John Lysmer

Soil-structure interaction analyses by finite elements — State of the art

Abstract In this paper the authors have attempted to summarize the current capability for evaluating soil-structure interaction effects during earthquakes using finite element procedures. A concise summary of methods available, together with their capabilities and relative costs is presented. It is suggested that finite element procedures provide a powerful tool for use in the design of nuclear plants, especially for embedded structures, and their applicability in this respect is illustrated by comparing computed results with those recorded in a nuclear plant during a strong motion earthquake. It is concluded that when the methods are used in conjunction with good engineering judgment and with full recognition of their limitations, they provide evaluations of response with a level of accuracy entirely adequate for engineering design.

Dynamic behaviour of tunnels under impact loads

Abstract Safety related structures of a nuclear power plant are often required to withstand the effects of an aircraft impact load. Underground tunnels, carrying cables and pipes between buildings, also belong to this class of structures. For the design of components located inside the tunnels one must know the response of the structure of the connection points of the components. Acceleration response spectra and relative displacements are of major interest. Using finite element techniques in order to idealize the tunnel and the surrounding soil the effects of the various parameters on the dynamic response of the tunnels are investigated. It is found that some of the main parameters which influence the dynamic response of a tunnel are: soil stiffness and layering, depth of embedment and the thickness of the concrete, protective slab. Vertical accelerations are also affected by the stiffness of the tunnel.