| 1. |
- Gottsäter, Erik, et al.
(author)
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Comparison of Models for the Design of Portal Frame Bridges with Regard to Restraint Forces
- 2017
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In: Structures Congress 2017, Denver, United States, 6-8 April 2017. - Reston, VA : American Society of Civil Engineers. - 9780784480403 ; , s. 326-339
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Conference paper (peer-reviewed)abstract
- In the design of concrete bridges an important aspect is limiting crack widths, since large cracks can lead to e.g. corrosion and affect the bridge functionality. Restraint forces caused by thermal loads and shrinkage will likely constitute a large part of the total forces acting on the bridge in crack width design. In this paper, restraint stresses in portal frame bridges are calculated according to Eurocode with simple hand calculation models, 2D frame models and linear elastic 3D FE-models. The results are then compared and used in Eurocode crack width design methods. Large tensile restraint stresses were found in the transverse direction close to the frame corners, and the required reinforcement amount significantly exceeded the minimum reinforcement prescribed by codes. The results are however unrealistic since the thermal load distribution is simplified, and the crack width formula does not take the reduction of restraint stresses due to cracking into account. Future studies shall therefore determine a more realistic thermal load distribution and the effects of cracking, in order to create a more accurate linear elastic 3D FE design method.
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| 2. |
- Gottsäter, Erik, et al.
(author)
-
Crack widths in portal frame bridges subjected to restraint effects
- 2019
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In: 20th Congress of IABSE, New York City 2019: The Evolving Metropolis - Report. ; , s. 1101-1105, s. 1101-1105
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Conference paper (peer-reviewed)abstract
- Restraint stresses appear in structural parts which are prevented from adjusting their shape when subjected to e.g. shrinkage or thermal actions. If the restrained stresses are large, cracking might occur, which can affect the durability of the structure. In the case of restraint effects, the reinforcement required in a bridge to limit the crack widths can be difficult to determine, as the magnitude of the restraint stresses depend on the stiffness of the structure. If cracking occurs, the stiffness is reduced and thereby also the stresses. For this reason, in structural parts affected by restraint effects, it can be hard to estimate both the number of cracks that will appear and the resulting restraint stress that governs the crack widths. In this study, crack widths in a portal frame bridge subjected to thermal actions and shrinkage were investigated using non-linear FE analysis. A bond-slip relation was used for concrete-reinforcement interaction, as the resulting crack spacing was unknown. Corresponding analysis was performed using linear elastic material models and hand calculations of crack widths, for two different thermal load cases, and relations between the results from the different methods are presented. The result can lead to the development of a more accurate design model, which would lead to more efficient use of reinforcement.
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| 3. |
- Gottsäter, Erik, et al.
(author)
-
Measurements and simulation of temperature in a portal frame bridge
- 2018
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In: IABSE Symposium, Nantes 2018: Tomorrow's Megastructures. - 9783857481611 ; , s. S24-9-S24-16
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Conference paper (peer-reviewed)abstract
- Since thermal loads can cause cracking, they are important to consider in bridge design. In order to evaluate and develop thermal load cases based on real simulations, models for simulating temperatures can be used. In this paper, a model for thermal simulation is used to simulate temperature in a portal frame bridge outside Lund, Sweden. The results are compared with temperature measurements in 13 locations in the same bridge, which were made during a 12-month period. The results show that although many important material parameters were unknown, the model could recreate both daily and seasonal temperature variations, although it tended to render temperatures about 1°C lower than the measurements, at least during summer. The model can be used in future work in determining thermal load values for the specific bridge type, assuming the model uncertainty is considered by e.g. adding 1°C to calculated load values.
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| 4. |
- Gottsäter, Erik, et al.
(author)
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Simulation of thermal load distribution in portal frame bridges
- 2016
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In: IABSE Congress Stockholm, 2016: Challenges in Design and Construction of an Innovative and Sustainable Built Environment.
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Conference paper (peer-reviewed)abstract
- Uneven exposure to e.g. solar radiation can cause temperature differences between various structural parts of a bridge, which leads to tensile stresses if the parts cannot move freely. In this study, thermal simulations and stress calculations on a model of a portal frame bridge are performed with the aim of evaluating the temperature difference between the bridge parts. It is shown that the temperature difference between parts which is proposed by Eurocode 1 is overestimated, thus the resulting stress distribution being unrealistic. Using the design method proposed by Eurocode 1 is therefore likely to exaggerate the required reinforcement in crack width limit design, which in turn would lead to unnecessary costs and environmental impacts. Further studies are needed in order to determine proper thermal load values and temperature distributions.
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| 5. |
- Honfi, Daniel, et al.
(author)
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Decision support for maintenance and upgrading of existing bridges
- 2017
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In: IABSE Conference, Vancouver 2017. - : International Association for Bridge and Structural Engineering (IABSE). - 9783857481536 ; , s. 336-345, s. 336-345
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Conference paper (peer-reviewed)abstract
- Maintenance of transportation infrastructure assets can be relatively expensive, since it does not only include the direct cost of interventions, but also the indirect consequences of traffic disruptions. To make optimal decisions about maintenance actions, including rehabilitation and upgrading, reliable information about the performance of existing structures is needed. However, obtaining such information might require significant efforts and can be done in various ways. The purpose of an ongoing Swedish research project BIG BRO is to develop a framework for a decision support methodology that can be used for implementing maintenance strategies for bridges on a rational basis. The present paper provides a brief overview about the project as well as describes some of the ongoing work.
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