A preliminary design formula for the strength of stiffened curved panels by design of experiment method

International audienceIn bridge construction, the use of stiffened plates for box-girder or steel beams is common day to day practice. The advantages of the stiffening from the economical and mechanical points of view are unanimously recognized. For curved steel panels, however, applications are more recent and the literature on their mechanical behaviour including the influence of stiffeners is therefore limited. Their design with actual finite element software is possible but significantly time-consuming and this reduces the number of parameters which can be investigated to optimise each panel. The present paper is thus dedicated to the development of a preliminary design formula for the determination of the ultimate strength of stiffened cylindrical steel panels. This approximate formula is developed with the help of a design of experiment method which has been adapted from the current statistical knowledge. This method is first presented, and its feasibility as well as its efficiency are illustrated through an application to the reference case of unstiffened curved panels. Then, the case of stiffened curved panels is investigated and a preliminary design formula is developed. The ease of use of this formula for preliminary design is finally illustrated in a cost optimisation problem

Modélisation des structures multicouches en analyse limite. Application au renforcement de matériau

Multilayered Structures are widely used in the field of civil engineering and construction as well as in the field of industry. One of the needs of engineers in charge for building such structures is the knowledge of their limit loads. Thus, homogenization procedures for the limit analysis of multilayered plates and beams have been developped in this work. They lead to Love-Kirchhoff and Euler-Bernoulli kinematics for the equivalent homogeneous plate and beam, respectively. In order to take into account shear effects, new multiparticular models of multilayered plate and beam have been developped and justified. After a validation of these models based on comparisons with finite element calculations, they are applied to strengthened reinforced concrete beams. A fast and easy estimation of the maximal loads is obtained for such structures and a design tool is also built.Dans le domaine du génie civil et de la construction, ainsi que de l'industrie, les structures hétérogènes multicouches sont très utilisées. L'une des demandes formulées par les ingénieurs pour concevoir de telles structures est aussi la connaissance des charges limites qu'elles peuvent supporter. Des méthodes d'homogénéisation des plaques et poutres multicouches en analyse limite ont ainsi été développées. Elles conduisent respectivement à des cinématiques de Love-Kirchhoff ou d'Euler-Bernoulli pour la structure homogène équivalente. Afin de prendre en compte les effets de cisaillement, de nouveaux modèles de plaques et de poutres multiparticulaires ont été proposés et justifiés. Après une validation par éléments finis de ces modèles, on les applique au cas des poutres en béton armé renforcées. Ils permettent d'avoir une estimation rapide des chargements maximaux supportables et de construire ainsi un outil de dimensionnement à l'Etat Limite Ultime pour de telles structures

Modélisation des structures multicouches en analyse limite (application au renforcement de matériau quasi-fragile-acier)

MARNE-LA-VALLEE-ENPC-BIBL. (774682303) / SudocSudocFranceF

Limit analysis of periodic beams

International audienceOne of the purposes of this paper is to determine G(b)(hom), the overall homogenized Euler-Bernoulli strength domain of a periodic rigid-perfectly plastic beam. It also aims at studying the relationship between the 3D and the homogenized Euler-Bernoulli beam limit analysis problems. In the homogenized beam model, the generalized 1D stresses are the axial and the flexural stress field resultants. The homogenization method suggested by [Bourgeois, S., 1997. Modelisation numerique des panneaux structuraux legers. Ph.D. thesis, University Aix-Marseille; Sab, K., 2003. Yield design of thin periodic plates by a homogenization technique and an application to masonry wall. Comptes Redus Mecanique 331, 641-646], and [Dallot, J., Sab, K., 2008a. Limit analysis of multi-layered plates. Part 1: The homogenized Love-Kirchhoff model. journal of the Mechanics and Physics of Solids 56 (2), 561-580] for periodic rigid-perfectly plastic plates is extended to periodic beams. The homogenization procedure is justified using the asymptotic expansion method. Lower and upper bounds for G(b)(hom) are provided. These bounds are analytically obtained in terms of local b axial ultimate strengths. Special cases of axially-invariant beams and laminated beams are studied and an improved upper bound is derived. Considering several sandwich beams, it is found that the discrepancy between the lower bound and the improved upper bound is small