| 1. |
- Andersen, Lars Vabbersgaard, et al.
(författare)
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Influence of foundation type and soil stratification on ground vibration - A parameter study
- 2016
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Ingår i: Proceedings of the INTER-NOISE 2016 - 45th International Congress and Exposition on Noise Control Engineering: Towards a Quieter Future. ; , s. 7613-7622
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Konferensbidrag (refereegranskat)abstract
- Vibration of machinery and construction work are major sources of noise and vibration pollution in the urban environment. The frequencies dominating the vibration, and the distances over which it spreads via the ground, depend on the source. However, soil stratification and foundation type have a significant influence. Thus, in order to achieve fair accuracy in the prediction of ground vibration caused by sources vibrating on a foundation, accurate models of the ground and foundation may be required. However, for assessment of vibration in the design phase, simple models may be preferred. The paper provides a parameter study regarding the influence of soil stratification and foundation type on the ground vibration at different distances away from the source. Especially, vibration levels caused by sources placed on surface footings and piles are compared, employing a three-dimensional numerical model. Piles of different length are included in order to analyze the differences that can be expected regarding shaft-bearing and end-bearing piles. The paper provides insight into the significance of modelling the correct foundation structure and soil stratification and discusses the differences related to vibration near a source and at longer distances away from the source. Based on this, guidelines for model simplifications are given.
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| 2. |
- Andersen, Lars Vabbersgaard, et al.
(författare)
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Influence of furniture on the modal properties of wooden floors
- 2020
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Ingår i: Model Validation and Uncertainty Quantification, Volume 3 - Proceedings of the 37th IMAC, A Conference and Exposition on Structural Dynamics 2019. - Cham : Springer International Publishing. - 9783030120740 ; , s. 197-204
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Konferensbidrag (refereegranskat)abstract
- Structure-borne vibration and low-frequency re-radiated noise from internal and external sources cause annoyance for inhabitants in dwellings. A key parameter in the prediction of vibration and noise levels is the modal parameters of the floors in a building, since vibration and sound levels increase when natural frequencies of the floor coincide with the excitation frequencies of a source, e.g. monoharmonic vibration of unbalanced rotating machinery and appliances or HVAC system—or traffic induced ground vibration propagating into the building. This paper has focus on wooden floors built as an assembly of particleboard and timber joists. Such floors constitute horizontal divisions in many dwellings—both older, traditional buildings and new lightweight buildings. The analysis concerns the impact of furniture placed on a floor with otherwise known properties. Given the small mass of a traditional wooden floor, the presence of furniture can be expected to change the modal properties of the floor significantly. The finite-element model, developed for the present analyses, accounts for uncertainty in the position of the furniture, and the analysis addresses the importance of the elevation of the mass above the floor regarding the natural frequencies and the related modes of vibration.
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| 3. |
- Andersen, Lars Vabbersgaard, et al.
(författare)
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Mitigating ground vibration by periodic inclusions and surface structures
- 2016
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Ingår i: Proceedings of the INTER-NOISE 2016 - 45th International Congress and Exposition on Noise Control Engineering: Towards a Quieter Future. ; , s. 7469-7480
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Konferensbidrag (refereegranskat)abstract
- Ground vibration from traffic is a source of nuisance in urbanized areas. Trenches and wave barriers can provide mitigation of vibrations, but single barriers need to have a large depth to be effective - especially in the low-frequency range relevant to traffic-induced vibration. Alternatively, periodic repetitions of mass, stiffness or both in an infinite structure lead to so-called stop bands in the frequency domain. Harmonic loads applied within these stop bands will not induce propagation of energy through the structure, i.e. the energy stays within a nearfield surrounding the source. Less well-defined behavior can be expected for transient loads and finite structures. However, some mitigation may occur. The paper aims at quantifying the mitigation effect of nearly periodic masses placed on the ground surface using two approaches: a small-scale laboratory model and a three-dimensional finite-element model. The laboratory model employs soaked mattress foam placed within a box to mimic a finite volume of soil. The dynamic properties of the soaked foam ensure wavelengths representative of ground vibration in small scale. Comparison of the results from the two models leads to an assessment of the mitigation that can be expected in a real project compared to the mitigation predicted by a numerical model.
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| 4. |
- Andersen, Lars V., et al.
(författare)
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Mitigation of ground vibration from pile driving by circular arrays of rigid blocks placed on the ground surface
- 2020
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Ingår i: EURODYN 2020 - 11th International Conference on Structural Dynamics, Proceedings. - 2311-9020. - 9786188507210 ; 2, s. 2966-2984
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Konferensbidrag (refereegranskat)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.
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| 5. |
- Andersen, Lars V., et al.
(författare)
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Mitigation of ground vibrations by circular arrays of rigid blocks
- 2019
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Ingår i: COMPDYN 2019 - 7th International Conference on Computational Methods in Structural Dynamics and Earthquake Engineering, Proceedings. - 2623-3347. - 9786188284470 ; 2, s. 3422-3447
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Konferensbidrag (refereegranskat)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.
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| 6. |
- Andersen, Lars Vabbersgaard, et al.
