| 1. |
- 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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| 2. |
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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. |
- Andersson, Linus, et al.
(författare)
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Efficient nonlinear reduced order modeling for dynamic analysis of flat structures
- 2023
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Ingår i: Mechanical Systems and Signal Processing. - : Elsevier BV. - 0888-3270. ; 191
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Tidskriftsartikel (refereegranskat)abstract
- In the present paper, strategies for reduced order modeling of geometrically nonlinear finite element models are investigated. Simulation-free, non-intrusive approaches are considered, which do not require access to the source code of a finite element program (e.g., proprietary knowledge). Our study focus on but is not restricted to flat structures. Reduction bases are generated using bending modes and the associated modal derivatives, which span the additional subspace needed for an adequate approximation of the geometrically nonlinear response. Moreover, the reduced nonlinear restoring forces are expressed as third order polynomials in modal coordinates. Consequently, the reduced systems can be effectively solved using time-integration schemes involving only the reduced coordinates. A bottleneck in the non-intrusive methods is typically the computational effort for precomputing the polynomial coefficients and generating the reduction basis. In this regard, we demonstrate that modal derivatives have several useful properties. In particular, the modal derivatives essentially provide all the information needed for generating the polynomial coefficients for the in-plane coordinates. For condensed systems, which ignores the inertia of the in-plane modes, we show that the modal derivatives can be used effectively for recovering the in-plane displacements. Based on these findings, we propose a methodology for generating reduced order models of geometrically nonlinear flat structures in a computationally efficient manner. Moreover, we demonstrate that the concepts extend also to curved structures. The modeling techniques are validated by means of numerical examples of solid beam models and continuously supported shell models. The computational efficiency of the proposed methodology is evaluated based on the number of static evaluations needed for identifying the polynomial coefficients, as compared to the state-of-the-art methods. Furthermore, strategies for efficient time integration are discussed and evaluated.
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| 5. |
- Andersson, Linus, et al.
(författare)
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Model reduction for structures subjected to blast loading by use of dynamic substructuring
- 2020
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Ingår i: EURODYN 2020 - 11th International Conference on Structural Dynamics, Proceedings. - 2311-9020. - 9786188507210 ; 2, s. 2544-2564
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Konferensbidrag (refereegranskat)abstract
- In the present study, strategies are developed to enable time-efficient models for structures subjected to blast loading, appropriate for use in a structural design process. Dynamic sub structuring is employed to obtain reduced models with localized nonlinearities, such as predefined plastic hinges in a beam column structure. The parts of the substructures that remains linear elastic are modeled by Ritz-vectors whereas parts with a nonlinear response are retained as physical degrees-of-freedom. Furthermore, a time-stepping method is presented that is shown to be suitable for reduced models including local and predefined rigid-plastic behavior. The proposed methodology is applied and demonstrated in a numerical example of a concrete frame structure. Both the well-established Craig-Bampton method and reduction bases enriched by so-called correction modes are evaluated. For the load case studied, it is shown that the standard Craig-Bampton technique is suitable for reducing the substructures. Furthermore, it is shown that only a few Ritz-vectors are needed to sufficiently describe the deformation of the structure. However, additional modes are needed to ensure an accurate representation of the interface forces between the substructures.
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| 6. |
- Andersson, Linus, et al.
(författare)
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Reduced order modeling for the dynamic analysis of structures with nonlinear interfaces
- 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. 2395-2406
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Konferensbidrag (refereegranskat)abstract
- In the present paper, linear substructures with nonlinearities localized at their interfaces, such as the joints in a beam structure, are studied. By subdivision of the total structure into substructures, reduced subsystems are obtained by component mode synthesis. Nonlinear elements are introduced at supports or between substructures. A numerical example is presented where a beam subjected to blast loading is studied. The influence of the nonlinear behavior as well as the number of retained fixed-interface normal modes in the reduced subsystems are evaluated. The response is also compared to the response of equivalent single-degree-of-freedom systems, which are frequently employed in blast load design calculations. For the load cases studied, the displacement computed from an equivalent single-degree-of-freedom system correspond fairly well to the displacement given by a refined two-dimensional beam model, reduced by substructuring. In contrast, the shear force differs significantly due to that higher order modes are neglected in the single-degree-of-freedom system.
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| 7. |
- Andersson, Linus, et al.
(författare)
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Reduced order modeling of soft-body impact on glass panels
- 2022
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Ingår i: Engineering Structures. - : Elsevier BV. - 0141-0296. ; 256
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Tidskriftsartikel (refereegranskat)abstract
- In the paper, strategies for reduced order modeling of glass panels subjected to soft-body impact are developed by means of dynamic substructuring. The aim is to obtain accurate and computationally efficient models for prediction of the pre-failure elastic response. More specifically, a reduction basis for the subsystem representing the glass panel is established using correction modes, being fixed-interface component modes that considers loading on the substructure boundary. The soft-body impactor is effectively modeled by a nonlinear single-degree-of-freedom system, calibrated by experimental data. Furthermore, a simplified and computationally efficient modeling approach is proposed for the contact interaction between the glass panel and the impact body. An experimental campaign was carried out to validate the developed models. In particular, the glass strain was measured on simply supported monolithic glass panels subjected to soft-body impact. Additional impact tests were performed to determine the dynamic characteristics of the impactor. Moreover, a detailed numerical reference model was developed to evaluate the discrepancy between the experimental tests and the results provided by the reduced order models. The developed models show good agreement with the experimental results. For the studied load cases, it is shown that an accurate prediction of the pre-failure glass strain can be obtained by systems including only a few generalized degrees-of-freedom.
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