Elastic period of vibration calculated experimentally in buildings hosting permanent GPS stations

Abstract

During the earthquake in Emilia (Italy) of 2012, ca. 30 permanent GPS stations were in operation within a radius of about 100 km from the epicenter, each equipped with an antenna rigidly fixed to the host building and sampling the GPS signal at a high rate (> 1 Hz). From the recording of the GPS measurements, the instantaneous displacements s(t) in the North-South and East-West directions of the phase centers of the single GPS antennas at each permanent station during the most important seismic sequences were calculated in kinematic mode. Subsequently, for each of the two displacements considered as two distinct external forces, the elastic response spectra of the building were determined and from them the two periods of vibration T along two orthogonal directions coinciding with the walls of the building were extracted. The experimentally obtained periods of vibration were compared with those inferable from the technical literature. In this way, a sufficiently large sample was obtained per building type, geometry (square, rectangular, regular or irregular planimetry), height (from a minimum of 4 to a maximum of 20 m) and materials (masonry, reinforced concrete, etc.). From the computational point of view, the study confirmed that GPS is an emerging tool for monitoring dynamic displacements and the experimentally estimated value of T is always lower than the one estimated with the formulae reported in the literature. The limitations of the study lie in the impossibility to choose a priori the geometry and/or structural type of the building hosting the GPS station.

Relation between dynamic amplification, structural height and damage in buildings affected by the recent Italian earthquakes

“…The limits of the present study are: the difficulty in distinguishing the vulnerability due to construction materials and characteristics from that associated with resonance, especially in the L'Aquila and Central Italy areas characterized by low-quality materials; a non-rigorous dependence of T on H and the value of f, as demonstrated in recent works by the present author (Gatti 2018b(Gatti , 2018c.…”

Soil foundation and structure interaction effects on the estimating of fundamental period of instrumented buildings

“…Traditionally, the simplified formula adopted in the technical literature [37] relates the period of vibration to the height H of the building in the following form:…”

Experimental Calculation of the Damping Ratio In Buildings Hosting Permanent GPS Stations During the Recent Italian Earthquakes

“…Figure 4 reports an example of pseudo-acceleration spectra calculated from the horizontal GPS displacements recorded at the Concordia station (CONC) and from the accelerometric recordings at the RAN station of Moglia (MOG0), the latter only a few kilometers from the former, during the earthquake of 29 May 2012 07:00:03 UTC Mw 5.8. In this case, the Concordia GPS station has an elastic period of oscillation T o of 0.26 seconds [42]. The parabola constructed from the relation of the spectral ordinates obtained from the previous spectra as the damping ratio varies, for T o = 0.26, is reported in Figure 5.…”

“…It should be underlined that the calculation was verified also for T o values near to that of the structure, with the same results (Figure 5, parabolas constructed for T o = 0.25 and 0.27). The elastic period of vibration T o of each GPS station was calculated by means of a procedure described by Gatti [42].…”