(författare)
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Probabilistic assessment of ground-vibration transfer in layered soil
- 2018
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Ingår i: Numerical Methods in Geotechnical Engineering IX : Proceedings of the 9th European Conference on Numerical Methods in Geotechnical Engineering (NUMGE 2018), June 25-27, 2018, Porto, Portugal - Proceedings of the 9th European Conference on Numerical Methods in Geotechnical Engineering (NUMGE 2018), June 25-27, 2018, Porto, Portugal. - 9781351003612 - 9781138544468 ; 2, s. 1577-1586
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Konferensbidrag (refereegranskat)
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| 7. |
- Andersen, Lars Vabbersgaard, et al.
(författare)
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Variation in models for simple dynamic structure–soil–structure interaction problems
- 2017
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Ingår i: Procedia Engineering. - : Elsevier BV. - 1877-7058. ; 199, s. 2306-2311
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Konferensbidrag (refereegranskat)abstract
- To account for dynamic cross-coupling of structures via the soil, a computational model must be accurate enough to provide the correct overall behaviour of the scattered wave field. However, simplicity is also important when a model should be used for design purposes, especially in the early design stages and feasibility studies. The paper addresses the accuracy of simple models in which an array of structures is simplified into blocks placed on the ground surface or embedded within the soil. Comparisons are made between models that account or do not account, in a proper manner, for the inertia and embedment of the structures. Especially, the limitations of simplified models are discussed regarding their capability to quantify the insertion loss accurately.
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| 8. |
- Frier, Cristian, et al.
(författare)
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Flooring-systems and their interaction with furniture and humans
- 2017
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Ingår i: Procedia Engineering. - : Elsevier BV. - 1877-7058. ; 199, s. 146-151
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Tidskriftsartikel (refereegranskat)abstract
- Flooring-system designs may be sensitive in terms of their vibrational performance due the risk that serviceability-limit-state problems may be encountered. For evaluating the vibrational performance of a flooring system at the design stage, decisions must be made by the engineer in charge of computations. Passive humans and/or furniture are often present on a floor. Typically, these masses and their way of interacting with the floor mass are ignored in predictions of vibrational behaviour of the flooring system. Utilizing a shell finite-element model, the paper explores and quantifies how non-structural mass can influence central parameters describing the dynamic behaviour of the flooring system with focus on elevated non-structural mass.
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| 9. |
- Lim, Hyeong Uk, et al.
(författare)
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A surrogate model to describe uncertainties in wood floor modal frequencies
- 2019
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Ingår i: Advances in Engineering Materials, Structures and Systems : Innovations, Mechanics and Applications - Proceedings of the 7th International Conference on Structural Engineering, Mechanics and Computation, 2019 - Innovations, Mechanics and Applications - Proceedings of the 7th International Conference on Structural Engineering, Mechanics and Computation, 2019. - : CRC Press. - 9780429426506 - 9781138386969 ; , s. 121-126
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Konferensbidrag (refereegranskat)abstract
- Wooden multi-story buildings have increased their market share in Europe over the last decades, mainly due to their relatively small carbon footprint and rapid onsite construction. Compared to more conventional heavy concrete buildings, wooden buildings are more sensitive to dynamic loads at low frequencies. Moreover, the dynamic response is generally more difficult to predict. This is, for example, due to the variability in the material properties of wood. Since wood is a natural material, local variations in performance occur, even if selected members are taken from the same batch. Also, the cut and treatment of individual members have an impact, and material properties can vary with time due to changing moisture content and aging effects. In this study, we investigate the effect of variability in material properties of joists on the dynamic modal characteristics of wood floors with the help of surrogate models, constructed using polynomial chaos expansion (PCE). These surrogate models are based on computations that use a dynamic reduced-order finite-element (FE) model, calibrated to produce modal outputs consistent with floor vibration experiments. Uncertainty in modal frequencies of the wood floor systems based on the PCE surrogate models is consistent with that found using the FE model in Monte Carlo simulations, which serve to define the “truth” model. However, PCE surrogate models offer significant reduction in computation time compared to FE models, when uncertainty in dynamic behavior needs to be quantified.
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| 10. |
- Lim, Hyeong Uk, et al.
(författare)
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Uncertainty quantification of wood floor system modal frequencies resulting from variable densities in members
- 2023
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Ingår i: Structures. - 2352-0124. ; 53, s. 1425-1434
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Tidskriftsartikel (refereegranskat)abstract
- Low-frequency vibration in a multi-story wood building is of concern because failure in mitigation of such vibration may lead to occupant discomfort. Ultimately, it may cause damage to their health. Variability in material properties of the members of a wooden floor system significantly influences vibration response characteristics such as eigenfrequencies and mode shapes. In this study, we investigate the uncertainty in low-frequency characteristics of a selected wood floor system, resulting from uncertainty in the members’ material properties. We use a surrogate model developed using polynomial chaos expansion, based on a few training samples computed using a finite element model of an experimental-scale structure comprised of seven load-bearing joists of spruce. We estimate the hyperparameters needed for accurate surrogate model development and, with these, we predict probability distributions for each of the floor-system modal frequencies. Also, we perform local and global sensitivity analyses to assess how material property variation affects the modal frequencies. Results confirm the accuracy and efficiency of the developed surrogate models in prediction of the modal frequencies, resulting from uncertainty in wood material properties. The accuracy of the results is comparable to those based on more expensive Monte Carlo simulation.
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