Structural Dynamics and Earthquake Engineering

Vibrations in structural systems may result from a wide variety of sources. Some of the most common and significant of dynamic loads imposed on structures are those caused by environmental conditions such as wind earthquakes and water waves. Of these environmental sources, earthquake appears as the most important in terms of their enormous potential for damage to structures and loss of human life. In addition, earthquakes are responsible for hundreds of millions of dollars in property damage annually.

• Structural dynamics is a type of structural analysis which covers the behavior of a structure subjected to dynamic loading. Dynamic loads include people, wind, waves, traffic, earthquakes and blasts. Any structure can be subjected to dynamic loading.

A dynamic load is any load of which its magnitude, direction, and/or position varies with time. Dynamic load can be caused by Initial conditions, Applied forces or Support motion.

For structural engineers, earthquake engineering can be broadly divided into three areas, namely: seismology, seismic analysis, and seismic design.

-Seismology: The study of seismic sources (mostly earthquakes), the waves they produce and the properties of the media through which these waves travel. It is primarily an observational science. Quantitative measurements of seismic ground motion of as a function of time require physically well defined, continuously recording instruments.

An earthquake is a sudden and transient motion of the earth’s surface (vibrations of earth’s surface caused by waves emanating from a source of disturbance inside the earth).

The internal structure of the Earth is one of the key parameters to understand the major seismic activity around the world. The Earth may be considered to have three concentric layers: The innermost part of the Earth is the core and it is mainly composed of iron. The core has two separate parts: the inner core and outer core. The inner core is solid and the outer core is liquid.