Dynamic calculations serve to describe the behaviour of a structure on time-variable loads.
Modal Analysis (Natural Frequency Measurement)
The natural frequency or eigenfrequency of a vibrating system is that at which it will vibrate after a nonrecurring excitation.
If you ignore the damping, eigenfrequency and resonance frequency are the same.
If a system is subjected to external excitation at a frequency coinciding with its natural frequency, the system will vibrate at a particularly high amplitude, which is known as resonance or, in case of damaging effects, as resonance catastrophe. Natural frequency measurement is determined computationally as eigenvalue problem.
Harmonic Response, Frequency Response Analysis
The response of a system after excitation by a harmonic load can be determined as function of the frequency via a so-called Harmonic Response Analysis, corresponding computationally to a test on the vibrating table with a sine sweep.
Impact Analysis, Shock
The response of a structure to an impact or shock can be determined via impact analysis. Here, load is specified as a function of time (e.g. half sinus).
Analysis of Randomness, Random Vibration, Spectral Analysis, Random Noise
The response of a structure to any time-variable load can be specified via a spectral analysis. However, time information gets lost here. Energy density at a frequency band is the given input and response of the structure is being determined by a conservative superimposition of the single vibration modes.