Fundamentals of Earthquake Engineering

From Source to Fragility

Amr S. Elnashai, Luigi Di Sarno

• Publisher: Wiley
• Year: 2015
• ISBN:
  9781118700471
• Edition: 2
• Topic: Physical Sciences
• Subtopic: Mechanics

Fundamentals of Earthquake Engineering: From Source to Fragility, Second Edition combines aspects of engineering seismology, structural and geotechnical earthquake engineering to assemble the vital components required for a deep understanding of response of structures to earthquake ground motion, from the seismic source to the evaluation of actions and deformation required for design, and culminating with probabilistic fragility analysis that applies to individual as well as groups of buildings. Basic concepts for accounting for the effects of soil-structure interaction effects in seismic design and assessment are also provided in this second edition.

The nature of earthquake risk assessment is inherently multi-disciplinary. Whereas this book addresses only structural safety assessment and design, the problem is cast in its appropriate context by relating structural damage states to societal consequences and expectations, through the fundamental response quantities of stiffness, strength and ductility.

This new edition includes material on the nature of earthquake sources and mechanisms, various methods for the characterization of earthquake input motion, effects of soil-structure interaction, damage observed in reconnaissance missions, modeling of structures for the purposes of response simulation, definition of performance limit states, fragility relationships derivation, features and effects of underlying soil, structural and architectural systems for optimal seismic response, and action and deformation quantities suitable for design.

Key features:

• Unified and novel approach: from source to fragility
• Clear conceptual framework for structural response analysis, earthquake input characterization, modelling of soil-structure interaction and derivation of fragility functions
• Theory and relevant practical applications are merged within each chapter
• Contains a new chapter on the derivation of fragility
• Accompanied by a website containing illustrative slides, problems with solutions and worked-through examples

Fundamentals of Earthquake Engineering: From Source to Fragility, Second Edition is designed to support graduate teaching and learning, introduce practising structural and geotechnical engineers to earthquake analysis and design problems, as well as being a reference book for further studies.

1
Earthquake Characteristics

1.1 Causes of Earthquakes

1.1.1 Plate Tectonics Theory

An earthquake is manifested as ground shaking caused by the sudden release of energy in the Earth’s crust. This energy may originate from different sources, such as dislocations of the crust, volcanic eruptions or even by man-made explosions or the collapse of underground cavities, such as mines or karsts. Thus, while earthquakes are defined as natural disturbances, different types of earthquake exist: fault rupture-induced, volcanic, mining-induced and large reservoir-induced. Richter (1958) has provided a list of major earth disturbances recorded by seismographs as shown in Figure 1.1. Tectonic earthquakes are of particular interest to the structural engineers, and further discussion will therefore focus on the latter type of ground disturbance.

Figure 1.1 Earth disturbances recorded by seismographs.

Earthquake occurrence may be explained by the theory of large-scale tectonic processes, referred to as ‘plate tectonics’. The theory of plate tectonics derives from the theory of continental drift and sea-floor spreading. Understanding the relationship between geophysics, the geology of a particular region and seismic activity began only at the end of the nineteenth century (Udias, 1999). Earthquakes are now recognised to be the symptoms of active tectonic movements (Scholz, 1990). This is confirmed by the observation that intense seismic activity occurs predominantly on known plate boundaries as shown in Figure 1.2.

Figure 1.2 Tectonic plates (a) and worldwide earthquake distribution (b).

(Adapted from Saint Louis University, Earthquake Center, USA.)

Plates are large and stable rigid rock slabs with a thickness of about 100 km forming the crust or lithosphere and part of the upper mantle of the Earth. The crust is the outer rock layer with an internal complex geological structure and a non-uniform thickness of 25–60 km under continents and 4–6 km under oceans. The mantle is the portion of the Earth’s interior below the crust, extending from a depth of about 30 km to about 2900 km; it consists of dense silicate rocks. The lithosphere moves differentially on the underlying asthenosphere, which is a softer warmer layer around 400 km thick at a depth of about 50 km in the upper mantle. It is characterised by plastic or viscous flow. The horizontal movement of the lithosphere is caused by convection currents in the mantle; the velocity of the movement is about 1–10 cm/year. Current plate movement can be tracked directly by means of reliable space-based geodetic measurements, such as very long baseline interferometry, satellite laser ranging and global positioning systems.

Large tectonic forces take place at the plate edges due to the relative movement of the lithosphere–asthenosphere complex. These forces instigate physical and chemical changes and affect the geology of the adjoining plates. However, only the lithosphere has the strength and the brittle behaviour to fracture, thus causing an earthquake.

According to the theory of continental drift, the lithosphere is divided into 15 rigid plates, including continental and oceanic crusts. The plate boundaries, where earthquakes frequently occur, are also called ‘seismic belts’ (Kanai, 1983). The Circum-Pacific and Eurasian (or Alpine) belts are the most seismically active. The fo...

Table of contents

• Cover
• Title page
• Table of Contents
• Preface
• Foreword
• Acknowledgements
• Introduction
• List of Abbreviations
• List of Symbols
• 1 Earthquake Characteristics
• 2 Response of Structures
• 3 Earthquake Input Motion
• 4 Response Evaluation
• 5 Fragility Relationships for Structures
• 6 Seismic Soil–Structure Interaction
• Concluding Remarks
• Appendix A
• Appendix B
• Index
• End User License Agreement