Eylem Seç
Elastodynamic Model for Wind Induced Ground Motion
Başlık:
Elastodynamic Model for Wind Induced Ground Motion
Yazar:
Mohammadi, Mohammad, author.
ISBN:
9780438068179
Yazar Ek Girişi:
Fiziksel Tanımlama:
1 electronic resource (81 pages)
Genel Not:
Source: Masters Abstracts International, Volume: 57-06M(E).
Advisors: Craig J. Hickey Committee members: Farhad Farzbod; Tyrus McCarty; Richard Raspet.
Özet:
Wind induced ground vibrations are a source of noise in seismic surveys. In a previous study, a wind-ground coupling theory was developed to predict the power spectral density (PSD) of ground motions caused by wind perturbations on the ground surface. The ground was assumed to respond as an elastic isotropic homogeneous medium deforming quasi-statically due to wind. Model predictions and field measurements were in agreement for the normal component of the displacement but under predicted the radial component. There are two possible explanations for the underestimation: the wind shear stresses are larger than the predictions or the quasi-static homogeneous ground model is unrealistic leading to underestimation. In this work, generalized ground models incorporating non-uniform grounds and dynamic deformations are evaluated in order to improve the prediction for the radial displacements and also evaluate the possible effect of ground structure on the wind-ground measurements. The static response of the ground is replaced by the analytic response of an elastic homogeneous half-space under the influence of a harmonic vertical surface load in the wind-ground equation. The normal component of dynamic predictions is in a good agreement with previous field measurements and predictions, whereas, the radial displacements of the dynamic model show an improvement compared to the static model. However, there is still a significant discrepancy between the predicted and measured displacements. The response function for three different types of non-uniform grounds: an inhomogeneous ground with increasing rigidity with depth, a layered ground with an elastic layer over a half-space and a cross-anisotropic ground are investigated. The wind-ground displacements predicted for continuously increasing rigidity indicate that such ground structures change the slope of the PSD of ground deformation. For layered grounds, the predicted PSD of ground deformation at very high frequencies is representative of the upper-layer elastic properties whereas the lower layer is responsible for the behavior at very low frequencies. The transition rate between two limits, or the slope of the PSD lines, is higher for layered grounds with thinner top layer. The predicted PSD of the ground deformation for transversely isotropic ground model with stiffer properties in the normal direction is linear like the isotropic model but with a larger radial to vertical displacement ratio. For the range of anisotropy investigated, this larger ratio is still not sufficient to explain the field observations. In conclusion, the more realistic ground models result in larger radial displacements but not enough to explain the field data. The hypothesis that the wind induced shear on the ground is larger than predicted from the viscosity of air and modeled wind velocity profile is strengthened and should be investigated. The inhomogeneous ground models show that the slope of the seismic wind noise PSD is a diagnostic for ground inhomogeneities given the naturally occurring wind noise.
Notlar:
School code: 0131
Tüzel Kişi Ek Girişi:
Mevcut:*
Yer Numarası | Demirbaş Numarası | Shelf Location | Lokasyon / Statüsü / İade Tarihi |
---|---|---|---|
XX(692649.1) | 692649-1001 | Proquest E-Tez Koleksiyonu | Arıyor... |
On Order
Liste seç
Bunu varsayılan liste yap.
Öğeler başarıyla eklendi
Öğeler eklenirken hata oldu. Lütfen tekrar deneyiniz.
:
Select An Item
Data usage warning: You will receive one text message for each title you selected.
Standard text messaging rates apply.