| 1. |
- Andersen, Lars V., et al.
(author)
-
Mitigation of ground vibration from pile driving by circular arrays of rigid blocks placed on the ground surface
- 2020
-
In: EURODYN 2020 - 11th International Conference on Structural Dynamics, Proceedings. - 2311-9020. - 9786188507210 ; 2, s. 2966-2984
-
Conference paper (peer-reviewed)abstract
- Ground vibration associated with pile driving causes annoyance to inhabitants of the neighbouring environment and may possibly lead to damage on existing structures in the proximity of a construction site. Vibration mitigation near the source can reduce the problem. The paper investigates the effect of circular arrays of blocks, placed on the ground surface around the position at which the pile is driven. A semi-analytical model of a layered soil has been used for the analysis, and the blocks have been modelled as monolithic structures, accounting for the full structure-soil-structure interaction. Two different sites have been studied: a layered soil with three metres of soft sand over a half-space of till, and a five metres deep layer of soft clay overlying a half-space of lime. The block arrays consist of one to three concentric rings with radii 4, 8, and 12 m, respectively. The rings contain 6, 12, and 24 blocks, respectively, and the size of the blocks have been scaled such that each ring has the same total mass. The pile has not been modelled explicitly; instead vertical excitation has been applied in different depts over a circular area corresponding to the cross section of a pile. For the considered cases it has been found that an array of blocks, shaped as a "Stonehenge ", may provide significant mitigation of the ground vibration level in a receiver zone placed 20-40 m from the pile. When a load is applied within the soft tops oil layer, the array provides an insertion loss in the order of 5-20 dB, depending on the size of the blocks and the configuration of the arrays. For loads applied deeper in the soil, within the stiffer half-space, the insertion loss is small and may in some situations be negative. However, this must be seen in the context that the transfer mobility in the reference state without the blocks, i.e. the greenfield, is low when the load is applied within the stiff half-space.
|
|
| 2. |
- Andersen, Lars V., et al.
(author)
-
Mitigation of ground vibrations by circular arrays of rigid blocks
- 2019
-
In: COMPDYN 2019 - 7th International Conference on Computational Methods in Structural Dynamics and Earthquake Engineering, Proceedings. - 2623-3347. - 9786188284470 ; 2, s. 3422-3447
-
Conference paper (peer-reviewed)abstract
- Pile driving and other activities in the built environment cause ground vibration at low frequencies. This may result in annoyance to people as well as damage to civil structures. It is known that masses added on the ground surface can have an impact on the vibration levels in the surrounding environment. Hence, employing a semi-analytical model for rigid blocks on the surface of a layered ground, this paper investigates whether circular arrays of such blocks can be used as a means of vibration mitigation. The frequency range 0–80 Hz is considered, since this is relevant to whole-body vibrations of humans as well as the fundamental modes of resonance in building elements, e.g., floors and walls. Two different soil profiles are analysed: a soft dry sand layer over a till half-space and a soft wet clay layer over a lime half-space. Further, three configurations of the block arrays are taken into consideration, and for the first soil profile also the height of the blocks is varied to test its influence on the insertion loss in a zone 20–40 m away from the source. The aim is to quantify the overall insertion loss that can be expected using the proposed methodology. Further, the variation in insertion loss caused by changes in the block array configuration is examined.
|
|
| 3. |
- Bonfiglio, P., et al.
(author)
-
Aspects of computational vibration transmission for sandwich panels
- 2007
-
In: Journal of Sound and Vibration. - : Elsevier BV. - 0022-460X .- 1095-8568. ; 303:3-5, s. 780-797
-
Journal article (peer-reviewed)abstract
- This paper considers elastic wave propagation and vibration transmission in lightweight composite structures. Specifically a spectral finite element method (SFEM) is developed as an effective numerical tool for the analysis of wave motion in uniform laminated elastic media. In short, SFEM combines a standard finite element method in the direction of layering together with analytical solutions for the remaining direction. This partial discretization leads naturally, via the variational formulation, to dispersion relations for uniform sections of built-up laminates and thus provides valuable information for a wave propagation analysis. Dynamic responses of the vibrating structures are also investigated and numerical simulations compared against a standard finite element method. The predicted transfer accelerances obtained for the steel beam and two sandwich panels are compared with measured data from laboratory experiments.
|
|
| 4. |
- Bonfiglio, P., et al.
(author)
-
Normal incidence transmission loss of sandwich structures in a plane wave tube
- 2006
-
In: International Congress on Sound and Vibration 2006. - 9781627481502 ; , s. 317-324
-
Conference paper (peer-reviewed)abstract
- The Transmission Loss of different kind of layered structures is investigated by means of a four microphone technique in a plane wave tube. By using the decomposition technique, incident, reflected and transmitted contributions are separated and transmission coefficient is easily calculated. In this paper a single measurement approach based on transfer matrix, taking into account reflection contribution from the end termination, is presented. Results are discussed and compared with similar techniques and with the two-load method.
|
|
| 5. |
- Bonfiglio, P., et al.
(author)
-
Spectral element and experimental analysis of lightweight sandwich structures
- 2006
-
In: 13th International Congress on Sound and Vibration 2006. - 9781627481502 ; , s. 2240-2247
-
Conference paper (peer-reviewed)abstract
- The dynamic response of the vibrating structures are studied with the standard finite element method against the more computationally efficient spectral finite element method. First a simple beam structure is modelled with the standard method and newly developed spectral elements; which has the advantage that dispersion relations for all beam structures may be developed. Some numerical examples are given to illustrate and validate the developed method and studies of the measured responses of structures that may be used for vehicle panels are compared.
|
|
| 6. |
- Chandler-Wilde, S. N., et al.
