جزییات کتاب
دینامیک سازه زیر شاخهای است از تحلیل سازهها و تئوری ارتعاشات که به آنالیز و مطالعه رفتار سازهها تحت اثر بارهای دینامیکی میپردازد.
بارهای وارده بر سازه در بعضی موارد ممکن است از نظر مقدار، جهت و موقعیت تغییراتی نسبت به زمان داشته باشند. این بارها را اصطلاحاً بارهای دینامیکی گویند. در چنین حالتی رفتار سازه «مقادیر تغییر شکلها، نیروهای داخلی و تنشها» وابسته به زمان خواهد بود؛ بنابراین رفتار سازه در این حالت بر عکس رفتار استاتیکی آن جواب منحصربهفردی نخواهد داشت، بلکه در هر لحظه از زمان، رفتار خاصی برای آن موجود خواهد بود که به آن رفتار دینامیکی میگویند.
در اثر اعمال بارهای دینامیکی، تغییر مکان حاصله همراه با سرعت و شتاب خواهد بود. جهت مقابله با شتاب وارده، نیرویی به نام نیروی لختی در اثر جرم و جهت مقابله با سرعت، نیروی میرایی در اثر اصطکاک بین ذرات، لقی اتصالات و غیره بوجود میآید؛ بنابراین نیروهای داخلی سازه نه تنها میباید با بارگذاری اعمال شده بر آن در تعادل باشند، بلکه نیروهای لختی ناشی از شتاب و میرایی ناشی از سرعت نیز در تعادل مؤثر میباشند. از جمله اثرات دینامیکی وارد بر سازهها و ساختمانها میتوان به موارد زیر اشاره کرد:
اثر زلزله
نیروی باد
نیروی ناشی از امواج بر سازههای دریایی
اثر انفجارها
بارهای متحرک ترافیکی
پی ماشین آلات
Designed for senior-level and graduate courses in Dynamics of Structures and Earthquake Engineering. Dynamics of Structures includes many topics encompassing the theory of structural dynamics and the application of this theory regarding earthquake analysis, response, and design of structures. No prior knowledge of structural dynamics is assumed and the manner of presentation is sufficiently detailed and integrated, to make the book suitable for self-study by students and professional engineers.FeaturesSection on application of the inelastic design spectrum to structural design – For allowable ductility, seismic evaluation of existing structures, and displacement-based structural design.Examples on dynamics of bridges and their earthquake response.Incorporation of three building codes and inclusion of the Eurocode.Theory of dynamic response of structures – Presented in a manner that emphasizes physical insight into the analytical procedures.Structural dynamics theory – Applied to conduct parametric studies that bring out several fundamental issues in the earthquake response and design of multistory buildings.Analytical procedures – Illustrated by over 100 worked out examples.Over 400 figures carefully designed and executed to be pedagogically effective. Photographs of structures and their responses recorded during earthquakes – Included to relate the presentation to the real world.Table of ContentsForeword xxiPreface xxiiiAcknowledgments xxxiPART I SINGLE-DEGREE-OF-FREEDOM SYSTEMS 11 Equations of Motion, Problem Statement, and Solution Methods 31.1 Simple Structures 31.2 Single-Degree-of-Freedom System 71.3 Force—Displacement Relation 81.4 Damping Force 121.5 Equation of Motion: External Force 141.6 Mass—Spring—Damper System 191.7 Equation of Motion: Earthquake Excitation 231.8 Problem Statement and Element Forces 261.9 Combining Static and Dynamic Responses 281.10 Methods of Solution of the Differential Equation 281.11 Study of SDF Systems: Organization 33Appendix 1: Stiffness Coefficients for a Flexural Element 332 Free Vibration 392.1 Undamped Free Vibration 392.2 Viscously Damped Free Vibration 482.3 Energy in Free Vibration 562.4 Coulomb-Damped Free Vibration 573 Response to Harmonic and Periodic Excitations 65Part A: Viscously Damped Systems: Basic Results 663.1 Harmonic Vibration of Undamped Systems 663.2 Harmonic