| 1. |
- Agredo Chavez, Angelica Maria, et al.
(författare)
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Cracking and Fatigue of Heavy Loaded Prestressed Concrete Bridge in Sweden
- 2022
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Ingår i: IABSE Symposium Prague 2022: Challenges for Existing and Oncoming Structures - Report, International Association for Bridge and Structural Engineering. - Zürich : International Association for Bridge and Structural Engineering. ; , s. 792-799
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Konferensbidrag (refereegranskat)abstract
- A prestressed concrete bridge was built in 1963 with BBRV cables. It has three spans and a total length of 134.8 m. Due to mining activities the bridge was loaded with trucks with a total weight of 90 ton during 2012-2014 and from 2019. Crack development has been monitored manually and from 2020 with strain gauges and LVDTs.Cracks normally vary between 0.1 to 0.3 mm in width and grow in length with time. In November 2020 some of the strain gauges on the concrete showed alarming growth and the bridge was closed for traffic. Additional strain gauges were installed on vertical reinforcement bars and an assessment was carried out of the fatigue capacity of the bridge. It was found that the new strain gauges did not indicate any growth in strain and that the fatigue capacity was sufficient. The bridge could be opened again for traffic after being closed for five weeks. Monitoring drift in the strain gauges and fatigue are discussed.
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| 2. |
- Andersson-Sköld, Yvonne, 1957-, et al.
(författare)
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Development of the SUNRA Tool to Improve Regional and Local Sustainability of the Transportation Sector
- 2022
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Ingår i: Sustainability. - : MDPI AG. - 2071-1050. ; 14:18, s. 11275-
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Tidskriftsartikel (refereegranskat)abstract
- To fulfil the global sustainable development goals (SDGs), achieving sustainable development is becoming urgent, not least in the transportation sector. In response to this, the sustainability framework Sustainability National Road Administrations (SUNRA) was developed to contribute to improving the sustainability performance of national road administrations across Europe. In the present study, the framework has been tested, applied and further developed to be applicable for target setting and follow-up at the project level at both the Swedish Transport Administration (STA) and at municipal levels. The aim was a framework relevant for investment, re-investments, maintenance and operation projects and also to make it more user applicable. The study also investigated how the framework can contribute to sustainability, identified drivers and barriers for applying the framework and examined whether the framework can be applied and adapted to projects of different complexities. The adaptations and developments were done in collaboration between researchers and practitioners. The results show that the framework could easily be used and adapted for investment, re-investment, maintenance and operation projects in the planning stage, as well as for small municipal establishments, construction or reconstruction of residential areas and frequent maintenance. The framework contributes to increased awareness on sustainability, and it provides a common structure and transparency on how infrastructure project goals/targets are set and fulfilled. The framework can also be applied to follow the fulfilment of the goals/targets and thereby adapt the project to better fulfil the goals. Identified barriers include the lack of obligations and lack of experience in using sustainability frameworks.
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| 3. |
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| 4. |
- Persson, Gustav, et al.
(författare)
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Splenic contraction and cardiovascular responses are augmented during apnea compared to rebreathing in humans
- 2023
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Ingår i: Frontiers in Physiology. - : Frontiers Media SA. - 1664-042X. ; 14
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Tidskriftsartikel (refereegranskat)abstract
- The spleen contracts during apnea, releasing stored erythrocytes, thereby increasing systemic hemoglobin concentration (Hb). We compared apnea and rebreathing periods, of equal sub-maximal duration (mean 137 s; SD 30), in eighteen subjects to evaluate whether respiratory arrest or hypoxic and hypercapnic chemoreceptor stimulation is the primary elicitor of splenic contraction and cardiovascular responses during apnea. Spleen volume, Hb, cardiovascular variables, arterial (SaO2), cerebral (ScO2), and deltoid muscle oxygen saturations (SmO2) were recorded during the trials and end-tidal partial pressure of oxygen (PETO2) and carbon dioxide (PETCO2) were measured before and after maneuvers. The spleen volume was smaller after apnea, 213 (89) mL, than after rebreathing, 239 (95) mL, corresponding to relative reductions from control by 20.8 (17.8) % and 11.6 (8.0) %, respectively. The Hb increased 2.4 (2.0) % during apnea, while there was no significant change with rebreathing. The cardiovascular responses, including bradycardia, decrease in cardiac output, and increase in total peripheral resistance, were augmented during apnea compared to during rebreathing. The PETO2 was higher, and the PETCO2 was lower, after apnea compared to after rebreathing. The ScO2 was maintained during maneuvers. The SaO2 decreased 3.8 (3.1) % during apnea, and even more, 5.4 (4.4) %, during rebreathing, while the SmO2 decreased less during rebreathing, 2.2 (2.8) %, than during apnea, 8.3 (6.2) %. We conclude that respiratory arrest per se is an important stimulus for splenic contraction and Hb increase during apnea, as well as an important initiating factor for the apnea-associated cardiovascular responses and their oxygen-conserving effects.
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| 5. |
- Andersson, Angelica
(författare)
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Combined speckle interferometry and speckle correlation for non-destructive testing
- 2000
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- When a sample is studied during loading in a tensile test machine, the sample is often exposed to rigid body motions during loading at the same time as it deforms due to tension. Therefore, the small deformation field is hard, or impossible, to measure when it is overlaid by a large motion. The large rigid body motions can be measured with methods like speckle correlation (also called digital speckle photography, DSP), but the results might be of too poor accuracy to resolve the deformation field. Interferometric methods on the other hand might measure the deformation field but the rigid body motion makes the fringes disappear. In this thesis a method is presented that makes it possible to master such measuring situations, by a combination of speckle correlation and speckle interferometry (also called TV holography, ESPI or DSPI). Both theory and experiments are presented. It is shown that speckle correlation can determine the speckle motion in the recording in order to determine the small deformation field in the interferometric algorithm. Speckle correlation can also be used to determine the amount of shear in shearography allowing a quantitative determination of the spatial derivative of the deformation field.
