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| 2. |
- 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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| 3. |
- 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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| 6. |
- Hu, Min, 1979-, et al.
(författare)
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Grading of sawn timber using the vibration technique : locating imperfections based on flexural mode shapes
- 2011
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Ingår i: 17th international nondestructive testing and evaluation of wood symposium. - Sopron, Hungary : University of West Hungary. - 9789639883819 ; , s. 269-276
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Konferensbidrag (refereegranskat)abstract
- The present study aims at investigating the potential of using mode shape or mode shape curvature (MSC) for detecting defects in wooden beams. It includes modal analysis, Finite Element (FE) modeling and visual scanning. An FE model was created to investigate the effect of defects of different size and location on the mode shape/MSC. The mode shape/MSC showed a good potential to be used for finding defects. An experimental study on 17 boards of Norway spruce, dimensions of 50×150×3900 mm, was conducted using experimental modal analysis. The findings reveal that: (1) the mode shape/MSC studied in the FE-model could be used to locate defects, (2) the method is very sensitive to measurement noise and it requires an accurately measured mode shape, (3) an error analysis shows that it is not possible to achieve the accuracy needed using accelerometers.
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| 7. |
- Mårtensson, Fredrika, et al.
(författare)
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The role of greenery for physical activity play at school grounds
- 2014
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Ingår i: Urban Forestry & Urban Greening. - : Elsevier BV. - 1618-8667 .- 1610-8167. ; 13:1, s. 103-113
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Tidskriftsartikel (refereegranskat)abstract
- Greenery is assumed to promote physical activity at school grounds by facilitating open and flexible play situations that engage many children. The role of greenery for school ground activity was investigated at two schools, one of which contained a substantial amount of greenery and the other one little greenery. All in all 197 children from 4th (10-11 years) and 6th grade (12-13 years), were involved in a one week field study, documenting self-reported school ground use, their favourite places and favourite activities and counting their steps by pedometer. The most common school ground activities were related to the use of balls as part of different sports, games and other playful activity. The more extensive green areas belonged to children's favourite places, but were little used, whereas settings with a mix of green and built elements in proximity to buildings were well-used favourites. Physical activity in steps was similar at the two schools, but on average girls got less of the activity they need during recess. Greenery was found important by contributing to settings attractive to visit for girls as well as boys and for younger as well as older children, if located in ways that also supported peer interaction and various games. (C) 2013 Elsevier G'mbH. All rights reserved.
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| 8. |
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NORLIT 2009, Codex and Code: Aestethcis, Language and Politics in an Age of Digital Media : Stockholm, August 6-9, 2009
- 2010
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Proceedings (redaktörskap) (refereegranskat)abstract
- The aim of the conference was to develop the study of Comparative Literature through Nordic collaboration both in its own discipline and in Modern Language and Cultural studies. As the title for the conference suggests, the principal question for the conference was the challenge that the study of literature encounters in an age of digitalization and globalization. It was our aim to encourage discussion of how literary studies respond to the ongoing changes in media and technology, politics and economy. Many have argued that the Humanities currently are in a state of crisis. We believe that the discipline seldom has found itself in such an interesting and fruitful historical moment. Several of these questions have surfaced duringearlier media system changes, in particular during Romanticism and Modernism, which provided the conference with an historical frame. The conference Codex and Code also addressed questions of authenticity and originality, identity and gender, literary genres and reading practices, media and materiality, culture and popular culture, language and history, world literature, work aesthetics, translations, and canon formation.
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| 9. |
- Tornberg, Åsa B.B., et al.
(författare)
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Reduced Neuromuscular Performance in Amenorrheic Elite Endurance Athletes
- 2017
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Ingår i: Medicine & Science in Sports & Exercise. - : Lippincott Williams & Wilkins. - 0195-9131 .- 1530-0315. ; 49:12, s. 2478-2485
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Tidskriftsartikel (refereegranskat)abstract
- Introduction Secondary functional hypothalamic amenorrhea (SFHA) is common among female athletes, especially in weight-sensitive sports. The aim of this study was to investigate the link between SFHA and neuromuscular performance in elite endurance athletes. Methods Sixteen eumenorrheic (EUM) and 14 SFHA athletes from national teams and competitive clubs participated. Methods included gynecological examination, body composition (dual-energy x-ray absorptiometry), resting metabolic rate and work efficiency, exercise capacity, knee muscular strength (KMS) and knee muscular endurance (KME), reaction time (RT), blood sampling performed on the third to fifth days of the menstrual cycle, and 7-d assessment of energy availability. Results SFHA athletes had lower estrogen (0.12 0.03 vs 0.17 +/- 0.09 nmolL(-1), P < 0.05), triiodothyronine (T-3) (1.4 +/- 0.2 vs 1.7 +/- 0.3 nmolL(-1), P < 0.01), and blood glucose (3.8 +/- 0.3 vs 4.4 +/- 0.3 mmolL(-1), P < 0.001) but higher cortisol levels (564 +/- 111 vs 400 +/- 140 nmolL(-1), P < 0.05) compared with EUM athletes. SFHA had a lower body weight (55.0 +/- 5.8 vs 60.6 +/- 7.1 kg, P < 0.05), but no difference in exercise capacity between groups was found (56.4 +/- 5.8 vs 54.0 +/- 6.3 mL O(2)min(-1)kg(-1)). RT was 7% longer, and KMS and KME were 11% and 20% lower compared with EUM athletes. RT was negatively associated with glucose (r = -0.40, P < 0.05), T-3 (r = -0.37, P < 0.05), and estrogen (r = -0.43, P < 0.05), but positively associated with cortisol (r = 0.38, P < 0.05). KMS and KME correlated with fat-free mass in the tested leg (FFMleg; r = 0.52, P < 0.001; r = 0.58, P < 0.001) but were negatively associated with cortisol (r = -0.42, P < 0.05; r = -0.59, P < 0.001). FFMleg explained the differences in KMS, while reproductive function and FFMleg independently explained the variability in KME. Conclusions We found lower neuromuscular performance among SFHA compared with EUM athletes linked to a lower FFMleg, glucose, estrogen, T-3, and elevated cortisol levels.
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| 10. |
- Andersen, Michael Styrk, et al.
(författare)
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Aerodynamic stability of long span suspension bridges with low torsional natural frequencies
- 2016
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Ingår i: Engineering structures. - : Elsevier. - 0141-0296 .- 1873-7323. ; 120, s. 82-91
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Tidskriftsartikel (refereegranskat)abstract
- Classical flutter of suspended bridge decks can be avoided if the torsional frequencies are lower than the vertical. Wind tunnel tests of single boxes and twin box section models with torsional natural frequencies above and below the vertical frequency has been conducted. Flutter was avoided in all tests where the torsional frequency was lower than the vertical. But too low torsional stiffness caused large static displacements of the girder at medium–high wind speeds and steady state oscillations driven by a combination of torsional divergence and stalling behavior at the critical wind seed. In order to design aerodynamically stable suspension bridges with low torsional natural frequencies it is suggested to increase the mass moment of inertia and provide adequate torsional stiffness by the main cables spacing.
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