“STRUCTURAL RESPONSE OF MASONRY

BUILDINGS IN THE HISTORIC CENTER OF

GENOA, ITALY”

S. Barani1,2, R. De Ferrari1,2, S. Cattari3, C. Eva2, S. Lagomarsino3 and A. Pieracci4

1Dipartimento di Scienze della Terra dell’Ambiente e della Vita, Università di Genova, Italy 2GEAmb S.r.l., spin-off dell’Università di Genova, Genova, Italy 3Dipartimento di Ingegneria Civile, Chimica e Ambientale, Università of Genova, Italy 4Autorità Portuale di Genova, Italy

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Genova

Simplified geological map and maximum p.c.p.v. values recorded on the top floor of each

building along the horizontal component

The Experiment

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Instruments

Solgeo Veloget 3D 1s

Solgeo Dimas 24

Solgeo Veloget 3D 1s

Solgeo Dimas 24

LE-3D/5s

LE MARSlite

LE-3D/5s

LE MARSlite

B1

B2 B3

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Instruments were placed

close to vertical load resisting

elements (e.g., walls) with the

longitudinal axis (X axis)

parallel to the longer side of

the building

Data & Data Processing

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1- Blasts (signals were recorded in time windows of 10 s)

2- Ambient noise

3- Earthquakes (only @ B3)

October 3, 2012 Piacenza earthquake

Ml = 4.5, ≈ 80 km from Genoa Blast recordings

Signals were employed to calculate:

a) HVSRs @ all sites

b) SSRs @ B3

Fourier spectra were smoothed

using the Konno and Ohmachi

(1998) function with a smoothing

coefficient of 20

Building B1

Ambient Noise Blasts

Fourier

Spectra

HVSR

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Basement of B1 «Free Field»

HVSR

Building B2

Ambient Noise Blasts

Fourier

Spectra

HVSR

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Building B3

Ambient Noise Blasts

Blasts - Y Blasts - X Blasts - Z

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Fourier Spectra

(Lagomarsino, BEE, 2014)

Experimental Vs Analytical Floor Spectra

Experimental spectra

were calculated from the

recordings of the October

3, 2012 Piacenza

earthquake (Ml = 4.5)

Analytical floor spectra

accounts for the

contribution of the first

mode only

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T1 = 0.33s

(= 3Hz) T2 = 0.13s

(= 7.7Hz)

H/V spectral ratios from noise recordings are consistent with those calculated using

blast signals, thus indicating that the eigenfrequency of vibration of a structure (as

derived from HVSRs) is insensitive to source signal (i.e., input excitation)

Although ambient noise H/V measurements represent an economical and flexible

alternative to SSRs, they could lead to misleading results in that it may not be possible

to distinguish the eigenfrequencies of the building from the resonance frequencies of

the foundation soil (unless they are known from free field measurements). Therefore,

the application of the SSR technique may be preferable in densely urbanized

environments where free field H/V measurements may be affected by the presence of

buildings

The amplitude of the peaks obtained from H/V spectral ratios differs from that

determined by using a reference station. As a consequence, H/V curves can not be

assumed as representative of the absolute amplification level

Conclusions

H/V spectral ratios and SSRs may be very useful to support the seismic assessment

of buildings, in order to calibrate both numerical models and the seismic demand to be

adopted in the evaluation of local mechanisms that involve the upper parts of the

structures

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Genova