Soil-Structure Interaction (SSI) is a critical aspect in the field of seismic response analysis, particularly within civil engineering. This phenomenon plays a vital role in understanding how structures respond to seismic events, especially when they are situated on varying types of soil. The analysis of SSI becomes increasingly important when dealing with heavy and rigid structures, such as Nuclear Power Plants (NPPs), which may be constructed on medium or soft soil sites.

In this enlightening book published by Bokforlaget Efron & Dotter AB, the author delves into the intricacies of SSI and its implications for seismic analysis. The discussion begins with the traditional approach where seismologists describe seismic excitation based on the seismic motion observed at specific control points on the surface of the site. The fundamental question arises: does the same point in the structure exhibit the same seismic response motion during identical seismic events? If the answer is affirmative, then the seismic motion from seismologists can be directly applied to the base of the structure in what is known as ‘fixed-base analysis.’ This traditional viewpoint suggests that ‘no SSI occurs,’ although it is important to note that soil does influence the structure’s movement, indicating that interaction is always present.

However, the scenario drastically changes when a structure is heavy and rigid, and especially when it is embedded within the soil. Such structures significantly alter the seismic response of the soil compared to the original free-field conditions. This alteration is particularly relevant for structures like NPPs, which require detailed consideration of SSI effects due to their unique design and operational parameters.

The book thoroughly explores various approaches to SSI analysis, highlighting different SSI effects that may arise depending on the context and conditions of the site. A key focus is placed on the Combined Asymptotic Method (CAM), a technique developed by the author, which has been notably utilized in the design of NPPs located in seismic regions. This method offers insights into how to effectively analyze and design structures that are not only resilient to seismic forces but also incorporate the dynamic interaction with the underlying soil.

Moreover, as civil structures increasingly exhibit characteristics similar to those of NPPs, such as comparable masses and degrees of embedment, the methodologies discussed in this book are becoming increasingly relevant for civil structural engineers. By understanding the principles of SSI, engineers can better predict the behavior of structures during seismic events, thereby enhancing safety and performance.

In summary, this comprehensive exploration of soil-structure interaction provides both theoretical insights and practical applications for engineers. By integrating these concepts into their workflows, civil engineers can significantly enhance the structural integrity and safety of buildings and infrastructure in seismic zones.