Time conversion factor
A conversion factor which multiplies the time contained in the accelerogram file. It is necessary to convert the time into seconds.
Acceleration conversion factor
A conversion factor which multiplies the acceleration contained in the accelerogram file. It is necessary to convert the acceleration into m/s2.
Separator used in the file
The separator used in the accelerogram file to divide the acceleration column from the time column.
Open
Import the accelerogram file.
Parameters
Arias intensity [Ia]
A parameter representing the index of intensity and frequency of the seismic waves. It is defined, less one constant, as the integral of the square of the accelerogram (extended to the whole duration of the earthquake).
Intensity of the intersections of the accelerogram with the time axis [ν0].
It is calculated as the ratio of the number of times the accelerogram intersects the time axis to the duration of the seismic event.
Duration of the seismic motion [TD]
The duration of the seismic motion defined by Trifunac (Trifunac & Brady 1975). It is calculated as the time interval elapsing between the attainment of 5% of Ia and 95% of Ia (Ia stands for Arias intensity).
Loaded accelerogram
On the loaded accelerogram, a scale factor which only affects its visualization is activated.
Calculation of the accelerogram integration parameters
Accelerogram parameters
The study of the issue relevant to the evaluation of the increase in the pore pressure in soils, in case of a seismic action, requires the calculation of some parameters aimed at identifying the frequency and intensity properties of the accelerogram. The parameters to be determined are the following:
•Arias intensity (Ia in m/s);
•Intensity of the intersections of the accelerogramm with the time axis (ν0 in 1/s);
•Actual duration of the motion defined by Trifunac (Trifunac and Brady, 1975, TD in s);
1. Arias intensity
Arias intensity is a parameter relevant to the accelerogram which provides information on the intensity and frequency of it. This parameter is defined according to the following ratio:
where
•TMAX represents the whole duration of the accelerogram;
•a(t) represents the accelerogram
As a rule, the values of this parameter vary between 0.05 and 2.5/3.
2. Intensity of the intersections with the time axis
This parameter is defined though the following formula:
where
•Ni is the number of times – throughout the duration of the accelerogram – the acceleration intersects the time axis;
•TMAX is the duration of the accelerogram.
3. Actual duration according to Trifunac
This parameter is used to identify the time interval elapsing between the following extreme cases:
where
According to the previously provided definitions, the time defined by Trifunac is equal to:
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