| 1. |
- Deckner, Fanny, et al.
(författare)
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Sheet pile behavior during vibratory driving : numerical study based on a field test
- 2017
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Ingår i: Soil Dynamics and Earthquake Engineering. - 0267-7261 .- 1879-341X.
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Tidskriftsartikel (refereegranskat)abstract
- Vibrations due to sheet pile driving are a problem in many urban areas today. Increased knowledgeof the vibration transfer process from source to nearby objects is important in order to enableminimization of induced vibrations. The transfer of vibrations from sheet pile to soil is dependent onthe sheet pile behaviour during driving. This paper presents a 3D finite element study of thebehaviour of a vibratory driven sheet pile, complementing results from a full-scale field test. Thefinite element model accounts for strain dependent soil stiffness using an equivalent linear soilmodel. The conclusion is that the sheet pile bends considerably during driving with eccentricclamping. Furthermore, it is shown that the bending mode is similar irrespective of sheet pilepenetration depth.
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| 2. |
- Martakis, Panagiotis, et al.
(författare)
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A centrifuge-based experimental verification of Soil-Structure Interaction effects
- 2017
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Ingår i: Soil Dynamics and Earthquake Engineering. - : Elsevier. - 0267-7261 .- 1879-341X. ; 103, s. 1-14
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Tidskriftsartikel (refereegranskat)abstract
- A series of prototype dynamic centrifuge experiments is carried out to investigate the influence of soil properties and structural parameters on the Soil Structure Interaction (SSI) effect. Established analytical models are herein experimentally verified, and are proven accurate in estimating the system's natural frequency characteristics. It is observed that period elongation is strongly correlated to the relative superstructure-foundation stiffness. Although the present study deals exclusively with the small-strain near-linear range, the experimental response indicates occurrence of nonlinearity. The identified damping results remarkably larger than its analytical estimate and proves highly strain-dependent, raising questions on the reliability of existing analytical methods in capturing the actual dissipation mechanisms. An extended experimental dataset is formed under realistic stress and strain soil conditions, and is implemented, for the first time, for verification of existing analytical models offering valuable insight into the theory and serving as a benchmark for engineering practice.
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| 3. |
- Mihaylov, Aleksandar, et al.
(författare)
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Approximate analytical HVSR curve using multiple band-pass filters and potential applications
- 2019
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Ingår i: Soil Dynamics and Earthquake Engineering. - : Elsevier. - 0267-7261 .- 1879-341X. ; 127
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Tidskriftsartikel (refereegranskat)abstract
- The Nakamura method, which utilizes the Horizontal to Vertical Spectral Ratio (HVSR) analysis, is widely used for seismic microzonation studies. The HVSR is an easy tool for estimation of site response resonances based on recorded ambient noise; however, it gives amplifications at resonant frequencies that are poorly correlated to the actual amplifications during strong ground motion.Generally, the site response, including any resonant effects, depends on the amplitude, frequency and duration of ground motion. An approach was proposed previously by McGuire [1], in which the transfer function of the soil response was approximated as a Single Degree of Freedom (SDOF) oscillator with one resonant frequency, obtained from the maximum in HVSR. A new approach is developed here, in which the entire HVSR curve is approximated by a manageable set of parallel band-pass resonators. Each individual oscillator is defined by three parameters: center frequency, gain, and steepness (Q factor). This approximation allows for the development and use of an analytical model of the HVSR curve.The application of the new approach is demonstrated on data recorded by the stations of the Southern Ontario Seismic Network (SOSN/Polaris), which have well studied characteristics and site response [2,3]. Data collected at each site consists of noise recordings to obtain the HVSR, as well as earthquake records. The analytical HVSR curves for each station are used to remove the site effect component from the recorded seismograms.
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| 4. |
- Olafsdottir, Elin Asta, et al.
(författare)
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Combination of dispersion curves from MASW measurements
- 2018
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Ingår i: Soil Dynamics and Earthquake Engineering. - : Elsevier Ltd. - 0267-7261 .- 1879-341X. ; 113, s. 473-487
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Tidskriftsartikel (refereegranskat)abstract
- Multichannel analysis of surface waves (MASW) is a seismic exploration method for determination of near-surface shear wave velocity profiles based on analysis of horizontally travelling Rayleigh waves. This paper aims to propose a methodology and recommendations for combining dispersion data from several multichannel records. The dispersion curves are added up within logarithmically spaced wavelength intervals and the uncertainty of the mean phase velocity estimates is evaluated by using classical statistics and the bootstrap. The results indicate that combining multiple dispersion curves, which have been gathered by receiver spreads of different lengths (but with the same midpoint), can increase the investigation depth of the survey, improve its resolution at shallow depth and overall improve the reliability of the results as compared to the use of a single record. Moreover, the uncertainty of the combined mean dispersion curve can be determined and further used to present the shear wave velocity profile with upper and lower boundaries.
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| 5. |
- Zangeneh, Abbas, 1980-, et al.
