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Abstract: This paper proposes a new algorithm for modeling the nonlinear seismic behavior of fractured concrete gravity dams considering dam–reservoir interaction effects. In this algorithm, the cracked concrete gravity dam is modeled by distinct element (DE) method, which has been widely used for the analysis of blocky media. Dynamic response of the reservoir is obtained using boundary element (BE) method. Formulation and various computational aspects of the proposed staggered hybrid approach are thoroughly discussed. To the authors'' knowledge, this is the first study of a hybrid DE–BE approach for seismic analysis of cracked gravity dam–reservoir systems. The validity of the algorithm is discussed by developing a two-dimensional computer code and comparing results obtained from the proposed hybrid DE–BE approach with those reported in the literature. For this purpose, a few problems of seismic excitations in frequency- and time-domains, are presented using the proposed approach. Present results agree well with the results from other numerical methods. Furthermore, the cracked Koyna Dam is analyzed, including dam–reservoir interaction effects with focus on the nonlinear behavior due to its top profile crack. Results of the present study are compared to available results in the literature in which the dam–reservoir interaction were simplified by added masses. It is shown that the nonlinear analysis that includes dam–reservoir interaction gives downstream sliding and rocking response patterns that are somehow different from that of the case when the dam–reservoir interaction is approximated employing added masses. [Copyright &y& Elsevier]

Abstract: System identification is an emerging field of structural engineering which plays a key role in structures of great importance such as concrete gravity dams. In this study, an artificial neural network (ANN) procedure is proposed for the identification of concrete gravity dams, in conjunction with a hybrid finite element–boundary element (FE–BE) analysis for the prediction of dynamic characteristics of an existing concrete gravity dam with an empty reservoir. First, a dam–reservoir interaction analysis is carried out by the hybrid FE–BE approach in the frequency domain. A two-dimensional (2D) FE model (FEM) is used for linear-elastic analysis of the gravity dam on a rigid foundation, while the unbounded reservoir with inviscid, compressible, and frictionless fluid is discretized by BEs. Various analyses are performed for different height to base width ratios of dams in terms of different wave reflection coefficient of the reservoir bottom. The use of ANNs is motivated by the approximate concepts inherent in system identification approaches, and the time-consuming repeated analyses required for dam–reservoir interacting systems. The conjugate gradient algorithm (CGA) and the Levenberg–Marquardt algorithm (LMA) are implemented for training the ANNs, using available data generated from the results of coupled dam–reservoir system analyses. The trained ANNs are then employed to compute the dynamic amplification of dam crest displacement and natural frequencies of existing concrete gravity dams through forced vibration tests. The results obtained by solving the present inverse problem are compared with existing FEM solutions to demonstrate the accuracy and efficiency of the proposed method. [ABSTRACT FROM AUTHOR]