Single degree of freedom System: Structural Dynamics (Ch 2) Notes
Single degree of freedom System Notes
STRUCTURAL DYNAMICS (ENCE 365) – ELECTIVE I
Chapter 2: Single degree of freedom System
20 Hours | 30 Marks

Single degree of freedom System Notes

About this Chapter

Welcome to Chapter 2: Single-degree-of-freedom (SDOF) System of Structural Dynamics (ENCE 365). Carrying a major weightage of 30 Marks and 20 teaching hours, this chapter forms the analytical core of structural dynamic response evaluation.

This chapter provides a rigorous mathematical and physical breakdown of single-degree-of-freedom structural models. You will study free vibration responses (under-damped, critically damped, over-damped), logarithmic decrement, forced vibration response to harmonic, periodic, impulsive, and general dynamic loads via the Duhamel Integral. Additionally, the notes cover critical engineering applications like vibration isolation, transmissibility, measuring instruments, and computer simulations.

Syllabus (30 Marks)

2. Single degree of freedom System (20 hours)

2.1 Equations of motion: Modeling of Single degree of freedom System, response parameters, effect of gravity, effect of support excitation, combination of stiffness (Parallel and series)

2.2 Free vibration response: Undamped system; Damped system (Under critically, critically, and over critically)

2.3 Logarithmic decrement of response

2.4 Forced vibration response to harmonic loading: Undamped system; Damped systems (Transient response, steady-state response, general response, and resonance response)

2.5 Energy dissipated by damping (Viscous damping)

2.6 Forced vibration response to periodic loading: Undamped system (Transformation of loading and response using Fourier series)

2.7 Forced vibration response to impulsive load (Half-sine wave pulse, rectangular pulse, ramp pulse, triangular pulse)

2.8 Forced vibration response to general dynamic loading: Unit-impulse and Dirac-delta function; Unit-impulse response function; Duhamel integral and Convolution integral; Numerical evaluation of Duhamel integral

2.9 Vibration measuring instruments (Displacement meter and accelerometer)

2.10 Vibration isolation (Vertical oscillating force, harmonic motion of the base, force transmissibility, unbalanced mass amplitude of rotating unbalanced system)

2.11 Computer simulation of dynamic responses of Single degree of freedom System: Free; Forced; Undamped damped (Under critical, critical, and over critical); Resonance effect

Comprehensive Understanding of SDOF Systems

A deep understanding of Single degree of freedom Systems is indispensable for structural engineers modeling earthquake, blast, and machinery vibrations on elevated tanks, single-story frames, and isolated structures.

Authored by Associate Prof. Dr. Bharat Mandal (Pulchowk Campus), these notes comprehensively cover key examination concepts:

  • Modeling & Free Vibration: Formulating equations of motion for equivalent SDOF systems, combining series and parallel stiffnesses, calculating natural frequencies, damping ratios, and logarithmic decrement.
  • Harmonic & Periodic Forced Response: Evaluating transient and steady-state responses, dynamic magnification factors (DMF), resonance conditions, Fourier series transformations, and viscous energy dissipation.
  • Impulsive & General Loading: Step-by-step mathematical solutions for half-sine, rectangular, and triangular pulses, utilizing Dirac-delta functions, and numerical evaluation of the Duhamel Integral.
  • Isolation & Instrumentation: Designing base isolation systems, computing force and displacement transmissibility, operating principles of accelerometers, and simulating dynamic responses computationally.

Single degree of freedom System Notes

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