Wave dispersion in high‐rise buildings due to soil–structure interaction

Abstract

SUMMARYNonparametric techniques for estimation of wave dispersion in buildings by seismic interferometry are applied to a simple model of a soil-structure interaction (SSI) system with coupled horizontal and rocking response. The system consists of a viscously damped shear beam, representing a building, on a rigid foundation embedded in a half-space. The analysis shows that (i) wave propagation through the system is dispersive. The dispersion is characterized by lower phase velocity (softening) in the band containing the fundamental system mode of vibration, and little change in the higher frequency bands, relative to the building shear wave velocity. This mirrors its well-known effect on the frequencies of vibration, i.e. reduction for the fundamental mode and no significant change for the higher modes of vibration, in agreement with the duality of the wave and vibrational nature of structural response. Nevertheless, the phase velocity identified from broader band impulse response functions is very close to the superstructure shear wave velocity, as found by an earlier study of the same model. The analysis reveals that (ii) the reason for this apparent paradox is that the latter estimates are biased towards the higher values, representative of the higher frequencies in the band, where the response is less affected by SSI. It is also discussed that (iii) bending flexibility and soil flexibility produce similar effects on the phase velocities and frequencies of vibration of a building.

Time‐wave velocity analysis for early earthquake damage detection in buildings: application to a damaged full‐scale RC building

“…The algorithm is intended for use in SHM systems for rapid assessment of the structural health and integrity following an earthquake. This confirmed that the method has the following characteristics: (i) robust when applied to full-scale structures and large amplitude response; (ii) sensitive to damage; and (iii) (another important property) not sensitive to the effects of soil-structure interaction even when foundation rocking is present [24][25][26]. An important feature of this method is that it is not sensitive to the effects of soilstructure interaction.…”

“…This confirmed that the method has the following characteristics: (i) robust when applied to full-scale structures and large amplitude response; (ii) sensitive to damage; and (iii) (another important property) not sensitive to the effects of soil-structure interaction even when foundation rocking is present [24][25][26]. This confirmed that the method has the following characteristics: (i) robust when applied to full-scale structures and large amplitude response; (ii) sensitive to damage; and (iii) (another important property) not sensitive to the effects of soil-structure interaction even when foundation rocking is present [24][25][26].…”

“…The identified average vertical wave velocity was initially~140 m/s for the NS and~110 m/s for the EW response and reduced bỹ 26% and 32%, respectively. In contrast, the wave method is not sensitive to this effect, which eliminates one of the major factors causing ambiguity in the interpretation of observed changes in the fundamental frequency [24][25][26]. The difference is interpreted to be due to softening of the soil-foundation system, to which the identified frequency of vibration is sensitive.…”

Detection thresholds in structural health monitoring

“…Those estimates appear to be robust and are realistic for all buildings for which such 1-D modeling is possible, and where earthquake damage has been documented and can be used to verify the modeling assumptions. However, more-detailed building models can and do provide more accurate estimates of changes in f 1 [90,94,75,76,[77][78][79]28,29]. Buildings with large plan dimensions relative to their height will require two-and occasionally threedimensional models, preferably with anisotropic properties.…”

Finite element model calibration of multi-story buildings through interferometric imaging and spectral ratio method

“…Furthermore, it is usually assumed that the building is perfectly fixed at foundation level. The wave velocity of a shear-beam building from broader band records D r a f t (roof-deconvolved) are less affected by the Soil Structure Interaction (SSI) because it is biased towards the values representative of higher frequencies, which are less effected by SSI; however, the wave propagation of the building on a flexible soil is still dispersive when foundation rocking is present (Rahmani et. al.…”