Guralp-systems ART Manual de usuario descargar pdf (Pagina 31)

User guide

calculated. The response spectra calculation must be

run again if the limits given in the ‘Options’ window

are changed after the response spectra calculation

was made);

20. Arias intensity (AI) in velocity units based on the

selected acceleration unit calculated from

where g is acceleration due to gravity in ms

-2

(i.e.

g=9.80665ms

-2

) and a(t) is ground acceleration (Arias,

1970);

21. normalized energy density (ED) in units based on the

selected velocity unit calculated from

where v(t) is ground velocity [see Sarma (1971)] [note

that, to get the true energy density, the normalized

energy density should be multiplied by Vρ/4 where V

is wave velocity and ρ is mass density of the

recording site (Sarma, 1971)];

22. cumulative absolute velocity (CAV) in selected

velocity units calculated from

where

a(t)

is the ground acceleration,

is the number

of 1-second time windows in the time series,

PGA

the PGA (in g) during time window i,

is the start time

of time window i,

min

is an acceleration threshold

(user-defined but commonly 0.025g) to exclude low

amplitude motions contributing to the sum and

H(x)

the Heaviside step function (unity for x>0 and 0

otherwise) (EPRI, 2006);

23. number of absolute effective cycles (peak counting

including non-zero crossings) in acceleration time-

history (Hancock & Bommer, 2005);

24. number of equivalent effective cycles using user-

defined damage exponent (peak counting including

non-zero crossings) in acceleration time-history

(Hancock & Bommer, 2005);

May 2009 31

AI =



∫

at

ED=

∫

v t

CAV =

∑

i=1

H  PGA

−a

min



∫

t=t

i1

∣a t ∣ dt

1 2 ... 26 27 28 29 30 31 32 33 34 35 36 ... 62 63

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