Vibration with Viscous Damping 72Part B: Viscously Damped Systems: Applications 853.3 Response to Vibration Generator 853.4 Natural Frequency and Damping from Harmonic Tests 873.5 Force Transmission and Vibration Isolation 903.6 Response to Ground Motion and Vibration Isolation 913.7 Vibration-Measuring Instruments 953.8 Energy Dissipated in Viscous Damping 993.9 Equivalent Viscous Damping 103Part C: Systems with Nonviscous Damping 1053.10 Harmonic Vibration with Rate-Independent Damping 1053.11 Harmonic Vibration with Coulomb Friction 109Part D: Response to Periodic Excitation 1133.12 Fourier Series Representation 1143.13 Response to Periodic Force 114Appendix 3: Four-Way Logarithmic Graph Paper 1184 Response to Arbitrary, Step, and Pulse Excitations 125Part A: Response to Arbitrarily Time-Varying Forces 1254.1 Response to Unit Impulse 1264.2 Response to Arbitrary Force 127Part B: Response to Step and Ramp Forces 1294.3 Step Force 1294.4 Ramp or Linearly Increasing Force 1314.5 Step Force with Finite Rise Time 132Part C: Response to Pulse Excitations 1354.6 Solution Methods 1354.7 Rectangular Pulse Force 1374.8 Half-Cycle Sine Pulse Force 1434.9 Symmetrical Triangular Pulse Force 1484.10 Effects of Pulse Shape and Approximate Analysis forShort Pulses 1514.11 Effects of Viscous Damping 1544.12 Response to Ground Motion 1555 Numerical Evaluation of Dynamic Response 1655.1 Time-Stepping Methods 1655.2 Methods Based on Interpolation of Excitation 1675.3 Central Difference Method 1715.4 Newmark’s Method 1745.5 Stability and Computational Error 1805.6 Nonlinear Systems: Central Difference Method 1835.7 Nonlinear Systems: Newmark’s Method 1836 Earthquake Response of Linear Systems 1976.1 Earthquake Excitation 1976.2 Equation of Motion 2036.3 Response Quantities 2046.4 Response History 2056.5 Response Spectrum Concept 2076.6 Deformation, Pseudo-velocity, and Pseudo-acceleration Response Spectra 2086.7 Peak Structural Response from the Response Spectrum 2176.8 Response Spectrum Characteristics 2226.9 Elastic Design Spectrum 2306.10 Comparison of Design and Response Spectra 2396.11 Distinction between Design and Response Spectra 2416.12 Velocity and Acceleration Response Spectra 242Appendix 6: El Centro, 1940 Ground Motion 2467 Earthquake Response of Inelastic Systems 2577.1 Force—Deformation Relations 2587.2 Normalized Yield Strength, Yield Strength Reduction Factor, and Ductility Factor 2647.3 Equation of Motion and Controlling Parameters 2657.4 Effects of Yielding 2667.5 Response Spectrum for Yield Deformation and Yield Strength 2737.6 Yield Strength and Deformation from the Response Spectrum 2777.7 Yield Strength—Ductility Relation 2777.8 Relative Effects of Yielding and Damping 2797.9 Dissipated Energy 2807.10 Supplemental Energy Dissipation Devices 2837.11 Inelastic Design Spectrum 2887.12 Applications of the Design Spectrum 2957.13 Comparison of Design and Response Spectra 3018 Generalized Single-Degree-of-Freedom Systems 3058.1 Generalized SDF Systems 3058.2 Rigid-Body Assemblages 3078.3 Systems with Distributed Mass and Elasticity 3098.4 Lumped-Mass System: Shear Building 3218.5 Natural Vibration Frequency by Rayleigh’sMethod 3288.6 Selection of Shape Function 332Appendix 8: Inertia Forces for Rigid Bodies 336PART II MULTI-DEGREE-OF-FREEDOM SYSTEMS 3439 Equations of Motion, Problem Statement, and Solution Methods 3459.1 Simple System: Two-Story Shear Building 3459.2 General Approach for Linear Systems 3509.3 Static Condensation 3679.4 Planar or