusions on the intercostal muscles. Hemorrhages were also observed in the abdominal cavity, spleen and mucosa of the abomasum and small intestine. The rumen content was liquid with a large amount of castor bean seeds. There were circular, whitish and focally diffuse areas in the liver parenchyma. The main microscopic lesions consisted of multifocal coagulative myocardial necrosis with the presence of mononuclear cell infiltration and varying degrees of bleeding between cardiac muscle fibers. The abomasum and small intestine mucosae and submucosa had mild edema and mononuclear and polymorphonuclear inflammatory cell infiltration. The diagnosis of R. communis was based on the history of plant consumption, clinical signs, pathology of the disease and the presence of large amounts of castor bean seeds in the forestomachs.

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Maffulli, Nicola, Umile Giuseppe Longo, Stefano Petrillo et Vincenzo Denaro. « (iii) Lateral ankle instability ». Orthopaedics and Trauma 26, n^o 1 (février 2012) : 20–24. http://dx.doi.org/10.1016/j.mporth.2012.01.003.

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