1,721,069 research outputs found
Effective slab width in twin-gider composite decks
No full textA theoretical model recently proposed by the authors for the visco-elastic analysis of steel-concrete composite beams with flexible shear connection is generalised in order to investigate the shear-lag effect in twin-girder composite decks under static, geometrical, and thermal actions. A suitable warping function is derived to catch the effect of the real beam position. Some applications are carried out on a realistic bridge deck and comparisons between results provided by the proposed model and those given by the EC4-2 method are performed
Shear-lag effects in composite beams with flexible connection
No full textSi presenta un metodo generale per l'analisi di travi composte acciaio-calcestruzzo con connessione flessibile ed effetto shear-lag in soletta. Nell'ipotesi di comportamento elastico lineare dei materiali e della connessione, si perviene ad un sistema differenziale del decimo ordine che può essere risolto in forma chiusa. I primi risultati di un'analisi numerica condotta su una trave continua a due campate mostrano l'accoppiamento esistente tra effetto shear-lag e connessione flessibile. Infine, facendo ricorso al metodo algebrizzato EM (Effective Modulus), si valuta l'evoluzione nel tempo dell'effetto shear-lag prodotta dalla viscosità del calcestruzzo
Analysis of the shear-lag effect in steel-concrete cable stayed bridges by means of deck finite elements
No full textThis paper presents the derivation of a finite element formulation for the analysis of composite decks accounting for partial interaction theory and shear-lag effects. The particularity of the proposed element, referred to as the deck finite element, relies on its ability to capture the structural response of cable stayed bridges, while preserving the ease of use of a typical line element. For these particular bridges, stress concentrations are induced in the slab by the application of concentrated forces due to the anchorage of stays. The ease of use of the proposed deck finite element is outlined considering a case study for which the calculated results have been compared against those obtained using a more refined model implemented using shell elements in a commercial finite element software
A beam finite element including shear-lag effect for the long-term analysis of steel-concrete composite decks
No full textThe paper presents a beam finite element for the long-term analysis of composite decks taking
into account the warping of the slab cross section and the partial shear interaction between the
slab and the girders. Slab shear-lag is taken into account by means of the product of a known
function, describing the shape of the slab cross section warping, and an intensity function
measuring the magnitude of warping along the beam axis. Time-dependent behaviour is
considered by means of an integral-type visco-elastic creep law for the concrete. The
numerical solution is obtained by means of the finite element method with a 13-dof beam
element and a step-by-step procedure for the evolution in time. The results of some
applications show the accuracy and the capability of the proposed element
Getto delle solette in ponti composti: confronto tra varie tecniche di frazionamento
No full textLe solette dei viadotti con impalcato continuo composto vengono usualmente realizzate con getti frazionati sulle travi metalliche non puntellate. La concomitanza delle trazioni per ritiro impedito e di quelle indotte dalle fasi costruttive può condurre alla fessurazione prematura della soletta. In questo lavoro si presenta uno studio sull’efficacia di varie tecniche di frazionamento del getto per controllare gli stati di trazione nella soletta di ponti composti a trave continua. Con riferimento ad un caso studio, vengono discussi i risultati numerici ottenuti con un programma di calcolo dedicato in grado di cogliere gli effetti dell’evoluzione della struttura e del ritiro del calcestruzzo alle brevi stagionature. L’analisi dei vari contributi considerati separatamente (peso proprio, ritiro termico, endogeno e da essiccamento) permette di comprendere i meccanismi che innescano gli stati di trazione in soletta e valutare l’efficacia dei vari sistemi costruttivi considerati
Il controllo della fessurazione negli impalcati continui a sezione composta
No full textSi presenta uno studio sul controllo della fessurazione degli impalcati composti realizzati per fasi con getto frazionato della soletta. Utilizzando un modello precedentemente proposto dagli autori si studiano diversi impalcati continui con campate di luci differenti e si analizza l’evoluzione dello stato tensionale in soletta durante la costruzione, mostrando l’efficacia dell’ottimizzazione delle sequenze di getto nella limitazione delle trazioni nella soletta e nel controllo della fessurazione a breve e a lungo termine. Si tiene conto degli effetti prodotti dal ritiro alle brevi stagionature e si mostra l’importanza della viscosità a trazione e della qualità del calcestruzzo
