Effects of fluid–structure interaction modeling assumptions on seismic floor acceleration demands within gravity dams

This paper presents an original investigation of the sensitivity of floor acceleration demands in gravity dams to various modeling assumptions of the impounded reservoir. Such floor acceleration demands are crucial for the assessment of the seismic performance or vulnerability of dam-supported appurtenant structures. Two approaches are proposed to obtain floor acceleration demands: analytical and coupled dam–reservoir finite element models. Both techniques are applied to typical dam–reservoir systems with different geometries. The dam–reservoir systems are subjected to ground motions with various frequency contents and the resulting floor acceleration demands are examined to investigate the effects of reservoir geometry, water compressibility, reservoir bottom wave absorption and dam higher vibration modes. A new approach based on proposed floor frequency response functions is also developed to assess floor acceleration demands at the stage of preliminary seismic design or safety evaluation of dam-supported appurtenant structures. Examples are given to illustrate how the proposed approach can be effectively used to compare floor acceleration demands within different dams or within the same dam considering various modeling assumptions of the reservoir.