Application of deterministic and stochastic analysis to calculate a stadium with pressure measurements in wind tunnel

peer reviewedThis paper aims at comparing different analysis methods in the design of a roof subjected to buffeting wind forces. The specificity of this study is that pressures acting on the stadium roof are measured in a wind tunnel. The key idea is to fit a probabilistic model onto the measured data and to perform the stochastic analysis as a usual buffeting analysis

Mitigation of the torsional flutter phenomenon of bridge deck section during a lifting phase

This paper presents a complete analysis of the aeroelastic behaviour of a deck section during the construction stage of the Third Bosphorus Bridge in Istanbul, Turkey. The combination of the low torsional stiffness along the vertical axis and the unstable aerodynamic shape of the suspended deck section led to a torsional flutter instability for a low wind speed (9.6 m/s). This low critical wind speed was obviously very likely to occur on the site of construction, so that mitigation actions were be implemented. It was decided to cover partially the sides of the deck section in order to modify adequately its aerodynamic shape. It is demonstrated that the proposed aerodynamic counter-measures increase the critical torsional flutter wind speed up to 39.5 m/s (worst configuration), which is acceptable for the construction phase of the bridge. The proposed mitigation solution was implemented and no torsional oscillations were observed

Importance of modal cross-correlations on wind loaded structures

peer reviewedIn civil engineering applications the dynamic analysis of large structure is often performed in a modal space. This method is known to offer an interesting decrease of the number of degrees of freedom as well as a decomposition of the structure’s response in “uncoupled” components. Even if the response in each mode can be computed independently from the responses in the other ones, in the context of stochastic loading, the coherence of these modal responses must be accounted for in the determination of the structural response. These quantities are known as the modal cross-correlations. In this paper we will show that these crosscorrelations can be important (contrarily to what is sometimes thought) even in case of wellseparated natural frequencies. This will be illustrated on the analysis of the famous Viaduct of Millau during an erection stage

Etude expérimentale et numérique du comportement des structures composées de barres à assemblages semi-rigides

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Effect of initial imperfections in numerical simulations of collapse behaviour of stiffened plates under compression

peer reviewedThe slenderness of plated structures together with a generalised use of high strength steel leads to a great importance of stability phenomena. The practical way to deal with such problems is to use rules proposed in design codes. A common alternative to design codes is the use of non linear finite element simulations. One of the most sensitive point in these simulations is the choice of the initial imperfections to be introduced in the model. The present paper discusses the effect of initial imperfections on the calculated collapse load. Several parameters are considered (shape, magnitude and direction). Results of numerical simulations are also compared with those of a design using Eurocode 3 or ECCS Recommendations. Two cases of plate geometry are studied (plate with one single stiffener and plate with multiple stiffeners)

Buckling curves for lateral torsional buckling of unrestrained beams

In Eurocode 3 two methods to determine the ultimate lateral torsional buckling load of steel beams in bending are presented: the General and the Specific Methods. Both methods make use of buckling curves, but the curves to be used are different for both methods. The ultimate lateral torsional buckling load can also be calculated using the Finite Element Method (FEM) by means of a geometrical and material non-linear analysis on a beam including imperfections (GMNIA). This paper compares the ultimate loads based on the design rules in Eurocode 3 for lateral torsional buckling of unrestrained beams in bending to the ultimate loads obtained with Finite Element simulations on the basis of a parameter study. It is concluded that the Specific Method gives a large over-estimation of the ultimate load found with FEM simulations, while the General Method gives good results. Therefore, Nationally Determined Parameters in the Specific Method should be chosen with care in the National Annexes

A generalised mechanical model for the characterisation of steel joints

peer reviewedComponent-based mechanical models compliant with Eurocode 3 becomes a popular alternative to complex Finite Element (FE) analyses for characterising the behaviour of steel joints. However, several key aspects are not accommodated by the existing spring models, i.e., group mechanisms, component interactions, and the variation of the shear force on the height of the column web panel. This paper introduces an innovative mechanical model suitable for the characterisation of structural joints under generalised loading. The model relies on the principles of the Component Method and incorporates the features systematically disregarded in the classical spring models. This guarantees code-compliant predictions, and by virtue of its universality, the model can be used for any loading protocol (bending moment - sagging or hogging, axial force, bending moment + axial force). Conclusive evidence given by comparisons with experimental data and analytical results shows the compliance of the proposed model with the Eurocode 3 and proves its accuracy in predicting the actual behaviour of steel joints. The proposed modelling method-ology allows integrating the model as a macro-element in dedicated software, thus presenting promising perspectives for reliable and time efficient structural analyses

Modélisation 3D d’un groupe de pieux pour le pont-canal de Houdeng

peer reviewedA satisfactory prediction of the settlements of hyperstatic structures is becoming more and more important in their design and construction. In this paper, the problems related to the behaviour of a group of piles and to the quality of the drilled piles of the canal-bridge of Houdeng (Belgium) are analysed in a non conventional fashion, based on a finite element analysis, thanks to sufficient experimental data. The influence of an imperfectly cleaned excavation bottom and of the destructuration of the bottom rocks caused by the drilling of the piles is investigated. A particular attention is also given to the behaviour of a group of piles

Prognosis of Children Undergoing Liver Transplantation: A 30-Year European Study

OBJECTIVES: The European Liver Transplant Registry has been collecting data on virtually all pediatric liver transplant (PLT) procedures in Europe since 1968. We analyzed patient outcome over time and identified parameters associated with long-term patient outcome. METHODS: Participating centers and European organ-sharing organizations provided retrospective data to the European Liver Transplant Registry. To identify trends, data were grouped into consecutive time spans: era A: before 2000, era B: 2000 to 2009, and the current era, era C: since 2010. RESULTS: From June 1968 until December 2017, 16 641 PLT were performed on 14 515 children by 133 centers. The children <7 years of age represented 58% in era A, and 66% in the current era (P <.01). The main indications for PLT were congenital biliary diseases (44%) and metabolic diseases (18%). Patient survival at 5 years is currently 86% overall and 97% in children who survive the first year after PLT. The survival rate has improved from 74% in era A to 83% in era B and 85% in era C (P <.0001). Low-volume centers (<5 PLT/year) represented 75% of centers but performed only 19% of PLT and were associated with a decreased survival rate. In the current era, however, survival rates has become irrespective of volume. Infection is the leading cause of death (4.1%), followed by primary nonfunction of the graft (1.4%). CONCLUSIONS: PLT has become a highly successful medical treatment that should be considered for all children with end-stage liver disease. The main challenge for further improving the prognosis remains the early postoperative period