Creep and shear-lag coupling in steel-concrete composite beams
No full textUnder the assumption of linear viscoelastic behaviour for the concrete slab and linear elastic behaviour for the steel beam, a model for analysing the shear-lag effect in steel-concrete composite beams, is proposed. By supposing that the slab loss of planarity is described by a fixed warping function, the vertical and longitudinal displacements of the generic cross section and the intensity of the warping (shear-lag function) are assumed as unknowns of the problem. Integrating by parts the global balance condition obtained by the virtual work principle, three linear integral differential equations (expressing local equilibrium) with the relevant boundary conditions are obtained. Such a system is numerically solved by a step-by-step procedure combined with the finite differences method. Some applications on beams subjected to static actions show the practical uncoupling between creep and shear-lag
Displacement-based formulations for composite beams with longitudinal slip and vertical uplift
No full textThis paper describes three novel displacement-based formulations for the analysis of composite beams with a flexible connection which is capable of deforming along the longitudinal axis of the member as well as vertically, i.e. transverse to the interface connection. For completeness, the analytical model which forms the basis of the proposed modelling technique is presented in both its weak and strong forms. The three novel finite element formulations are derived and tested using different structural systems; their nodal freedoms include the vertical and axial displacements as well as the rotations at each element end of both layers. Curvature locking problems are observed to occur for one of these elements and the origin of this behaviour is demonstrated analytically. Two applications are then proposed adopting a bi-linear constitutive relationship for the vertical interface connection to, reflect the more realistic case in which, already in the linear-elastic range of the materials forming the cross-section and of the longitudinal interface connection, two vertical connection stiffnesses are required, i.e. one to model the event of separation between the layers and one when one bears against the other one. Copyright (c) 2005 John Wiley & Sons, Ltd
Partial Interaction Analysis With Shear-lag Effects of Composite Bridges: A Finite Element Implementation For Design Applications
No full textThis paper presents a numerical model for the analysis of composite steel-concrete beams with partial interaction to account for the deformability of the shear connection. The proposed approach is capable of capturing the structural response produced by shear-lag effects and by the time-dependent behaviour of the concrete. The versatility of the FE formulation is demonstrated for a wide range of realistic bridge arrangements, e.g. from twin-deck girders to cable-stayed bridges. The accuracy of the approach is validated against the results obtained from more refined models generated with shell elements using commercial finite element software. For each bridge typology considered, both deformations and stresses are calculated to provide greater insight into the structural performance. Particular attention is placed on the determination of the effective width to be used for design purposes and on the stress distribution induced in the concrete component, together with their variation with time due to creep and shrinkage
Time analysis of composite beams with partial interaction using available modelling techniques: A comparative study
No full textThis paper presents a comparison of available numerical structural formulations for the short- and long-term analysis of composite beams with partial shear interaction. The finite difference method, the finite element method, the direct stiffness method and the exact analytical model have been considered, and both the instantaneous analysis and the time analysis based on the age-adjusted effective modulus method (AEMM) have been carried out. For modelling based on the first two of these formulations, a spatial discretisation and a discretisation in the time domain are required, while only the time discretisation needs to be specified for the direct stiffness method. The results obtained using these formulations are compared qualitatively and their accuracy is estimated, adopting the exact analytical model as a benchmark reference with the objective of establishing the minimum spatial discretisations required to keep the error within an acceptable tolerance. These comparisons are carried out for simply supported beams, propped cantilevers and fixed ended beams, from which the qualitative behaviour of these formulations in the modelling of continuous beams can also be deduced. (c) 2005 Elsevier Ltd. All rights reserved
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