En 55 ar gammal spannbetongbro med fem spann med langden 121,5 m har provats till brott for att s... more En 55 ar gammal spannbetongbro med fem spann med langden 121,5 m har provats till brott for att studera och kalibrera metoder for tillstandsbedomning av befintliga broar. Projektet harbidragit till ...
In the design of concrete bridges an important aspect is limiting crack widths, since large crack... more 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.
The main objective of this background document is to bridge the gap between the most advanced str... more The main objective of this background document is to bridge the gap between the most advanced structural assessment techniques based on probabilistic methods and the daily practice of bridge evalua ...
In this study, it has been demonstrated and documented how higher load carrying capacity with res... more In this study, it has been demonstrated and documented how higher load carrying capacity with respect to combined shear and torsion can be shown for road bridges through non-linear finite element (FE) analyses. In this report, the evaluation of a prestressed box girder bridge, the Kallosund Bridge, is documented as a case study. The Kallosund bridge is a 45 years old, cast-in-situ concrete bridge with four spans, built with the free cantilevering method on the west coast of Sweden. A previously performed initial structural assessment, performed according to current regulations and common engineering practice, showed insufficient load carrying capacity, both with respect to combined shear and torsion in large parts of the bridge, and with respect to bending moment in the outer spans. Since the capability to simulate and demonstrate higher capacity with respect to bending, using FE analyses, have been showed in several cases previously, this study focused on combined shear and torsion...
Corrosion of steel reinforcement causes cracking and spalling of concrete cover which affects the... more Corrosion of steel reinforcement causes cracking and spalling of concrete cover which affects the bond; this is a crucial factor in deterioration of concrete structures. Earlier, anchorage tests have been carried out on specimens with naturally corroded reinforcements. In an ongoing study, the focus is given to the modelling of these specimens. The aim is to evaluate the structural behaviour of the tested naturally corroded specimens. The analyses are performed in the FE program Diana. The frictional bond and corrosion models developed by Lundgren and Zandi are implemented in interface elements to model the interaction between the concrete and reinforcements. The preliminary results of the analysis showed differences in the shear crack pattern in comparison with the experiments. In the analysis, a longer remaining anchorage length was obtained in comparison with the experiment which resulted in a wrong failure mode. The issue might be related to the influence of aggregate interlock ...
Den svenska anlaggningsbranschen har i ett flertal utredningar fatt skarp kritik pa grund av dali... more Den svenska anlaggningsbranschen har i ett flertal utredningar fatt skarp kritik pa grund av dalig produktivitet. Forskning visar pa samma tendenser i ovriga Europa och USA. Vissa matningar tyder pa att byggandet i den svenska anlaggningsbranschen har en kostnadsokning som ar dubbelt sa hog jamfort med ovriga branscher under de senaste 20 aren. Lag produktivitet och lag innovationsformaga i byggbranschen leder till hogre kostnader som inte garanterat ger en hogre kvalitet. Trenden behover vandas sa att avkastningen pa investeringar i var infrastruktur okar! Det forsta steget ar att integrera konstruktions- och produktionsprocesserna, vilket ger kortare ledtider for bade planering och uppforande av byggnadsverk. Onodigt langa byggtider orsakar storningar for andra aktorer i samhallet. I ett pagaende doktorandprojekt, som ar ett samarbete mellan Trafikverket, WSP och Chalmers, soks mojligheten till att oka produktiviteten inom den svenska anlaggningsbranschen. Huvudsparet ar att utvec...
IABSE Congress, New York, New York 2019: The Evolving Metropolis, 2019
Restraint stresses appear in structural parts which are prevented from adjusting their shape when... more 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 wa...
IABSE Symposium, Vancouver 2017: Engineering the Future, 2017
The design of buildings and load carrying structures in early stages is a challenging task for a ... more The design of buildings and load carrying structures in early stages is a challenging task for a number of reasons; scant information generally exists and several different requirements involving building structures should be managed, including technical, environmental and financial requirements. However, this phase of the design process is important and will fundamentally influence the following construction phase, as well as the entire life of building structures. It is particularly important that the construction phase is properly considered already in the design phase and that the production method selected is suitable for the design of building structures. The purpose of this research has been to improve the design process in the conceptual phase. The findings will highlight the benefits of design for production in bridge engineering. The aim has been to identify examples of practices and work methodologies that are of good caliber in the Swedish bridge construction sector. Ear...
