Seismic Analysis of Structures by T. K. Datta

Seismic Analysis of Structures by T. K. Datta
Seismic Analysis of Structures by T. K. Datta


For structural engineers, earthquake engineering can be broadly divided into three areas, namely, seismology (including ground effects), seismic analysis, and seismic design. These areas are big subjects in themselves and deserve separate treatment in exclusive books. While there are many excellent books that cover these three areas in varying proportions, none have been written exclusively on the seismic analysis of structures for use in teaching an undergraduate elective or a postgraduate core course. Furthermore, there are virtually no books that contain all aspects of the seismic analysis of structures, combining new concepts with existing ones, which graduate students pursuing research in the area of earthquake engineering would appreciate. Considering these major requirements, the present book has been written despite the fact that a number of masterly textbooks on structural dynamics and earthquake engineering, dynamics of soil structure interaction, and geotechnical earthquake engineering are already available within the earthquake engineering community, and where many of the theoretical concepts presented here have been covered more elaborately. The present book attempts to provide textbook material for the learning and teaching of the seismic analysis of structures in totality.

Seismic Analysis of Structures by T. K. Datta
Seismic Analysis of Structures by T. K. Datta

It offers a comprehensive and unique treatment of all aspects of the seismic analysis of structures, starting with seismology and through to the seismic control of structures. The materials in the book are arranged and presented in a manner that is expected to be equally useful to both undergraduate and postgraduate students, researchers, and practicing engineers. Depending on the particular requirements, it is possible to structure courses at various levels on different aspects of seismic analysis based on the contents of this book. It is presumed that the readers have some background of structural dynamics, preferably having undergone a basic course in structural dynamics. The book is presented in nine chapters. The first chapter,Seismology, deals with the fundamentals of seismology that a structural engineer must know. The chapter deals with topics such as the earth and its interior, plate tectonics, causes of earthquakes, seismic waves, earthquake measurement parameters, the measurement of earthquakes, modification of earthquake waves due to the nature of the soil, and seismic hazard analysis.

The last topic describes both deterministic and probabilistic seismic hazard analyses, and seismic risk at a site. The concept of microzonation based on hazard analysis is also included. The second chapter,Seismic Inputs for Structures, provides an extensive coverage of the various types of seismic inputs used for different types of seismic analysis. The seismic inputs discussed include time history records and their frequency contents, power spectral density function (PSDF) of ground motion, different types of earthquake spectra, design response spectra, probabilistic response spectra, site specific spectra, and uniform hazard spectra.

Generation of the time histories of synthetic ground motion from a response spectrum and the PSDF of ground motion is also briefly discussed. Finally, predictive relationships for different seismic input parameters such as peak ground acceleration (PGA), response spectra, PSDFs, modulating functions, and coherence functions are given.

The third chapter,Response Analysis for Specified Ground Motions, deals with different methods of analysis of single and multi-degrees of freedom systems for specified time histories of ground motion. Methods include time domain analysis, frequency domain analysis using fast Fourier transform (FFT), modal time domain, and frequencydomain analyses for both single-point and multi-point excitations.Methods of analysis are described for both second-order and state-space equations.

The mode acceleration method is also presented. At the end of the chapter, steps for developing a comprehensive program using MATLAB  are outlined, which can solve single and multi-degrees of freedom systems for a specified time history of ground motion using all of the methods of analysis discussed in the chapter. In addition, use of the SIMULINK toolbox of MATLAB to solve problems is also demonstrated. The fourth chapter,Frequency Domain Spectral Analysis, introduces the concept of spectral analysis of structures, treating the ground motion as a stationary random process and deals with the subject in a manner that does not require an in-depth knowledge of the theory of random vibration. Using FFT, the fundamentals of frequency domain spectral analysis are introduced, and then the required concepts of autocorrelation, cross correlation, power spectral density functions, and so on, are presented.

The basic relationship between multi-point input and output PSDFs of a structural system is given using a matrix formulation. Direct and modal spectral analyses are described for single-point and multi-point excitations. Furthermore, a method for the determination of the mean peak response from a spectral analysis is outlined. The fifth chapter,Response Spectrum Method of Analysis, discusses the response spectrum method of analysis for single- and multi-point excitations of multi-degrees of freedom systems. Development of the methods is presented after a brief background of the concept of equivalent lateral load. The necessary explanation for including the effect of spatial correlation for multi-point excitation is duly incorporated in the theory. Other topics discussed in this chapter include modal combination rules, the response spectrum method of analysis for none classically damped systems and secondary systems, the base shear approach, and comparison between the code provisions of a few codes in relation to the base shear and response spectrum methods of analysis.

The sixth chapter,Inelastic Seismic Response of Structures, covers the methods of inelastic response analysis of structures and the fundamental aspects of inelastic behavior of structural components for earthquake forces. The topics include the hysteretic behavior of materials, the incremental method of analysis of single- and multi-degrees of freedom systems accounting for the hysteretic effects, the incremental analysis procedure with bidirectional interaction, pushover analysis, ductility demand, inelastic response spectra, and ductility in multi-storey buildings. The first part of the seventh chapter onSeismic Soil Structure Interaction, provides the background to seismic wave propagation through the soil medium and gives the finite element analysis of the wave propagation problem. Next, the dynamic soil–structure interaction is presented by explaining kinematic interaction, inertial interaction, and the direct and multi-step method for bounded problems. Both the finite element method and the substructure technique for solving soil–structure and soil–pile structure interaction problems are described.

The topics include time domain and frequency domain analyses using direct, substructure, and modal analysis techniques for single- and multi-point excitations, analyses for soil–pile structure interaction problems, and underground structures. The eighth chapter,Seismic Reliability Analysis of Structures, deals with the seismic reliability analysis of structures in which the basic concept of reliability analysis is introduced first, followed by some popularly used techniques such as the first order second moment (FOSM) method, the Hasofer–Lind method, the second-order method, and a simulation based method for solving the reliability problems. Uncertainties involved in the seismic reliability analysis of structures are then elaborated, and a number of seismic reliability analysis techniques are presented.

They include reliability analysis for threshold crossing, the first passage failure of structures, risk assessment using a damage probability matrix, and approximate probabilistic risk assessment of structures.

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