(author)
-
A boundary integral equation formulation for the Helmholtz equation in a locally perturbed half-plane
- 2005
-
In: Zeitschrift für angewandte Mathematik und Mechanik. - : Wiley. - 0044-2267 .- 1521-4001. ; 85:2, s. 79-88
-
Journal article (peer-reviewed)abstract
- In this paper we study the application of boundary integral equation methods to the solution of the Helmholtz equation in a locally perturbed half-plane with Robin or impedance boundary conditions. This problem models outdoor noise propagation from a cutting onto a surrounding flat plane, and also the harbour resonance problem in coastal engineering. We employ Green's theorem to derive a system of three coupled integral equations. The three unknowns are the pressure on the boundary of the disturbance and the pressure and its normal derivative on the interface with the upper half-space. We prove that the integral equation formulation has a unique solution at all wavenumbers by proving equivalence of the boundary value problem and the integral equation formulation and proving uniqueness of solution for the boundary value problem.
|
|
| 7. |
- Peplow, Andrew T., et al.
(author)
-
Computation of axisymmetric vibration transmission using a well-conditioned system for elastic layers over a half–space
- 2019
-
In: COMPDYN 2019 - 7th International Conference on Computational Methods in Structural Dynamics and Earthquake Engineering, Proceedings. - Athens : Institute of Structural Analysis and Antiseismic Research School of Civil Engineering National Technical University of Athens (NTUA) Greece. - 2623-3347. - 9786188284456 ; 3, s. 4548-4556
-
Conference paper (peer-reviewed)abstract
- In the context of range-independent solid media, we propose a well-conditioned dynamic stiffness matrix for an elastic layer sitting over an elastic half-space. This formulation overcomes the well-known problem of numerical ill-conditioning when solving the system of equations for deep-layered strata. The methodology involves the exact solutions of transformed ordinary differential equations in the wavenumber domain, namely a projection method based on the transformed equations with respect to the depth coordinate. By re-arranging the transformed equations, the solutions remain numerically well-conditioned for all layer depths. The inverse transforms are achieved with a numerical quadrature method and the results presented include actual displacement fields in the near-field of the load in plane-strain and three-dimensional axisymmetric cases. Verification against finite element method (FEM) calculations demonstrates the performance and complexity of the two approaches.
|
|
| 8. |
- Peplow, Andrew T.
(author)
-
Numerical predictions of sound propagation from a cutting over a road-side noise barrier
- 2005
-
In: Journal of Computational Acoustics. - 0218-396X. ; 13:1, s. 145-162
-
Journal article (peer-reviewed)abstract
- A boundary integral equation is described for the prediction of acoustic propagation from a monofrequency coherent line source in a cutting with impedance boundary conditions onto surrounding flat impedance ground. The problem is stated as a boundary value problem for the Helmholtz equation and is subsequently reformulated as a system of boundary integral equations via Green's theorem. The numerical solution of the coupled boundary integral equations by a simple boundary element method is then described. Predictions of A-weighted insertion losses for a traffic noise spectrum are made illustrating the effects of depth of the cutting and the profile of the associated noise barrier.
|
|
| 9. |
- Peplow, Andrew T.
(author)
-
On the efficiency of screens near roadside cuttings
- 2006
-
In: Journal of Sound and Vibration. - : Elsevier BV. - 0022-460X .- 1095-8568. ; 298:4-5, s. 982-1000
-
Journal article (peer-reviewed)abstract
- The prediction of acoustic propagation from a monofrequency coherent line source in a cutting with impedance boundary conditions over a noise-screen onto surrounding flat grassland is presented. It is well known that over flat ground the spectra for single-noise screens have significant marked differences for propagation over absorbing ground where the screen obstructs surface wave attenuation over the absorbing ground cover. The aim here is to extend the study of this phenomenon for screens adjacent to cuttings or dips surrounded by absorbing ground. The study is based on a numerical model using boundary element techniques that enables the excess attenuation and insertion loss for various noise barriers and cuttings of complex profile and surface cover to be calculated. The model is applied to single-foundation noise barriers to which additional absorbent or rigid side-panels are added to create profiles and a double-barrier configuration is also studied. Spectra of insertion loss, change in insertion loss and excess attenuation results for a broadband traffic-source are presented. It is concluded that "multiple-edged" barriers only show a minor increase in acoustic efficiency over simple vertical screens for a noise source located in perturbed flat ground conditions such as a cutting; in addition it is shown that a screen placed close to the source shows sign of partial improvement.
|
|
| 10. |
- Peplow, Andrew T., et al.
(author)
-
Prediction and validation of traffic vibration reduction due to cement column stabilization
- 2007
-
In: Soil Dynamics and Earthquake Engineering. - : Elsevier BV. - 0267-7261 .- 1879-341X. ; 27:8, s. 793-802
-
Journal article (peer-reviewed)abstract
- The transmission and reduction of vibrations in the far-field of the surface of the ground due to a surface load is investigated theoretically and validated with given field measurement data. The performance of a given stabilization column, located directly underneath the load, at a number of receiver positions is studied and-measured in terms of insertion loss. A numerical model is presented, which enables the wave-field in the region of the column to be determined, based on an integral equation formulation of the problem which is solved using a boundary element approach. It is shown that the column has a beneficial effect at low frequencies especially in certain frequency bandwidths and is validated with field data. However, when the Rayleigh wavelength becomes short compared with the depth and width of the column adverse effects occur at some frequencies which are also observed in the far-field. Various depths of columns and material properties of the surrounding soil medium are studied and results presented so that some preliminary physical conclusions may be derived.
|
|
