The high performance requirements current seismic regulations impose for concrete dams requires the adoption of dynamic analysis methods that allow the structural response of dams to earthquakes to be represented accurately and as close to reality as possible, reducing as much as possible the excessive conservatism of the results derived from simplified approaches. In the modelling of structural dam-basin-foundation systems affected by seismic events, it is in particular necessary to limit the analysis to a calculation domain that is relatively small compared to its real extension, by introducing artificial boundaries that are able to ideally reproduce, within the calculation domain, the same behaviour that would be obtained with the unlimited foundation. These artificial boundaries (known as absorbent or non-reflecting boundaries) must allow the entry of seismic waves into the foundation as well as the exit from the foundation of waves originating from the presence of the dam-basin system.

Among the various approaches available in the technical literature, a model for the propagation of seismic waves has been adopted that uses boundaries consisting of springs and dampers and applies the seismic action by means of equivalent seismic forces acting on the boundaries of the foundation. The spring and damper elements available in the Abaqus finite element code have been used operationally, and the equivalent seismic forces to be applied to the boundaries of the foundation were calculated according to a procedure documented in the literature and based on the theoretical solution of the problem of vertical propagation of waves in an elastic half-space.

With the aim of efficiently using the seismic wave propagation model in the numerical analysis of real problems, specific pre-processing tools capable of automating the calculation of equivalent seismic forces were developed and validated. The adopted model was also applied to the case study of the highest non-overflow monolith of the Pine Flat gravity dam (USA), proposed as Theme A of the 15th ICOLD International Benchmark Workshop on Numerical Analysis of Dams to continue the investigations undertaken in the USSD Workshop on Evaluation of Numerical Models and Input Parameters in the Analysis of Concrete Dams held in 2018.