Symmetric-Plan Systems: Ground Motion 3709.5 One-Story Unsymmetric-Plan Buildings 3759.6 Multistory Unsymmetric-Plan Buildings 3819.7 Multiple Support Excitation 3859.8 Inelastic Systems 3909.9 Problem Statement 3909.10 Element Forces 3919.11 Methods for Solving the Equations of Motion: Overview 39110 Free Vibration 401Part A: Natural Vibration Frequencies and Modes 40210.1 Systems without Damping 40210.2 Natural Vibration Frequencies and Modes 40410.3 Modal and Spectral Matrices 40610.4 Orthogonality of Modes 40710.5 Interpretation of Modal Orthogonality 40810.6 Normalization of Modes 40810.7 Modal Expansion of Displacements 418Part B: Free Vibration Response 41910.8 Solution of Free Vibration Equations: Undamped Systems 41910.9 Systems with Damping 42210.10 Solution of Free Vibration Equations: Classically Damped Systems 423Part C: Computation of Vibration Properties 42610.11 Solution Methods for the Eigenvalue Problem 42610.12 Rayleigh’s Quotient 42810.13 Inverse Vector Iteration Method 42810.14 Vector Iteration with Shifts: Preferred Procedure 43310.15 Transformation of kφ = ω2mφ to the Standard Form 43811 Damping in Structures 445Part A: Experimental Data and Recommended Modal Damping Ratios 44511.1 Vibration Properties of Millikan Library Building 44511.2 Estimating Modal Damping Ratios 450Part B: Construction of Damping Matrix 45211.3 Damping Matrix 45211.4 Classical Damping Matrix 45311.5 Nonclassical Damping Matrix 46212 Dynamic Analysis and Response of Linear Systems 465Part A: Two-Degree-of-Freedom Systems 46512.1 Analysis of Two-DOF Systems without Damping 46512.2 Vibration Absorber or Tuned Mass Damper 468Part B: Modal Analysis 47012.3 Modal Equations for Undamped Systems 47012.4 Modal Equations for Damped Systems 47312.5 Displacement Response 47412.6 Element Forces 47512.7 Modal Analysis: Summary 475Part C: Modal Response Contributions 48012.8 Modal Expansion of Excitation Vector p(t) = sp(t) 48012.9 Modal Analysis for p(t) = sp(t) 48412.10 Modal Contribution Factors 48512.11 Modal Responses and Required Number of Modes 487Part D: Special Analysis Procedures 49412.12 Static Correction Method 49412.13 Mode Acceleration Superposition Method 49712.14 Mode Acceleration Superposition Method: Arbitrary Excitation 49813 Earthquake Analysis of Linear Systems 511Part A: Response History Analysis 51213.1 Modal Analysis 51213.2 Multistory Buildings with Symmetric Plan 51813.3 Multistory Buildings with Unsymmetric Plan 53713.4 Torsional Response of Symmetric-Plan Buildings 54813.5 Response Analysis for Multiple Support Excitation 55213.6 Structural Idealization and Earthquake Response 558Part B: Response Spectrum Analysis 55913.7 Peak Response from Earthquake Response Spectrum 55913.8 Multistory Buildings with Symmetric Plan 56413.9 Multistory Buildings with Unsymmetric Plan 57613.10 A Response-Spectrum-Based Envelope for Simultaneous Responses 58413.11 Response to Multi-Component Ground Motion 59214 Analysis of Nonclassically Damped Linear Systems 613Part A: Classically Damped Systems: Reformulation 61414.1 Natural Vibration Frequencies and Modes 61414.2 Free Vibration 61514.3 Unit Impulse Response 61614.4 Earthquake Response 617Part B: Nonclassically Damped Systems 61814.5 Natural Vibration Frequencies and Modes 61814.6 Orthogonality of Modes 61914.7 Free Vibration 62314.8 Unit Impulse Response 62814.9 Earthquake Response 63214.10 Systems with Real-Valued Eigenvalues 63414.11 Response Spectrum Analysis 64214.12 Summary 643Appendix 14: Derivations 64415 