Earthquake Engineering for Structural Design

Abstract

Earthquakes were the cause of more than 1.5 million deaths worldwide during the 20th Century. During the beginning of the 21st Century the number of deaths was about half a million. This is an unacceptable finding, because earthquakes can no longer be regarded as natural disasters, since the main cause of this huge number of casualties is the inadequate seismic resistance of the building stock, lifelines and industry, which could be avoided. Earthquakes do not kill people, but the building collapse can do it. It is an unbelievable situation that, after a century of research works, each strong earthquake brings new surprises and creates the situation that new lessons have to be learnt. After a series of devastating earthquakes during the last years of the past century (1994 Northridge, 1995 Kobe, 1999 Kocaeli and Taiwan earthquakes), it has been recognized by society that both seismic hazard and risk have to be reassessed. Important progress was made in the last period, but many problems remain unsatisfactorily solved. Therefore, now is the right moment to analyze the level of current knowledge and to identify the challenges for future research works and for the next code generation. This is the main intention of this book. The progress in understanding and controlling the complex phenomena of the earthquake production can be analyzed both from scientific and practical points of view. From the scientific point of view, the main effort must be directed towards the inner understanding of the complex phenomenon of an earthquake. Some new fundamental disciplines, developed in the last decades, must be deeply studied. The most important among them is the Earth Science, which explores the different processes and transformations produced in the evolution of the Earth and looks at how it is likely to evolve in the future. The Earth Science, more than any other science, is the embodiment of the emerging new sciences, where the focus is on Complex Non-linear Systems: Evolutionary and Self-Organized Dissipative Systems, Bifurcation, Catastrophes and Chaos Theories. The Earth surface can be considered as a complex of self-organized systems, consisting in tectonic plates and mantle, the equilibrium being assured by the mantle convection. The earthquakes represent a sudden destruction of this equilibrium. Considering the Chaos Theory, an essential discipline for Complex Non-linear Systems, which underlines the importance of small perturbation in the initial conditions (Butterfly effect), it is possible to understand the great difficulties in the prediction of the characteristics of the next earthquakes. These aspects show the limits of the probabilistic analysis in case of earthquake. Due to small differences in the initial conditions, for the same source, each new event is very different from the already