Earthquake engineering is an interdisciplinary branch of engineering that designs and analyzes structures, such as buildings and bridges, with earthquakes in mind. Its overall goal is to make such structures more resistant to earthquakes. An earthquake (or seismic) engineer aims to construct structures that will not be damaged in minor shaking and will avoid serious damage or collapse in a major earthquake. Earthquake engineering is the scientific field concerned with protecting society, the natural environment, and the man-made environment from earthquakes by limiting the seismic risk to socio-economically acceptable levels. Traditionally, it has been narrowly defined as the study of the behavior of structures and geo-structures subject to seismic loading; it is considered as a subset of structural engineering, geotechnical engineering, mechanical engineering, chemical engineering, applied physics, etc. However, the tremendous costs experienced in recent earthquakes have led to an expansion of its scope to encompass disciplines from the wider field of civil engineering, mechanical engineering and from the social sciences, especially sociology, political science, economics and finance.
Definition of Earthquake Engineering:
An earthquake is a sudden slipping or movement of a portion of the Earth's crust or plates, caused by a sudden release of stresses. Earthquake epicenters are usually less than 25 miles below the Earth's surface and are accompanied and followed by a series of vibrations.
What causes earthquakes and where do earthquakes happen
The earth has four major layers: The inner core, outer core, mantle and crust. The crust and the top of the mantle make up a thin layer on the surface of earth. But this layer is not a single cover, it is made up of many pieces like jigsaw covering the surface of the earth. These keep slowly moving around each other, slidepast one another and bump into each other. These puzzle pieces are called tectonic plates, and the edges of the plates are called the plate boundaries. The plate boundaries are made up of many faults, and most of the earthquakes around the world occur on these faults. Since the edges of the plates are rough, they get stuck while the rest of the plate keeps moving. Finally, when the plate has moved far enough, the edges unstick on one of the faults and there is an earthquake.
Types of earthquakes
Most earthquakes in the world occur along the boundaries of the tectonic plates and are called Inter-plate Earthquakes. A number of earthquakes also occur within the plate itself away from the plate boundaries, called Intra-plate Earthquakes.
How are earthquakes recorded
Earthquakes are recorded by instrument called seismographs. The recording they made, is called a seismogram. The seismo gram consists of two parts, a base and a weight, to held it firmly in the ground. When an earthquake causes the ground to shake, the base of the seismograph shakes too, but the hanging weight does not. Instead the spring or string that it is hanging from absorbs all the movement. Thus the difference between the moving and immovable part is recorded.
How are earthquakes measured??
The size of an earthquake depends on the size of the fault and the amount of slip on the fault, but this cannot be measured directly as faults are deep in the earth. The seismogram recordings made on the seismographs at the surface of the earth are used to determine the intensity of earthquake. A short line with less zigzag portions represents a small earthquake and a lengthy line with a lot of zigzag sections shows a large earthquake. The length of line on the seismograph depends on the size of the fault and the wigginess of the line depends upon the amount of slip of the fault. The size or intensity of earthquake is called Magnitude of earthquake.
Purpose and background of earthquake engineering
With the introduction of ASCE 7-02 Minimum Load Standards and the 2003 International Building Code (IBC), some consideration of seismic resistant design is required for most building structures in the United States. Effective use of these documents requires a thorough understanding of the principles of earthquake engineering, from ground motion seismology, to structural dynamics, to inelastic behavior, to design and detailing. understanding to practicing professional engineers that have little or no previous training in earthquake engineering. While other seismic seminars focus on the design aspect of earthquake engineering, the purpose of this seminar is to concentrate on the fundamentals. The course begins with a historical and philosophical review of earthquake engineering and seismic code development, followed by an overview of the latest code approaches to seismic resistant design. These code approaches are then broken down into their basic components, and a detailed step-by-step explanation is provided on how and why each component was developed. The seminar includes a description of a variety of seismic resistant structural systems in reinforced concrete and structural steel. The seminar ends with a brief look towards the future: passive energy systems, seismic isolation, and performance based concepts in earthquake engineering. Whenever possible, the material is taught by example. The powerful NONLIN computer program, developed by FEMA for earthquake engineering education, serves a prominent role during the first day of the course. To maximize your ability to continue to learn about earthquake engineering, detailed reference material is provided for each slide presented in the seminar. The course also gives you the latest information on earthquake engineering materials available on the world wide web.
Aims and Objectives of earthquake engineering study
The main objective of this volume is to illustrate to students of structural and architectural engineering the problems and solutions in attaining efficient earthquake-resistant structures and facilities. To achieve this objective, after a brief discussion of the general goals in seismic-resistant design and construction of structures and facilities, the different sources of damage that can be triggered by an earthquake are discussed and illustrated.
Emphasis is placed on the discussion and illustration of damage induced by vibration on timber, masonry, concrete and steel structures. The importance of a comprehensive approach to the problem of earthquake resistant construction is emphasized next and the need for placing more emphasis on conceptual design is discussed by offering guidelines for and illustrations of efficient seismic-resistant design. The need for research in earthquake-resistant design and construction is briefly discussed and examples of integrated experimental and analytical investigations in the development of modern seismic-resistant design are also shown.
What earthquake engineer should study / know
- Geotechnical earthquake engineering
- Performance-based seismic engineering
- Disaster planning
- Earthquake resistant design and analysis
- Engineering seismology
- Risk and reliability seismic engineering
- Soil dynamics
- Structural dynamics
Recommended books and softwares
Steven L. Kramer. Geotechnical Earthquake Engineering. Prentice Hall, 1996. ISBN: 0133749436 Software and Computer tools to be used Many of the problems in this course will require numerical solutions. Matlab, MathCAD or similar softwares and environments will be used for such purpose. Examples of numerical exercises will be spectral analysis using FFT, Response Spectra, and so on. SHAKE will be used for 1-D ground response analysis.