(författare)
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Fundamental Modal Properties of Simply Supported Railway Bridges Considering Soil-Structure Interaction Effects
- 2019
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Ingår i: Soil Dynamics and Earthquake Engineering. - : Elsevier. - 0267-7261 .- 1879-341X. ; 121, s. 212-218
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, a simplified discrete model for calculating the modal parameters of the fundamental vertical mode of a simple beam on viscoelastic supports is proposed. Exact closed-form expressions for the fundamental natural frequency and modal damping ratio of the aforementioned coupled system are derived, as a function of the beam geometry and the foundation impedances. Using this model, the effect of the dynamic stiffness and dissipation capacity of the foundation-soil system on the modal characteristics of the fundamental vertical mode of the railway beam bridges is investigated and discussed. The proposed closed-form expressions, in combination with the impedance functions of different foundation-soil systems, can clarify the main features of dynamic SSI analysis of the railway beam bridges and lead to review the recommended modal damping ratios in the code provisions and design manuals.
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| 6. |
- Yuan, Z. H., et al.
(författare)
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An analytical model for calculating vibrations from twin tunnels in a saturated poroelastic half-space
- 2019
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Ingår i: Soil Dynamics and Earthquake Engineering. - : Elsevier BV. - 0267-7261. ; 120, s. 23-27
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Tidskriftsartikel (refereegranskat)abstract
- In this paper a semi-analytical solution is proposed for modelling vibrations from a twin tunnel in a saturated poroelastic half-space. The twin tunnels are simulated as two hollow cylinders made of a viscoelastic material. The half-space containing the two circular cavities is described as a two-phase poroelastic material. The wave field in the half-space with two cylindrical cavities is taken as the combination of down-going plane waves from the ground surface and outgoing cylindrical waves from each tunnel. With the help of transformation and translation properties of the plane and cylindrical waves the boundary condition at each scattering surface can be expressed with the appropriate coordinates. Numerical results suggest that the reflection effect of the ground surface has limited influence on the response of the tunnels, but has a greater influence on the free-field response near the surface. Compared with the single tunnel solution, the wave field above the twin tunnels is greatly distorted.
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| 7. |
- Yuan, Z. H., et al.
(författare)
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Analytical solution for calculating vibrations from twin circular tunnels
- 2019
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Ingår i: Soil Dynamics and Earthquake Engineering. - : Elsevier BV. - 0267-7261. ; 117, s. 312-327
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Tidskriftsartikel (refereegranskat)abstract
- The calculation of vibrations from a single tunnel embedded in a full- or half-space due to underground moving trains has been well studied in the literature. A common assumption made in the majority of vibration prediction models is to neglect the presence of a neighboring tunnel, however, twin tunnels are a particularly preferred construction for urban underground railways with one as the inbound tunnel and the other as the outbound tunnel. The neglect of the interaction between twin tunnels may lead to inaccuracies of the calculation of vibrations from underground railways. The present paper proposes a novel analytical solution, which takes the multiple scattering effects between the two tunnels into account. The two tunnels are modelled as elastic hollow cylinders and the soil surrounding the tunnels as an elastic, homogeneous full-space containing two cylindrical cavities. The wave field in the full-space with two cavities consists of outgoing waves from each tunnel outside the two scattering surfaces while the wave field in the tunnel wall is a combination of outgoing and regular cylindrical waves. The translation of the outgoing cylindrical wave functions is required to satisfy the boundary conditions at the other tunnel. Numerical results show that there are two critical velocities for a twin tunnel in a full-space system, both of which are around the shear wave velocity of the soil. Through comparison with the single tunnel solution, the addition of a second tunnel at different separation distances and angles has a significant influence on the soil response, especially in the high frequency range, but the response at the tunnel with the source is not much affected.
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| 8. |
- Yuan, Z. H., et al.
(författare)
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The wave function method for calculation of vibrations from a twin tunnel in a multi-layered half-space
- 2019
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Ingår i: Soil Dynamics and Earthquake Engineering. - : Elsevier BV. - 0267-7261. ; 125
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Tidskriftsartikel (refereegranskat)abstract
- The ground vibrations due to underground moving trains cause disturbances to nearby buildings and their residents, which has been viewed as an important environmental issue. Various numerical or semi-analytical models are used to calculate the vibrations from underground railways, however, most of the prediction models adopt a single tunnel-soil system for modelling vibrations from underground trains and neglect the influence of a neighboring tunnel. In this paper, a semi-analytical wave function method is proposed for modelling vibrations from twin tunnels in a multi-layered viscoelastic and poroelastic half-space. The two tunnels are modelled as two hollow cylinders while the surrounding soil is modelled as a multi-layered half-space containing two circular cavities. The vibrations of the tunnel walls are taken as a superposition of outgoing and regular cylindrical waves. The wave field in the soil layer containing two cavities consists of down-going and up-going plane waves and cylindrical waves propagating outwards from each tunnel. In the wave function method, the transformation and translation of the plane and cylindrical waves make it possible to apply the boundary conditions at the scattering surfaces. Numerical results show that the half-space model predicts higher surface vibrations than a full-space model at equivalent surface locations. When the second tunnel is added near a deeper existing tunnel, a wider range of the free-field response above the two tunnels is significantly changed, however, the response below twin tunnels is less affected. If the separation distance between the two tunnels is smaller than five times the tunnel diameter, a twin tunnel model in a half-space is more suitable for an accurate vibration prediction at the ground surface. The cutoff effect of the rigid base is more visible for shallow bedrock at lower frequencies while the influence of the bedrock is quite limited at higher frequencies.
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