Article Relationship between Peak Ground Acceleration, Peak Ground V...

Thanks for your reference, I will look into that.

Regards

Danilo

PGV and PGA occur at different times and the ratio PGV/PGA has dimensions of time - beats me there should be any significance.

Thanks Kevin Mccue ,

my question was more focused on the influence of such ratio on the severity of the ground motion as well as on the damage potential of structures.

Regards,

Danilo

Danilo

My answer is still the same - no obvious influence. Suppose both pga and pga are high you would expect high damage but the ratio is of order 1s. On the other hand if both pga and pga are low we expect no damage however the ratio is the same , of order 1s.

You might get some sense out of a number like pgv squared which should be very sensitive to damage potential.

Cheers

Kevin

Dear Claudio Pedrazzi

there are very few studies on that, and actually, they are quite old.

I will reflect on your comment, trying to find authoritative references confirming that. Thanks for your comment.

Dear Kevin Mccue ,

I see your point, but if we consider strong motions having the same PGA (and so, the same hazard), but different PGA/PGV ratio, such ratio should reasonably affect the severity of the accelerogram on the structure. I suppose higher velocities (at given acceleration) are considered more demanding on structures.

Would not you agree?

Dear Danilo,

In the case that You haven't read it yet, there is an article that shows that the ratio of PGA/PGV indicates the relative frequency content of the ground motion:

Article Engineering implication of ground motion A/V ratio

Bommer et al. (2010) futher suggested that the PGV to PGA ratios are directly and linearly related to TC in Eurocode 8 (the higher limit period of the constant spectral acceleration branch), since the short-period amplitudes are related to PGA and the intermediate-period amplitudes to PGV, and since the period TC can be considered as the transition between these two sections of the spectrum:

Article Current empirical ground-motion prediction equations for Eur...

Trelation between damages and PGV/PGA ratios.I hope You would find this helpful in Your study of

All the best,

Borko Bulajic

Something happened with my keyboard. The last part of my answer was supposed to be:

The direct relation between damages and PGV/PGA ratios is however still not clear.

I hope You would find this helpful in Your study.

All the best,

Borko Bulajic

Dear Borko Bulajić ,

thanks for your references.

I had only found the first one, which is quite old;

I will read with great interest the second one, that is more recent.

Thanks again for your support.

Best regards,

Danilo

Dear All,

PGV/PGA is one of 23 parameters of a seismic record. I think it represents the frequency content, somehow similar to Predominant Period (Tp) and Mean Period (Tm). It does not represent the intensity of an earthquake.

As illustrated by Claudio Pedrazzi using a sine function, PGV/PGA relates to T if the time t is the same. How about at different time t?

Best wishes,

Vui Van Cao

Dear Vui Cao,

When I said that PGV/PGA ratio seems to affect the severity of the ground motion, I meant the severity in terms of damage potential on structures. I did not mean that such ratio represents the input intensity (often represented by acceleration peaks or spectral accelerations).

As you and Claudio Pedrazzi

When there is not significant time corresponding between the two featues, I guess that the actual V(tPGA)/PGA (or PGV/A(tPGV)) ratio assumes the above-mentioned meaning, and the PGV/PGA ratio is much less significant on the spectral response of the ground motion as well as on the severity of the input on dynamic behaviour of structures and related damage potential.

Would you be agreed on that?

Good question.. Please share me the best answer might you trust...

Regards…

Bommer, et al., in "COMPATIBLE ACCELERATION AND DISPLACEMENT SPECTRA FOR SEISMIC DESIGN CODES", 12th World Conference on Earthquake Engineering have suggested hat 5PGV/PGA is the approximate period at which the acceleration spectrum begins to descend from the plateau - the high end period defining the constant acceleration spectrum plateau. In the same paper, it is suggested that 8PGD/PGV is the approximate period defining the low end of the constant spectral displacement plateau. As both measures have units of seconds, it seems that the best interpretation to date is that the parameters are an indicator of frequency content.

Consider a SHM for which displacement y = Acos(wt+B), Then velocity v = -wAsin (wt+B) and acceleration = -Aw2cos(wt+B). Thus the ratio PGV/PGA = 1/w i.e. the inverse of the circular frequency = 1/(2πf) = T/(2π ).

In actual fact the earthquakes are not SHM but has time varying frequency and amplitude. The motion can be decomposed into an approximate sum of simple harmonics of varying magnitude of a certain frequency. However, the higher harmonics are of much smaller amplitude. Consequently, the PGV/PGA = T1/(2π ) where T1 = fundamental period of the earth quake.

Dear Claudio Pedrazzi

thanks for your comment.

I would not expect as well a (direct) proportionality between the PGV/PGA ratio and the (general) damage, as well as I clearly see the importance of the structural frequency sensitivity (e.g., vibration periods) on such aspect. On the other side, I would like to know if there are (any) correlations between such parameter and the structural damage, and what is the possible quantitative influence of such ratio on damage of structures having various dynamic characteristics. I think this issue is being interestingly addressed by all these comments, as well I can sense the interest of the researchers on this topic. Thanks for this contributions.

Dear Timothy Huff and Amaechi J. Anyaegbunam (I tried to tag you with without success),

thanks for your technical contribution on the dynamic interpretation of the PGV/PGA ratio. The correlation between such ratio and the ground motion response spectrum was traced by other colleagues, but now, thanks to your comments, we also have specific details involving the dynamic motion equations.

I will look into the reference suggested and on the dynamic explanation.

