| 1. |
- 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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| 2. |
- 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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| 3. |
- 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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| 4. |
- 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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| 5. |
- 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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| 6. |
- 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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| 7. |
- Bucinskas, Paulius, et al.
(författare)
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Numerical modelling of ground vibration caused by elevated high-speed railway lines considering structure-soil-structure interaction
- 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. 2119-2130
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Konferensbidrag (refereegranskat)abstract
- Construction of high-speed railway lines has been an increasing trend in recent years. Countries like Denmark and Sweden plan to expand and upgrade their railways to accommodate high-speed traffic. To benefit from the full potential of the reduced commuting times, these lines must pass through densely populated urban areas with the collateral effect of increased noise and vibrations levels. This paper aims to quantify the vibrations levels in the area surrounding an elevated railway line built as a multi-span bridge structure. The proposed model employs finite-element analysis to model the bridge structure, including a multi-degree-of-freedom vehicle model and accounting for the track unevenness via a nonlinear contact model. The foundations are implemented as rigid footings resting on the ground surface, while the soil is modelled utilizing Green's function for a horizontally layered half-space. The paper analyses the effects of structure-soil-structure interaction on the dynamic behaviour of the surrounding soil surface. The effects of different soil stratification and material properties as well as different train speeds are assessed. Finally, the drawbacks of simplifying the numerical model, in order to reduce the complexity of the calculations, are determined.
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| 8. |
- 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. - 9781138386969 - 9780429426506 ; , 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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| 9. |
- 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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| 10. |
- Malmborg, Jens, et al.
(författare)
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Prediction models of free-field vibrations from railway traffic
- 2017
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Ingår i: COMPDYN 2017 : 6 th ECCOMAS Thematic Conference on Computational Methods in Structural Dynamics and Earthquake Engineering - 6 th ECCOMAS Thematic Conference on Computational Methods in Structural Dynamics and Earthquake Engineering. - Athens : Institute of Structural Analysis and Antiseismic Research School of Civil Engineering National Technical University of Athens (NTUA) Greece. ; , s. 4810-4820
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Konferensbidrag (refereegranskat)abstract
- Many cities experience an increasing population leading to a need for urban densification. In these cities, unused land close to railways will have to be developed with new residential and office buildings. The infrastructural demand will also increase, resulting in heavily trafficked roads and railways close to w here people work and live. Annoyance from traffic-induced vibrations and noise is expected to be a growing issue. To predict the level of vibration and noise in buildings caused by railway and road traffic, calculation models are needed.In the present pa per, a simplified prediction model is briefly described. This prediction model is based on the assumption that the ground and railway embankment can be described in an axisymmetric model , to provide the transfer functions between the track and the free-field . In the paper, the error that arise by assuming axisymmetric response is studied by comparing the response in a three-dimensional finite-element model. Transfer functions at several positions in the free-field are compared
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| 11. |
- Peplow, Andrew, et al.
(författare)
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Evaluating annoyance mitigation in the screening of train-induced noise and ground vibrations using a single-leaf traffic barrier
- 2021
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Ingår i: Science of the Total Environment. - : Elsevier BV. - 1879-1026 .- 0048-9697. ; 790
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Tidskriftsartikel (refereegranskat)abstract
- External sources such as traffic and construction work cause noise and vibration in nearby buildings, potentially annoying human residents. Today, almost every fifth European is harmfully affected by traffic noise and vibration. Wave barriers placed on or embedded within the soil between the source and the receiver can mitigate the transmission of ground vibration, and the airborne noise transmission can be reduced in a similar manner with a screen acting as a noise barrier. As a novel approach, the present work explores the efficiency of combining ground vibration and noise barriers into one. To this end, numerical experiments were performed by a semi-analytic finite-element method for ground vibration and the boundary-element method for sound propagation. This involved time-harmonic analyses carried out in order to study the performance of various configurations of barriers focusing on vertical barriers rigidly attached to the ground surface or embedded into the soil. Parametric analyses were conducted on the achieved vibration and noise mitigation with different types of ground-vibration barriers and noise barriers, respectively. The combined effect of the noise and ground vibration barriers were then assessed to investigate their potential for possibly reducing the negative impact on lineside residents. The aim of this work, though, is to highlight a metric, recently developed, which reports the probability on the number of residents who could be annoyed by intrusive railway noise and vibration. It is shown that a single structural-element can target a combined reduction of around 15% probability in annoyance to vibration levels combined with a 12 dB insertion loss which amounts to a 30% reduction in probability of annoyance due to railway traffic intrusive noise.
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| 12. |
- Peplow, Andrew T., et al.
(författare)
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Computation of axisymmetric vibration transmission using a well-conditioned system for elastic layers over a half–space
- 2019
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Ingår i: 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
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Konferensbidrag (refereegranskat)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.
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| 13. |
- Persson, Peter, et al.
(författare)
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Analysis of wind-induced vibrations in high-rise buildings
- 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. 7650-7661
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Konferensbidrag (refereegranskat)abstract
- Buildings are getting taller due to increased urbanisation and densification of cities. More advanced construction methods and the desire to construct impressive buildings is also supporting the trend. Due to their inherent slenderness resulting in low eigenfrequencies, these buildings are susceptible to wind-induced vibrations which can be highly disturbing for occupants. Already barely perceivable acceleration levels within the low-frequency range relevant to whole-body vibrations can cause nausea and discomfort, while high acceleration levels can cause alarm and fear amongst the occupants. The paper summarises acceptable acceleration levels in high-rise buildings (here referred to as buildings over 200 m in height) stated in different building codes and previous work on the subject. Accelerations of a high-rise building subjected to wind-loads are evaluated using a full numerical model and one reduced with Ritz-vectors and the results are compared. The paper focusses on wind-load dynamics in early stages of the design process, with an intent to give an indication of the dynamic properties of a building.