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| 6. |
- Andersson, Angelica, et al.
(författare)
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Digital speckle-pattern interferometry: fringe retrieval for large in-plane deformations with digital speckle photography
- 1999
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Ingår i: Applied Optics. - : Optical Society of America. - 1559-128X .- 2155-3165. ; 38:25, s. 5408-5412
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Tidskriftsartikel (refereegranskat)abstract
- The compensation of large in-plane motions in digital speckle-pattern interferometry (DSPI) with the use of digital speckle photography (DSP) is demonstrated. Ordinary recordings of DSPI are recombined and analyzed with DSP. The DSP result is used to compensate for the bulk speckle motion prior to calculation of the phase map. This results in a high fringe contrast even for deformations of several speckle diameters. In addition, for the case of an in-plane deformation, it is shown that the absolute phase change in each pixel may be unwrapped by use of the DSP result as an initial guess. The principles of this method and experiments showing the in-plane rotation of a plate and the encounter of two rounded plates are presented
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| 7. |
- Andersson, Angelica, et al.
(författare)
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Long-distance mode choice estimation on joint travel survey and mobile phone network data
- 2024
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Ingår i: Sammanställning av referat från Transportforum 2024. - Linköping : Statens väg- och transportforskningsinstitut. ; , s. 91-92
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Both survey data and mobile phone network data are associated with benefits and limitations. Mobile phone network data is limited in its lack of ground truth for the bus and car split, in the lack of socio-economic information about the traveller, as well as in the lack of information about trip purpose. Survey data on the other hand nowadays often has too few observations to obtain significance in important parameters, and it is unlikely that they capture a representative sample of the population. In this paper we investigate to what extent combining the two data sources for mode choice demand model estimation can mitigate the challenges present when only using a single data source, as well as to what extent the estimation can be improved by adding variables unique to the survey data. We also provide recommendations for data collection and combination for future mode choice demand models and analyse policy implications of the estimated results. We show that in our case the business cost parameter becomes insignificant when basing the estimation on survey data only. The business cost parameter is important to compute values of travel times which are relevant for social cost benefit analyses. A benefit of combining the two data sources is that we can both identify latent class variables which capture the correct business group in the latent class structure of the mobile phone network data, and simultaneously obtain better estimates of those variables based on observations from the survey data. Most of the elasticity results in this paper are on par with previous studies; however our results suggest higher cross-elasticities in response to train travel time than what has previously been observed, which could have implications for the social valuation of investments in high speed rail. In this paper we have shown that the proposed method of data combination is indeed valid, and that by combining the two data sources we can mitigate the limitations of each separate data source and thus maintain good quality mode choice demand forecasting models, even in the face of declining survey response rates.
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| 8. |
- Andersson, Angelica, et al.
(författare)
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Long-distance mode choice model estimation using mobile phone network data
- 2022
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Ingår i: Journal of Choice Modelling. - : Elsevier. - 1755-5345. ; 42
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we develop two methods for the use of mobile phone data to support the estimation of long-distance mode choice models. Both methods are based on logit formulations in which we define likelihood functions and use maximum likelihood estimation. Mobile phone data consists of information about a sequence of antennae that have detected each phone, so the mode choice is not actually observed. In the first trip-based method, the mode of each trip is inferred by a separate procedure, and the estimation process is then straightforward. However, since it is not always possible to determine the mode choice with certainty (although it is possible in the majority of cases), this method might give biased results. In our second antenna-based method we therefore base the likelihood function on the sequences of antennae that have detected the phones. The estimation aims at finding a parameter vector in the mode choice model that would explain the observed sequences best. The main challenge with the antenna-based method is the need for detailed resolution of the available data. In this paper we show the derivation of the two methods, that they coincide in case of certainty about the chosen mode and discuss the validity of assumptions and their advantages and disadvantages. Furthermore, we apply the first trip-based method to empirical data and compare the results of two different ways of implementing it.
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| 9. |
- Andersson, Angelica, et al.
(författare)
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Long-distance mode choice model estimation using mobile phone network data
- 2022
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Ingår i: Journal of Choice Modelling. - : Elsevier. - 1755-5345. ; 42
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper we develop two methods for the use of mobile phone data to support the estimation of long-distance mode choice models. Both methods are based on logit formulations in which we define likelihood functions and use maximum likelihood estimation. Mobile phone data consists of information about a sequence of antennae that have detected each phone, so the mode choice is not actually observed. In the first trip-based method, the mode of each trip is inferred by a separate procedure, and the estimation process is then straightforward. However, since it is not always possible to determine the mode choice with certainty (although it is possible in the majority of cases), this method might give biased results. In our second antenna-based method we therefore base the likelihood function on the sequences of antennae that have detected the phones. The estimation aims at finding a parameter vector in the mode choice model that would explain the observed sequences best. The main challenge with the antenna-based method is the need for detailed resolution of the available data. In this paper we show the derivation of the two methods, that they coincide in case of certainty about the chosen mode and discuss the validity of assumptions and their advantages and disadvantages. Furthermore, we apply the first trip-based method to empirical data and compare the results of two different ways of implementing it.
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| 10. |
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