Regards,

Danilo

Dear All,

May I ask you please a reference in which the all standard characteristics of a ground motion are defined and described, please?

Vui Cao mentioned that PGV/PGA is one of the 23 parameters of a seismic input, but I was not able to find where this is reported.

Many thanks in advance.

Danilo

The help files for both SeismoSignal and Seismospect programs each go into great detail about the calculation and definition of many ground motion parameters. The programs will also calculate the parameters, as well as elastic and inelastic spectra, for a given accelerogram. The software is free for educational use (www.seismosoft.com).

SeismoSignal and the following papers could be helpful.

Cao, V.V., and Ronagh, H., (2014), "Correlation between parameters of pulse-type motions and damage of low-rise RC frames". Earthquakes and Structures, 7(3), 365-384, doi: http://dx.doi.org/10.12989/eas.2014.7.3.365

Cao, V.V., and Ronagh, H.R., (2014), "Correlation between seismic parameters of far-fault motions and damage indices of low-rise reinforced concrete frames". Soil Dynamics and Earthquake Engineering, 66, 102-112. doi: http://dx.doi.org/10.1016/j.soildyn.2014.06.020

Best wishes,

Vui V Cao

Thanks a lot for the reference as well as for the program suggestion!

regards,

danilo

Dear Mohamed Beneldjouzi,

thanks for your contribution.

Do you have reference addressing the PGV/PGA damage correlations to structures?

Kind regards,

Danilo

There is no meaning in the ratio. They occur at different times and at different frequencies. PGV may have some correlation with damage, a measure of the kinetic energy, but pga has no obvious correlation with damage. Even small earthquakes can generate a pga of 1g, if you are close to the focus and the accelerometer is on rock.

There is a relation between PGA/PGV ratio and frequency content of seismic record. The more the record is shifted towards higher frequencies the higher is the ratio of PGA/PGV. For typical natural earthquakes PGA/PGV could about 10 (e.g. ElCentro record), while for surface records of induced seismic events (e.g. rockbursts) it takes higher values. See e.g. my paper from SDEE: ZEMBATY Z., Rockburst induced ground motion - a comparative study, Soil Dynamics & Earthquake Engineering, vol.24, no.1, January 2004, pp. 11-23. For natural earthquake records in close vicinity of epicenters PGA/PGV is also higher because of frequency content shift.

Considering a sine function representing velocity history of the form v(t)= A*sinwt

Naturally acceleration a(t)= Aw*coswt. If one considers the positive value of

peak of a(t)/peak of v(t), then we get the frequency of excitation. This explain why PGA/PGV is a measure of frequency content.

The explanations presented above by Rana Roy explains what happens with single harmonics and is holds in a slightly more complicated manner for actual time history records as any time history record can be presented as a sum of harmonic. The peaks calculated in different time instants makes the quantitative formulae more complicated but generally presence of 'w' (omega) as multiplier in differentiation is a dominating effect.

Thank you Sir (Prof. Zembaty) for further explanation. Rana

Thanks a lot for the further comments; such ratio is resulting more significant than it is commonly considered. I found an interesting literature also relating the ratio to the damage potential of civil structures, in addition to the known seismological meaning.

The problem of dependence between parameters of seismic record close to a building (or at foundation) and its structural damages is difficult to be solved unambiguously. It is PGV which is best correlated with damage. Obviously strong motion duration could be the 2nd important parameter. In my opinion PGA/PGV can be a measure of structural damage to the extend in which peak velocity is represented in this ratio. From this point of view perhaps the inversion: PGV/PGA could be worth investigating as a measure of structural damage.

Analysis of ground motion data shows that there is no clear correlation between PGA/PGV and predominant frequency (Tp).

You may like to refer to the attached book chapter "Correlating Peak Ground A/V ratio with Ground Motion Frequency Content".

quote "...there is no clear correlation between PGA/PGV and predominant frequency...". This may not be clear for natural earthquakes. Yet with clear shit of the Fourier spectrum to higher frequencies as is with rockbursts PGA/PGV increases obviously. This may be an effect that for "type II" rockbursts there is vary small contribution of the spectrum from 0 to 5Hz. See: ZEMBATY Z., Rockburst induced ground motion - a comparative study, Soil Dynamics & Earthquake Engineering, vol.24, no.1, January 2004, pp. 11-23.

PGA is a good measure of high-frequency ground motions (5 to 10 Hz), whilst PGV is indicative of motions at intermediate frequencies (1 to 2 Hz). Thus, high-frequency structures tend to be sensitive to PGA and low-frequency structures tend to be more sensitive to PGV.

Hi!

For the case of underground structures, Hashash et al. 2001 is given values of PGV/PGA for different earthquake magnitudes for both soil and rocky strata. In fact, these values were proposed by Power et al. 1998. Please find attached the link for this:

Citation:

Hashash, Youssef MA, Jeffrey J. Hook, Birger Schmidt, I. John, and Chiang Yao. "Seismic design and analysis of underground structures." Tunnelling and underground space technology 16, no. 4 (2001): 247-293.

Link for paper:

Article Seismic design and analysis of underground structure

Regards,

Abdullah Ansari

The PGV to PGA ratio is known as a significant parameter for the damage assessment of structures under earthquake shakings. As a matter of factratio PGV/PGA = 1/w i.e. the inverse of the circular frequency = 1/(2πf) = T/(2π ). In actual fact the earthquakes are not SHM but has time varying frequency and amplitude. The motion can be decomposed into an approximate sum of simple harmonics of varying magnitude of a certain frequency.