Dynamic Analysis

In radio transmission, spectrum analysis is about looking at the resonance of the circuit [read 'structure'] in response to input frequencies [read 'wind/tide/earthquake'].

Time history analysis sounds like looking at the deterioration of the structure over time.

Does that help?

What do local procedures and Codes of Practice say on the subject?

The amplitude of the dynamic variable is considered in the "frequency" domain rather than a "time" domain because it is more convenient and useful.

My guess is that the "dynamic analysis" that OP is interested in is either a sound wave or a shock wave (earthquake).

Typically, this would be done to get a nice graph of a log function.

Spectrum analysis takes the input wave forms (as from a Fourier analysis breakdown of earthquake or wind loads over a slice of time) and excites the structure which has a series of natural frequencies. An output amplitude of movement and hence internal forces can be derived. It is the application of input wave to natural frequency.

Time history takes a measurement of a real quake or wind tunnel test over a slice of time and then applies these loads in discrete intervals to the structural model to excite a response.

There is some debate about which is the most effective at predicting the reponse of a structure. The time history method requires significant amounts of computer power and has only been done on a few models for wind loading (although with success as the City of Manchester Stadium shows).

For quake loads, both methods can be used. It probably depends on your available data.

oh,

We can say like this, they look like a man and his shadow. you can judge a man's move by his shadow shift. more or less, they are like twists. sometimes, you cannt split them apart.

dynamic analysis is very often seeing in our job. almost in every field cn see it.

machine, electric, themal, etc .

This may owed to Fourier who found the relationship and described in math. refer to #3

earthquake, terrible thing. lets forget it as soon as possible.

give a n other example, vibrication analysis, say impulse response, yo u can entry frequency field to see what happened. use power spectrum you can detect flaw of a car etc.

use it you can analysis a circuit is stable or unstable. too many contents include analog and digital need you learn for a life. in one words, if you can get nothing in time field you hve to find some thing in frequecy field.

go on and study hard.

Thank you for your response sirs.

Presently am studying Staad Pro, and am start pulling my hair bout this dynamics analysis. In response spectrum analysis UBC97 section 1631.5 has recommendation of spectral acceleration versus period. Time history analysis of section 1631.1(UBC 97) shall be performed with pairs of appropriate horizontal ground motion. What are the appropriate ground motion?