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| 14. |
- Persson, Peter, et al.
(författare)
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Effect of structural design on traffic-induced building vibrations
- 2017
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Ingår i: Procedia Engineering. - : Elsevier BV. - 1877-7058. ; 199, s. 2711-2716
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Tidskriftsartikel (refereegranskat)abstract
- Population growth and urbanization results in densified cities, where new buildings are being built closer to existing vibration sources, and new transportation systems are constructed closer to existing buildings. Potential disturbing vibrations are one issue to consider in planning urban environments and densification of cities. Vibrations can be annoying for humans but also for sensitive equipment in, for example, hospitals. In determining the risk for disturbing vibrations, the distance between the source and the receiver, the ground properties, and type and size of the building are governing factors. In the paper, a study is presented aiming at investigating the influence of various parameters of the building’s structural design on vibration levels in the structure caused by ground surface loads, e.g. traffic. Parameters studied are related to the type of construction material (if it would be a light or heavy structure), and to the slab thickness. The study is limited to the structural response at frequencies near the first resonance frequency of the soil. The finite element method is employed for discretizing the building structure that is coupled to a semi-analytical model considering a layered ground.
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| 15. |
- Persson, Peter, et al.
(författare)
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Efficient finite-element analysis of the influence of structural modifications on traffic-induced building vibrations
- 2018
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Ingår i: Numerical Methods in Geotechnical Engineering IX : roceedings of the 9th European Conference on Numerical Methods in Geotechnical Engineering (NUMGE 2018), June 25-27, 2018, Porto, Portugal - roceedings of the 9th European Conference on Numerical Methods in Geotechnical Engineering (NUMGE 2018), June 25-27, 2018, Porto, Portugal. - 9781138544468 - 9781351003612 ; 2, s. 1557-1564
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Konferensbidrag (refereegranskat)
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| 16. |
- Persson, Peter, et al.
(författare)
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How building adjacency affects occupant-perceivable vibrations due to urban sources : A parametric study
- 2019
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Ingår i: 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. 5610-5621
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Konferensbidrag (refereegranskat)abstract
- Urban densification, despite the economic and social opportunities it offers, brings with it challenges to the well-being of citizens. A direct effect of densification is the rise in noise- and vibration-producing sources, which can lead to both health and comfort issues. In determining the risk associated with excessive vibration levels, the distance between the source and the receiver or target building, the ground properties, and the building type, are all important factors. In this paper, we are concerned with the effect that adjacent buildings have on the prediction of the vibration levels in a residential building, caused by external ground surface loads. The parametric studies were conducted using a coupled finite element model of the ground and the buildings. The analyses were conducted in the frequency domain, and vibrational velocity levels were computed at the receiver building in order to assess how building adjacency affects the receiving building’s vibrational response.
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| 17. |
- Persson, Peter, et al.
(författare)
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Improved low-frequency performance of cross-laminated timber floor panels by informed material selection
- 2021
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Ingår i: Applied Acoustics. - : Elsevier BV. - 0003-682X. ; 179
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Tidskriftsartikel (refereegranskat)abstract
- The paper demonstrates improved structural low-frequency vibroacoustic performance of cross-laminated timber (CLT) floor panels by informed selection of the wood material. The use of wood species and strength classes that are not traditionally assigned to CLT panels was investigated in order to study their influence on dynamic characteristics and vibroacoustic response metrics. The potential of each of the orthotropic material properties to alternate the vibration response was examined to determine the governing parameters of the low-frequency vibroacoustic performance. The effects on transfer mobility response functions, and eigenfrequencies and mode shapes were used for a rigorous performance study of the panels. It was found that using laminations with stiffness properties typical for hardwoods ash, beech, and birch can significantly improve the performance of a CLT floor panel, and they outperform laminations of typical softwood strength classes.
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| 18. |
- Persson, Peter, et al.
(författare)
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Strategy for predicting railway-induced vibrations in buildings
- 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. 2098-2109
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Konferensbidrag (refereegranskat)abstract
- Urban densification is a way of accommodating population growth. Land adjacent to railways is used for constructing residences and other buildings, and new tramway systems are planned. Under these circumstances, nearby buildings will be exposed to vibrations and noise that may become a nuisance for the residents. It is necessary, even at an early stage of planning, to assess the extent of the vibrations and state requirements for the building in order to avoid costly changes at later stages. Ground vibration induced by railway traffic is studied in the paper. The aim is to develop a strategy for predicting vibrations in nearby buildings in an early stage of the building process. The strategy is based on that there is a fairly good knowledge of the properties of the ground and that some on-site vibration measurements are made. By combining these with finite-element analysis, the vibration level in typical buildings can be predicted. Design of building foundations and structural design can then be addressed. Field vibration measurements along railway tracks as well as at built-up areas have been carried out. Conclusions from the measurements and numerical simulations are discussed to establish a strategy for predicting railway-induced vibrations.
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