Modal analysis of concrete arch dam–reservoir–massed foundation system in frequency domain

Abstract

Modal analysis of concrete arch dam–reservoir–foundation rock systems is a challenging task. The complexities arise mainly due to computing mode shapes encountered when solving an eigenvalue problem with asymmetric generalized mass and stiffness matrices. Moreover, the problem becomes complicated when wave propagation is occurring due to the inclusion of water compressibility and foundation rock mass. In the present study, a computational tool is especially developed for this purpose. The theoretical background is explained initially. Subsequently, dynamic analysis of the Morrow Point arch dam–reservoir–foundation rock system is carried out with different values of reservoir bottom absorption coefficient. In addition, some of the modal characteristics of such systems, including resonant frequencies and natural periods, are discussed. The main objective is to perform these analyses by modal analysis. However, the direct method of analysis is also carried out in each case as a basis for comparison from the perspectives of accuracy and efficiency.