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Behaviour of steel joints under fire loading
Luís Simões da Silva,Aldina Santiago,Paulo Vila Real,David Moore 국제구조공학회 2005 Steel and Composite Structures, An International J Vol.5 No.6
This paper presents a state-of-the-art on the behaviour of steel joints under fire loading and some recent developments in this field, currently being carried out by the authors. Firstly, a review of the experimental research work on steel joints is presented, subdivided into isolated member tests, sub-structure tests and tests on complete building structures. Special emphasis is placed on the seventh Cardington test, carried out by the authors within a collaborative research project led by the Czech Technical University in Prague. Secondly, a brief review of various temperature distributions within a joint is presented, followed by a discussion of the behaviour of isolated joints at elevated temperature, focussing on failure modes and analytical procedures for predicting the moment-rotation behaviour of joints at elevated temperature. Finally, a description of the coupled behaviour of joints as part of complete structures is presented, describing previous work and investigations on real fire (including heating and cooling phases) currently being carried out by the authors.
Behaviour of flush end-plate beam-to-column joints under bending and axial force
Luís Simões da Silva,Luciano R. O. de Lima,Pedro C. G. da S. Vellasco,Sebastião A. L. de Andrade 국제구조공학회 2004 Steel and Composite Structures, An International J Vol.4 No.2
Steel beam-to-column joints are often subjected to a combination of bending and axial forces. The level of axial forces in the joint may be significant, typical of pitched-roof portal frames, sway frames or frames with incomplete floors. Current specifications for steel joints do not take into account the presence of axial forces (tension and/or compression) in the joints. A single empirical limitation of 10% of the beam’s plastic axial capacity is the only enforced provision in Annex J of Eurocode 3. The objective of the present paper is to describe some experimental and numerical work carried out at the University of Coimbra to try to extend the philosophy of the component method to deal with the combined action bending moment and axial force.
Endovascular treatment of residual or recurrent intracranial aneurysms after surgical clipping
da Silva Júnior Nilton Rocha,Trivelato Felipe Padovani,Nakiri Guilherme Seizem,Rezende Marco Túlio Salles,de Castro-Afonso Luís Henrique,Abud Thiago Giansante,Vanzin José Ricardo,Manzato Luciano Bambi 대한뇌혈관외과학회 2021 Journal of Cerebrovascular and Endovascular Neuros Vol.23 No.3
Objective Total aneurysm occlusion is crucial for the prevention of rebleeding of a ruptured aneurysm or to avoid rupture of an unruptured lesion. Both surgical and endovascular embolization fail to achieve complete aneurysm occlusion in all the cases. The objective of the study was to establish the safety and efficacy of endovascular treatment for previously clipped residual or recurrent aneurysms. Methods This was an observational, retrospective study of patients harboring incompletely occluded intracranial aneurysms after clipping who underwent endovascular treatment. Patients were treated using 4 different techniques: (1) simple coiling, (2) balloon remodeling, (3) stent-assisted coiling, and (4) flow diversion. Analyses were performed to identify predictors of total aneurysm occlusion, recanalization and complications. Results Between May 2010 and September 2018, 70 patients harboring incompletely occluded intracranial aneurysms after clipping met the inclusion criteria in 5 centers. The mean residual aneurysm size was 7.5 mm. Fifty-nine aneurysms were unruptured. Total aneurysm occlusion was achieved in 75.3% of the aneurysms after 1 year. All aneurysms treated with flow diversion revealed complete occlusion according to control angiography. Recanalization was observed in 14.5%. Permanent morbidity and mortality occurred in 2.9% and 1.4% of the patients, respectively. Conclusions Endovascular treatment of recurrent or residual aneurysms after surgical clipping was safe and efficacious. Flow diversion seems to be associated with better anatomical results. A more rigid study, a larger group of patients, and long-term follow-up are required to provide stronger conclusions about the best approach for residual clipped aneurysms.
Luís Simões da Silva,Trayana Tankova,Carlos Rebelo 한국강구조학회 2020 International Journal of Steel Structures Vol.20 No.1
This paper presents the safety assessment of Eurocode 3—part 1-1 (Eurocode in EN 1993-1-1, Eurocode 3: design of steel structures—part 1-1: general rules and rules for buildings, CEN, Brussels, 2005) rules for hot-rolled members with I and H cross-sections loaded in bending and compression. The safety assessment follows the recommendations of Annex D of EN 1990 (Eurocode in EN 1990, Eurocode—basis of structural design, CEN, Brussels, 2002). It is based on a large number (11,345) of numerical simulations (GMNIA) covering various relevant parameters. The assessment aimed at the justifi cation of the partial factors to be used in the design of members under bending and compression as part of the ongoing process of revision of Eurocode 3—part 1-1. For that, it covered the application of the interaction factors given in Annex B/Method 2 of the current version of Eurocode 3—part 1-1 which will be the only method in the future version of Eurocode 3. In addition, the interaction factors were applied with the new buckling curves for lateral-torsional buckling, as they will appear in the new version. The assessment showed consistent results across the subsets considered with low variability and partial factors generally lower than 1.0. Finally, the γ M * values are compared for fl exural buckling of columns, lateral-torsional buckling of beams with the results obtained for beam-columns considering f y , cross-section geometry and E as random variables, using the same statistical characterization of the random variables. It is observed that the partial factors obtained beam-columns are lower than those obtained for columns and beams. In conclusion, based on combination of the results obtained it was possible to recommend a global value of γ M1 = 1.0.
