| 1. |
- Abrahamsen, Rune, et al.
(författare)
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Dynamic Response of Tall Timber Buildings Under Service Load : The DynaTTB Research Program
- 2020
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Ingår i: EURODYN 2020, XI international conferece on structural dynamics. - : National Technical University of Athens. - 9786188507210 ; , s. 4900-4910
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Konferensbidrag (refereegranskat)abstract
- Wind-induced dynamic excitation is becoming a governing design action determin-ing size and shape of modern Tall Timber Buildings (TTBs). The wind actions generate dynamic loading, causing discomfort or annoyance for occupants due to the perceived horizontal sway – i.e. vibration serviceability failure. Although some TTBs have been instrumented and meas-ured to estimate their key dynamic properties (natural frequencies and damping), no systematic evaluation of dynamic performance pertinent to wind loading has been performed for the new and evolving construction technology used in TTBs. The DynaTTB project, funded by the Forest Value research program, mixes on site measurements on existing buildings excited by heavy shakers, for identification of the structural system, with laboratory identification of building elements mechanical features coupled with numerical modelling of timber structures. The goal is to identify and quantify the causes of vibration energy dissipation in modern TTBs and pro-vide key elements to FE modelers.The first building, from a list of 8, was modelled and tested at full scale in December 2019. Some results are presented in this paper. Four other buildings will be modelled and tested in spring 2020.
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| 2. |
- Abrahamsen, Rune, et al.
(författare)
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Dynamic response of tall timber buildings under service load : results from the dynattb research program
- 2023
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Ingår i: World Conference on Timber Engineering 2023 (WCTE 2023). - : Curran Associates, Inc.. - 9781713873297 ; , s. 2907-2914
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Konferensbidrag (refereegranskat)abstract
- Wind-induced dynamic excitation is a governing design action determining size and shape of modern Tall Timber Buildings (TTBs). The wind actions generate dynamic loading, causing discomfort or annoyance for occupants due to the perceived horizontal sway, i.e. vibration serviceability problem. Although some TTBs have been instrumented and measured to estimate their key dynamic properties (eigenfrequencies, mode shapes and damping), no systematic evaluation of dynamic performance pertinent to wind loading had been performed for the new and evolving construction technologies used in TTBs. The DynaTTB project, funded by the ForestValue research program, mixed on site measurements on existing buildings excited by mass inertia shakers (forced vibration) and/or the wind loads (ambient vibration), for identification of the structural system, with laboratory identification of building elements mechanical features, coupled with numerical modelling of timber structures. The goal is to identify and quantify the causes of vibration energy dissipation in modern TTBs and provide key elements to finite element models. This paper presents an overview of the results of the project and the proposed Guidelines for design of TTBs in relation to their dynamic properties.
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| 3. |
- Landel, Pierre, 1981-
(författare)
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Wind-induced vibrations in tall timber buildings : Design standards, experimental and numerical modal analyses
- 2022
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Climate change and densification of cities are two major global challenges. Inthe building and construction industry, there are great expectations that tall timberbuildings will constitute one of the most sustainable solutions. First, verticalurban growth is energy and resource-efficient. Second, forest-based productsstore carbon and have one of the highest mechanical strength to density ratios.If the structural substitution of concrete and steel with wood in high-rise buildingsawakens fears of fire safety issues, engineers and researchers are particularlyworried about the dynamic response of the trendy tall timber buildings.Indeed, due to the low density of wood, they are lighter, and for the same height,they might be more sensitive to wind-induced vibrations than traditional buildings.To satisfy people’s comfort on the top floors, the serviceability design oftall timber buildings must consider wind-induced vibrations carefully. Architectsand structural engineers need accurate and verified calculation methods,useful numerical models and good knowledge of the dynamical properties oftall timber buildings.Firstly, the research work presented hereby attempts to increase the understandingof the dynamical phenomena of wind-induced vibration in tall buildings andevaluate the accuracy of the semi-empirical models available to estimate alongwindaccelerations in buildings. Secondly, it aims at, experimentally and numerically,studying the impact of structural parameters – masses, stiffnesses anddamping – on the dynamics of timber structures. Finally, it suggests how talltimber buildings can be modeled to correctly predict modal properties and windinducedresponses.This research thesis confirms the concerns that timber buildings above 15-20stories are more sensitive to wind excitation than traditional buildings with concreteand steel structures, and solutions are proposed to mitigate this vibrationissue. Regarding the comparison of models from different standards to estimatewind-induced accelerations, the spread of the results is found to be very large.From vibration tests on a large glulam truss, the connection stiffnesses are foundto be valuable for predicting modal properties, and numerical reductions withsimple spring models yield fair results. Concerning the structural models of conceptualand real tall timber buildings, numerical case studies emphasize the importanceof accurately distributed masses and stiffnesses of structural elements,connections and non-structural building parts, and the need for accurate dampingvalues.
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| 4. |
- Nåvik, Petter, et al.
(författare)
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Variation in predicting pantograph-catenary interaction contact forces, numerical simulations and field measurements
- 2017
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Ingår i: Vehicle System Dynamics. - : Taylor & Francis. - 0042-3114 .- 1744-5159. ; 55:9, s. 1265-1282
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Tidskriftsartikel (refereegranskat)abstract
- The contact force between the pantograph and the contact wire ensures energy transfer between the two. Too small of a force leads to arching and unstable energy transfer, while too large of a force leads to unnecessary wear on both parts. Thus, obtaining the correct contact force is important for both field measurements and estimates using numerical analysis. The field contact force time series is derived from measurements performed by a self-propelled diagnostic vehicle containing overhead line recording equipment. The measurements are not sampled at the actual contact surface of the interaction but by force transducers beneath the collector strips. Methods exist for obtaining more realistic measurements by adding inertia and aerodynamic effects to the measurements. The variation in predicting the pantograph-catenary interaction contact force is studied in this paper by evaluating the effect of the force sampling location and the effects of signal processing such as filtering. A numerical model validated by field measurements is used to study these effects. First, this paper shows that the numerical model can reproduce a train passage with high accuracy. Second, this study introduces three different options for contact force predictions from numerical simulations. Third, this paper demonstrates that the standard deviation and the maximum and minimum values of the contact force are sensitive to a low-pass filter. For a specific case, an 80Hz cut-off frequency is compared to a 20Hz cut-off frequency, as required by EN 50317:2012; the results show an 11% increase in standard deviation, a 36% increase in the maximum value and a 19% decrease in the minimum value.
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