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Course Sheet Academic Year of enrolment:
Professor and Collaborators:
Hours of classroom activity:
Prerequisites:
Basic notions of Mathematical Analysis and Mechanics
Objectives
Contents Main contents of the course is the study of the basic notions of the dynamics of discrete linear sysems. The balance equations are fromulated and solved both analythically and numerically.
The concepts are introduced and used to solve mdof systems. Identification problems and seismic isolation are mentioned.
Extended Syllabus Introduction to Structural Dynamics
- Continuous systems vs. discrete systems
- Lumped parameter systems (notions of mass, stiffness and damping)
- Mathematical models of single degree of freedom systems
- Derivation of the equations of motion by the Newton’s law and D’Alembert principle
- Derivation of the equations of motion by the of the Principle of virtual displacements
Single Degree of Freedom (Sdof) Systems
Free vibrations
- Undamped vibrations
- Viscous damped vibrations
- Stability of motion
- Notions of frequency, period, amplitude and phase of the motion
Harmonic excitation
- Response of undamped Sdof systems to harmonic excitations
- Response of viscous damped Sdof systems to harmonic excitations
- Steady state response, resonance and beat phenomenon
- Equivalent viscous damping
Periodic excitation and harmonic analysis
- Periodic functions and Fourier series
- Fundamental frequency and Fourier coefficients
- Spectrum of a periodic function
- Evaluation of the steady state response of dynamic systems
General excitations
- Impulse, momentum and impulse response function
- Convolution integral method (Duhamel integral)
- Response of a viscous damped system to rectangular pulses and ramp loadings
Elements of numerical integration of the equations of motion
- Central difference method
- Newmark’s method
- Stability and accuracy of the numerical solution
Vibrations isolation: Force Transmissibility and Base motion
Elements of experimental dynamics
- Dynamic excitation devices
- Vibration measuring instruments: accelerometer
- Identification of natural frequency and damping factor
Multiple Degrees of Freedom (Mdof) Systems
2-dof systems
- Mathematical models of 2dof systems
- Matrix form of the equations of motion
- Free and forced (harmonic) vibrations
- Natural frequencies and mode shapes
- Principal coordinates and Modal analysis
- Vibration absorber
M-dof systems
- Generalization of 2-dof systems solutions
- Orthogonality of mode shapes and method of modes superpostion
- Participation coefficient, modal mass and modal stiffness
- Forced vibrations and base motion
- Rayleigh damping
Elements of vibration of continuous systems
- Derivation of the equations of motion by the Newton’s laws
- Axial, shear and torsional vibrations of beams
- Transverse vibrations of beams
Recommended Bibliography E. Viola “Fondamenti di Dinamica e Vibrazione delle Strutture (Vol. 1)”, Pitagora Editrice, 2001.
R.R. Craig jr, A.J. Kurdila “Fundamentals of Structural Dynamics (2nd ed.)”, Wiley, 2006.
A.K. Chopra “Dynamics of Structures (2nd ed.)”, Prentice Hall, 2000.
Teaching Methods The course is composed by theoretical lessons and practical activity in classroom supervised by the theacer. The practical activities consist of either the writing of algorithms for computer based solutions and the construction of simple mechanichal models to help the comprehension of vibrations.
Evaluation methods Verification of learning:
The learning is continuously monitored during the practical activities in classroom. A final test on the main subjects of the course completes the students evaluation
Contacts/More Information THe course frequency is strongly avdiced.