Introduction to Dynamics of Structures and Earthquake Engineering

Part I Dynamics of Structures 1 Introduction 1.1 Idealization of the structures 1.2 Degrees of freedom 1.3 Stiffness 1.4 Mass 1.5 Damping 1.6 Equations of motion 1.6.1 Free vibrations 1.6.2 External excitations 2 SDOF Systems 2.1 Linear SDOF Systems 2.1.1 Free vibrations 2.2 Response to harmonic excitations 2.2.1 Undamped systems 2.2.2 Viscously damped systems 2.3 Response to an impulsive excitation 2.4 Response to a periodic excitation 2.5 Earthquake response 2.6 Transmissibility function 2.7 Nonlinear system response 3 Methods of solution of the equation of motion 3.1 Analytical methods 3.2 Duhamel's integral 3.3 Fourier series 3.4 Numerical methods 3.4.1 Explicit methods 3.4.2 Implicit methods xiii xiv Contents 3.4.3 Comparison between the different numerical methods 3.4.4 Numerical methods for nonlinear problems 4 MDOF systems 4.1 Discretization 4.2 Shear Type and Bending Type Frames 4.3 Mass, Stiffness and Damping Matrix 4.3.1 Bending Type Frames 4.3.2 Shear Type Frames 4.4 Reduction of DOFs 4.5 Modal Analysis 4.5.1 Vibrational Modes Response 4.5.2 Modal Expansion Of Displacements 4.5.3 Energetic Considerations 4.6 Free Vibrations 4.6.1 Undamped Systems 4.6.2 Damped Systems 4.7 Response to Harmonic Excitation 4.7.1 Undamped Systems 4.7.2 Viscously Damped Systems 4.8 Earthquake response 4.8.1 Numerical example 4.9 3D MDOF multistory buildings 5 Energy dissipation 5.1 Damping energy 5.2 Plastic energy 6 Damping on structures 7 Distributed mass and elasticity systems 7.1 Vibrational Modes Analysis 7.2 Vibrational Modes Analysis of Forced Systems 8 Generalized SDOF systems 8.1 Lagrangian approach 8.2 Approximated solution 8.2.1 Example 1: system with distributed mass and elasticity 8.2.2 Example 2: system with distributed elasticity and lumped mass 8.2.3 Example 3: general systems Part II Introduction to Earthquake Engineering Contents xv 9 Seismology and Earthquakes 9.1 Basic concepts of seismology 9.1.1 Earthquake Genesis 9.1.2 Seismological Parameters 9.1.3 Waves Propagation 9.1.4 Attenuation Relationship 9.2 Ground motion parameters 9.2.1 Peak Parameters 9.2.2 Frequency and energetic content 9.2.3 Duration 9.2.4 Other parameters 10 Major seismic events that occurred in Italy and in the world 10.1 Introduction 10.2 Earthquakes occurred in Italy in the past 150 years 10.3 Earthquakes occurred in the World from 1960 to the present day 11 Seismic Hazard Analysis 11.1 Deterministic Seismic Hazard Analysis (DSHA) 11.2 Probabilistic Seismic Hazard Analysis (PSHA) 12 Earthquake prediction 12.1 General aspects 12.2 Prediction methods 12.2.1 Animal behavior 12.2.2 Changes in VP/VS 12.2.3 Radon emission 12.2.4 Electromagnetic variations 12.2.5 Precursory seismicity patterns 12.3 Earthquake prediction and time-dependent seismic hazard scenarios 12.3.1 Algorithms for intermediate-term middle range earthquake prediction 12.3.2 Neo-deterministic time-dependent seismic hazard scenarios for the Italian territory 12.4 Notable predictions 12.4.1 Haicheng (China, 1975) 12.4.2 Parkfield (USA, 1985-1993) 12.4.3 Loma Prieta (USA, 1989) 12.4.4 L'Aquila (Italy, 2009) 13 Seismic Input . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 285 13.1 Brief History of Italian Seismic Standards . . . . . . . . . . . . . . . . . . . . . . 285 13.2 Elastic Response Spectra . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 287 13.3 Uniform Hazard Spectrum (UHS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 289 13.4 Design Response Spectrum (DS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 291 13.4.1 Design Response spectrum according to NTC08 and EC8 . . 292 xvi Contents 13.4.2 Conditional Mean Spectrum (CMS) . . . . . . . . . . . . . . . . . . . . . 300 13.5 Use of Acceleration time histories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 302 13.5.1 Ground Motion Selection and Modification . . . . . . . . . . . . . . 304 13.5.2 Available Databases for