e seismic assessment of a secondary structure of the Chancy-Pougny dam, namely, the upper bridge, is discussed in this paper. A first seismic assessment, performed according to classical force-based methodology, concluded the necessity of an extensive retrofitting for the upper bridge. By contrast, the application of the displacement-based approach showed that the current situation is already satisfactory, and therefore, practically no retrofitting is needed. e paper focuses on the nonlinear timehistory analyses which were achieved in order to check the accuracy of the results obtained using the displacement-based method.e structural characteristics of the reinforced concrete upper bridge are similar to those of conventional bridges. However, the piers were built with very little reinforcement and consequently they will exhibit a rocking behavior in case of earthquake loading. Rocking is rather a favorable failure mechanism and is related to a certain amount of displacement capacity. However, this behavior is not linked to plastic energy dissipation which may significantly increase the related displacement demand. In order to determine the real displacement demand, nonlinear time-history analyses were achieved with SDOF systems defined by an "S" shape hysteretic model. Spectrum compatible stationary synthetic accelerograms and slightly modified recorded earthquakes were both used for acceleration time-histories. e results showed that the displacement demand corresponds well with the one determined by usual push-over analysis. e results show a very favorable seismic situation, related to a relatively stiff structure associated to rock soil conditions with an A class soil. e seismic safety of the upper bridge is already satisfactory for the current state (without retrofitting). Consequently, the proposed costly reinforcement for the upper bridge could be significantly reduced.

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a MAPS Diffusion SA , 1052, Le Mont-sur-Lausanne, Suisse b IBAP-Béton armé et précontraint, EPFL , 1015, ** IBAP-Bgton arm6 et prkcontraint, EPFL, 1015 Luusanne, Suisse RESUME. Cet article dicrit les bases tht?oriques d'un algorithme de calcul destine a l'analyse des effets de la fissuration et du fluage sur les constructions en biton armi et pricontraint. Lhlgonthme permet essentiellement de privoir le degri de fissuration et les diformations a long terme de l'ouvrage. Des exemples purement acadimiques et d'autres exemples correspondant a des ouvrages concrets, dont le comportement a i t i analysi en mettant en auvre l'algorithme proposi, sont don& a titre d'illustrations. A B~~R A C T . This article purpose is to describe theoretical basis of a algorithm for analysis of cracking and creep effect on reinforced and prestressed concrete structures. The algorithm allows essentially to anticipate work cracking degree and long term displacement. Purely academical examples as well a examples corresponding to real structures. the behavior of which has been analysed by mean of the proposed algorithm. are given as illustrations. MOTS-CLES : loi moment-courbure du CEB, participation du biton tendu. rigiditi riduite, difonnation a long tenne, fissuration.

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