Lincon Rafael da Silva,Leonardo Luís de Barros Rodrigues,Amanda Silva Botelho,Bruna Sartório de Castro,Paulo Henrique Pereira Costa Muniz,Maria Carolina Blassioli Moraes,Sueli Corrêa Marques de Mello 한국식물병리학회 2023 Plant Pathology Journal Vol.39 No.1
Common bean (Phaseolus vulgaris L.) is one of the most important crops in human food production. The occurrence of diseases, such as white mold, caused by Sclerotinia sclerotiorum can limit the production of this legume. The use of Trichoderma has become an important strategy in the suppression of this disease. The aim of the present study was to evaluate the effect of volatile organic compounds (VOCs) emitted by Trichoderma azevedoi CEN1241 in five different growth periods on the severity of white mold in common bean. The in vitro assays were carried out in double-plate and split-plate, and the in vivo assays, through the exposure of the mycelia of S. sclerotiorum to the VOCs of T. azevedoi CEN1241 and subsequent inoculation in bean plants. Chemical analysis by gas chromatography coupled to mass spectrometry detected 37 VOCs produced by T. azevedoi CEN1241, covering six major chemical classes. The profile of VOCs produced by T. azevedoi CEN1241 varied according to colony age and was shown to be related to the ability of the biocontrol agent to suppress S. sclerotiorum. T. azevedoi CEN1241 VOCs reduced the size of S. sclerotiorum lesions on bean fragments in vitro and reduced disease severity in a greenhouse. This study demonstrated in a more applied way that the mechanism of antibiosis through the production of volatile compounds exerted by Trichoderma can complement other mechanisms, such as parasitism and competition, thus contributing to a better efficiency in the control of white mold in bean plants.
On the rate of convergence of uniform approximations for sequences of distribution functions
João Lita da Silva,Luís Pedro Ramos 한국통계학회 2014 Journal of the Korean Statistical Society Vol.43 No.1
In this paper, we develop uniform bounds for the sequence of distribution functions ofg(Vn + μn), where g is some smooth function, {Vn, n ≥ 1} is a sequence of identicallydistributed random variables with common distribution having a bounded derivative and{μn} are constants such that μn → ∞. These bounds allow us to identify a suitablesequence of random variables which is asymptotically of the same type of g(Vn + μn)showing that the rate of convergence for these uniform approximations depends on theratio of the second derivative to the first derivative of g. The corresponding generalizationto the multivariate case is also analyzed. An application of our results to the STATIS-ACTmethod is provided in the final section.
Rayleigh-Ritz procedure for determination of the critical load of tapered columns
Liliana Marques,Luís Simões da Silva,Carlos Rebelo 국제구조공학회 2014 Steel and Composite Structures, An International J Vol.16 No.1
EC3 provides several methodologies for the stability verification of members and frames. However, when dealing with the verification of non-uniform members in general, with tapered cross-section, irregular distribution of restraints, non-linear axis, castellated, etc., several difficulties are noted. Because there are yet no guidelines to overcome any of these issues, safety verification is conservative. In recent research from the authors of this paper, an Ayrton-Perry based procedure was proposed for the flexural buckling verification of web-tapered columns. However, in order to apply this procedure, Linear Buckling Analysis (LBA) of the tapered column must be performed for determination of the critical load. Because tapered members should lead to efficient structural solutions, it is therefore of major importance to provide simple and accurate formula for determination of the critical axial force of tapered columns. In this paper, firstly, the fourth order differential equation for non-uniform columns is derived. For the particular case of simply supported web-tapered columns subject to in-plane buckling, the Rayleigh-Ritz method is applied. Finally, and followed by a numerical parametric study, a formula for determination of the critical axial force of simply supported linearly web-tapered columns buckling in plane is proposed leading to differences up to 8% relatively to the LBA model.
Pedro Nogueiro,Luís Simões da Silva,Rita Bento,Rui Simões 국제구조공학회 2009 Steel and Composite Structures, An International J Vol.9 No.1
Composite joints, considering the composite action of steel and concrete, exhibit, in general, high strength and high ductility. As a consequence, the use of this type of joint has been increasing in many countries, especially in those that are located in earthquake-prone regions. In this paper, a hysteretic model with pinching is presented that is able to reproduce the cyclic response of steel and composite joints. Secondly, the computer implementation and adaptation of the model in a spring element within the computer code. Seismosoft is described. The model is subsequently calibrated using a series of experimental test results for composite joints subjected to cyclic loading. Finally, typical parameters for the various joint configurations are proposed.
Cyclic behaviour of end-plate beam-to-column composite joints
Rui Simões,Luís Simões da Silva,Paulo J.S. Cruz 국제구조공학회 2001 Steel and Composite Structures, An International J Vol.1 No.3
An experimental research program on end-plate beam-to-column composite joints under cyclic loading is presented. The major focus relates to the identification of the contribution of the concrete confinement in composite columns to the behaviour of the joint, on internal nodes and external nodes, together with an assessment of degradation of strength and stiffness in successive loading cycles. From the experimental results it was possible to identify the various failure modes and to fit the corresponding hysteretic curves to the Richard-Abbott and Mazzolani models. These curve-fitting exercises highlighted the need to adapt both models, either for improved ease of application, or to deal with some aspects previously not covered by those models.