Seismic design, general

In general, dynamic response of any system depends on the seismic excitation characteristics (both in the time and in the frequency domain). In a recent preliminary investigation of DWSSI by Tsompanakis et al. (2006), both real earthquake records and pulses were used. In the present numerical study, in order to understand more clearly various aspects of the complex phenomena incorporated in the DWSSI, the excitations were limited to harmonic and simple pulses. Results provide a clear indication of the direct dynamic interaction between a retaining wall and its retained structures. That fact justifies the necessity for a more elaborate consideration of this interrelated phenomenon on the seismic design, not only of the retaining walls, but of the nearby structures as well. 

For nuclear power plants built according to earlier standards and for many of die WWER NPPs, die seismic design basis (i.e. seismic input parameters) is generally not in accordance witii current international practice. The as-built status of NPP structures, components and distribution systems have to be checked against the site specific seismic loads in the event of an earthquake of the design basis level. 

In general, seismic design of pile foundations is evaluated by the substructure method. First, the total structure is divided into two substructure models with a convenient interface between the two at the pile cap level. Next, the stiffness matrix of the pile group, which implies soil effects, is established using the foundation substructure model or simple methods. The stiffness matrix is then implemented in the superstructure model and seismic analysis is conducted using the superstructure model to determine the demands at the interface point. Finally, capacities of individual piles are evaluated and compared to the demands by back substitution in the substructure model. For a proper determination of the seismic... 

Due to the extensive use of performance-based seismic design in earthquake engineering, nonlinear analysis has becrane an important method for evaluating the seismic performances of structures. In comparisrai with elastic analysis, nonlinear analysis is usually more complex and expensive. Nonlinear analysis generally involves... 

Seismic Design of Dams, Fig. 6 Liquefaction resistance trend curves for plastic soils, generally flatter than sands... 

The details of each safety check are given by the construction codes and therefore are not dealt with here. However, a general appreciation of the seismic design of a retaining wall is provided by the example of Fig. 9, relative to a cantilever retaining wall with a height H = 3.5 va. subjected to a seismic event characterized by a maximum acceleration = 0.25 g. Restricting the... 

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