According to Earthquakes Today, around 500,000 earthquakes occur each year; 100,000 of these can actually be felt. The magnitude and destructive consequences of earthquakes have serious implications. The destruction and damage of constructed and natural environment and the loss and impairment of human life are of prime concern. A notable feature of the disaster caused by earthquakes is that harm to life is associated almost entirely with man-made structures, e.g., collapse of buildings, bridges, dams.
During an earthquake, when the ground shakes at a building site, the buildings foundations vibrate in a manner that is similar to the surrounding ground. To overcome this effect, research has spawned numerous innovations now common in earthquake engineering, including ductile detailing of concrete structures, improved connections for moment frames, base-isolation technology, energydissipation technology, and computing tools. Current research activities are focused on three areas: performance-based design, development of damageresistant systems, and improvement in the ability to predict the occurrence and intensity of earthquakes.
Our knowledge about earthquakes has advanced enormously during the past couple of decades. Corresponding advances have also been made in our understanding of the behaviour of structures, and consequently new and stringent specifications have been introduced and enforced. In this second edition, the dynamics of structures is dealt with in detail to give the book completeness. Further, with the revision of the code IS 800 in 2007, the design philosophy recommended is limit state design.