Reduction of Degrees of Freedom 65315.1 Kinematic Constraints 65415.2 Mass Lumping in Selected DOFs 65515.3 Rayleigh—Ritz Method 65515.4 Selection of Ritz Vectors 65915.5 Dynamic Analysis Using Ritz Vectors 66416 Numerical Evaluation of Dynamic Response 66916.1 Time-Stepping Methods 66916.2 Linear Systems with Nonclassical Damping 67116.3 Nonlinear Systems 67717 Systems with Distributed Mass and Elasticity 69317.1 Equation of Undamped Motion: Applied Forces 69417.2 Equation of Undamped Motion: Support Excitation 69517.3 Natural Vibration Frequencies and Modes 69617.4 Modal Orthogonality 70317.5 Modal Analysis of Forced Dynamic Response 70517.6 Earthquake Response History Analysis 71217.7 Earthquake Response Spectrum Analysis 71717.8 Difficulty in Analyzing Practical Systems 72018 Introduction to the Finite Element Method 725Part A: Rayleigh—Ritz Method 72518.1 Formulation Using Conservation of Energy 72518.2 Formulation Using Virtual Work 72918.3 Disadvantages of Rayleigh—Ritz Method 731Part B: Finite Element Method 73118.4 Finite Element Approximation 73118.5 Analysis Procedure 73318.6 Element Degrees of Freedom and Interpolation Functions 73518.7 Element Stiffness Matrix 73618.8 Element Mass Matrix 73718.9 Element (Applied) Force Vector 73918.10 Comparison of Finite Element and Exact Solutions 74318.11 Dynamic Analysis of Structural Continua 744PART III EARTHQUAKE RESPONSE, DESIGN, AND EVALUATION OF MULTISTORY BUILDINGS 75119 Earthquake Response of Linearly Elastic Buildings 75319.1 Systems Analyzed, Design Spectrum, and Response Quantities 75319.2 Influence of T1 and Á on Response 75819.3 Modal Contribution Factors 75919.4 Influence of T1 on Higher-Mode Response 76119.5 Influence of Á on Higher-Mode Response 76419.6 Heightwise Variation of Higher-Mode Response 76519.7 How Many Modes to Include 76720 Earthquake Analysis and Response of Inelastic Buildings 771Part A: Nonlinear Response History Analysis 77220.1 Equations of Motion: Formulation and Solution 77220.2 Computing Seismic Demands: Factors To Be Considered 77320.3 Story Drift Demands 77720.4 Strength Demands for SDF and MDF Systems 783Part B: Approximate Analysis Procedures 78420.5 Motivation and Basic Concept 78420.6 Uncoupled Modal Response History Analysis 78620.7 Modal Pushover Analysis 79320.8 Evaluation of Modal Pushover Analysis 79820.9 Simplified Modal Pushover Analysisfor Practical Application 80321 Earthquake Dynamics of Base-Isolated Buildings 80521.1 Isolation Systems 80521.2 Base-Isolated One-Story Buildings 80821.3 Effectiveness of Base Isolation 81421.4 Base-Isolated Multistory Buildings 81821.5 Applications of Base Isolation 82422 Structural Dynamics in Building Codes 831Part A: Building Codes and Structural Dynamics 83222.1 International Building Code (United States), 2009 83222.2 National Building Code of Canada, 2010 83522.3 Mexico Federal District Code, 2004 83722.4 Eurocode 8, 2004 84022.5 Structural Dynamics in Building Codes 842Part B: Evaluation of Building Codes 84822.6 Base Shear 84822.7 Story Shears and Equivalent Static Forces 85222.8 Overturning Moments 85422.9 Concluding Remarks 85723 Structural Dynamics in Building Evaluation Guidelines 85923.1 Nonlinear Dynamic Procedure: Current Practice 86023.2 SDF-System Estimate of Roof Displacement 86123.3 Estimating Deformation of Inelastic SDF Systems 86423.4 Nonlinear Static Procedures 87023.5 Concluding Remarks 876A Frequency-Domain Method of Response Analysis 879B Notation 901C Answers to Selected Problems 913Index 929