Modern Earthquake Engineering
Earthquakes are among the most destructive natural disasters on our planet. Over history, enormousengineering and research efforts have been devoted to the study of causes and consequences of earthquakes, the prediction and forecasting of future earthquakes, the determination of ground motion intensities in a particular site, and the seismic response assessment and the mitigation measures for various types of structures and foundations. All these efforts have been intended simply to keep
structures and their contents from falling down and causing damage and to keep people safe during earthquakes.
During the last century, through a synergy of various pieces of know-how associated with the contents above, a unique scientific topic, earthquake engineering, has finally been formed. It is essentially focused on finding solutions to problems posed by seismic hazards.
During its development, earthquake engineering has borrowed much from other engineering disciplines in its understanding of seismic wave propagations and ground motion characteristics, in considering nonlinear soil and structural responses and engineering dynamics, and in developing probability-based design approaches. Although earthquake engineering as a scientific topic is by no means fully understood (and perhaps never will be), the great amount of activity in this field has made it possible to form a practical subject in a fairly systematic, coherent, and quantitative manner.
The development of modern earthquake engineering has been closely linked to advances in computer technology, allowing engineers to solve problems of increasing complexity in two aspects: First, it allows for the calculation of results based on classical solutions but with numerical evaluation of certain terms that cannot be expressed in a closed form; second, it also allows for the modeling of complex systems (structures, foundations, soils, or faults) using approximation methods such as finite element method and to perform numerical calculations to obtain the system’s response. However, even though engineers and researchers are using computers to solve many seismic problems with great complexity, many of them lack an actual understanding of the essential principles in earthquake engineering, and their capability to properly evaluate seismic ground motions and structural responses is thus limited and even weaker than that of those working on this subject decades ago. This is also partly because the complexity of the analyzed seismic problems has dramatically increased in recent decades, which is more case-dependent, and therefore, less general conclusions can be drawn.
Eventually, this has led to many engineers and researchers losing the “big picture” and intuition toward original problems and principles. Moreover, the division of responsibilities between seismologists and civil engineers has become more “clear,” thus “eliminating the previously critical need for engineers to get involved ‘up front’ in the seismic input characterization for a project” (CA Cornell). In many cases, professional structural and geotechnical engineers are not able to qualify the seismic input ground motions with respect to their seismological features, and
seismologists and geotechnical and structural engineers often understand each other only poorly. Furthermore, students who study earthquake engineering are given canned class exercises and deterministic projects, which are often far different from the real-world seismic engineering problems that have a great diversity in various aspects. Therefore, in spite of increased knowledge on earthquake engineering, the problems of seismic design are in many cases handled without success despite large
expenditures of investment. This leads to an insurmountable barrier to efficiently manage the risk of structures and to further improve the design, potentially posing a significant safety hazard, and may also result in significant economic loss. Such considerations motivated me to write this book.
The objective of this book is to offer a methodical presentation of essentials of earthquake engineering, based on “understandable” mathematics and mechanics with an emphasis on engineering application aspects; to present the most useful methods for determining seismic ground motions and loading on structures; to apply both the well-accepted and emerging methods to perform seismic design and analysis for real-world engineering structures; and to implement various types of mitigation measures to increase the seismic resistance of structures. Instead of being generic, the book is filled with concrete explanations from real-world ngineering practices.
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