This report presents methodology, results and conclusions from the PhD-project “Evaluation, model... more This report presents methodology, results and conclusions from the PhD-project “Evaluation, modeling and handling of restraint stresses in concrete bridges”, which can be relevant for bridge designers. The project investigated thermal actions in portal frame bridges, and the widths of cracks resulting from restraint effects. The main results and conclusions are given in the summary in Swedish, while the following parts in English presents both results and conclusions, as well as the methodology.The report is developed as a guide for practicing bridge designers on how the load case describing temperature differences between structural parts can be included in design. It also highlights the difficulties and need for further research on determining what the resulting crack widths are and how to design crack distribution reinforcement when cracking is caused by restraint effects.An extensive summary in Swedish is also part of the report.
IABSE Symposium, Vancouver 2017: Engineering the Future, 2017
For reinforced concrete (RC) slabs without shear reinforcement, shear and punching can be the gov... more For reinforced concrete (RC) slabs without shear reinforcement, shear and punching can be the governing failure mode at ultimate limit state if subjected to large concentrated loads. Punching of RC slabs without shear reinforcement has been a challenging problem in assessment based on current standards. To examine a previously developed enhanced analysis approach, this study was conducted by applying continuum FE analyses to a 55-year old RC bridge deck slab subjected to concentrated loads near the main girder in a field failure test. The influence of parameters such as boundary conditions, location of concentrated loads and shear force distribution were investigated.
IABSE Conference, Rotterdam 2013: Assessment, Upgrading and Refurbishment of Infrastructures, 2013
Corrosion of reinforcement is a significant cause of deterioration in existing structures. While ... more Corrosion of reinforcement is a significant cause of deterioration in existing structures. While this topic has been extensively studied using artificially corroded test specimens, little is known about the actual response of naturally corroded structures. Overall, the literature suggests that drastic reduction of the corrosion time, i.e. from years to days, in accelerated corrosion process, might markedly influence the bond and the anchorage capacity of a reinforced concrete member.Consequently, the anchorage capacity of specimens with naturally corroded reinforcement was investigated. Since a large scatter was observed in the tests of the first series, see [1, 2], fourteen more specimens were tested in a second round using samples from the other side of the same bridge. The specimens were carefully documented regarding crack patterns, crack widths, and spalled regions before testing. In all cases, diagonal shear cracks preceded a splitting-induced pull- out failure; i.e. anchorage...
The growing need for reliable methods to evaluate the load-carrying capacity and remaining servic... more The growing need for reliable methods to evaluate the load-carrying capacity and remaining service life of deteriorated concrete structures has exposed the request for improved understanding of damage effects upon structural integrity. The presented research deals with the two most common causes of deterioration due to environmental impacts which are corrosion of reinforcement and freezing. Corrosion process leads to reduction
The bond properties of naturally corroded reinforced concrete members were experimentally investi... more The bond properties of naturally corroded reinforced concrete members were experimentally investigated. Thirteen specimens were taken from the northern edge beam of Stallbacka Bridge, a girder bridge in Sweden. The specimens exhibited different levels of corrosion-induced damage, including concrete cracking and cover spalling. The damage was carefully documented and the specimens were tested in suspended four-point bending tests. Their general behaviour was monitored through measurements of applied loads and vertical deflections. At the same time, the local anchorage behaviour was recorded at the end regions. The test results showed around 5% lower anchorage capacity for damaged specimens compared with the reference ones. The residual bond strength was studied with respect to the observed damage. These tests, and artificial corrosion results from the literature, indicate that the bond strength decreased with increasing maximum splitting crack widths. However, the bond capacity was h...
En 55 ar gammal spannbetongbro med fem spann med langden 121,5 m har provats till brott for att s... more En 55 ar gammal spannbetongbro med fem spann med langden 121,5 m har provats till brott for att studera och kalibrera metoder for tillstandsbedomning av befintliga broar. Projektet harbidragit till ...
In the design of concrete bridges an important aspect is limiting crack widths, since large crack... more 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.
The main objective of this background document is to bridge the gap between the most advanced str... more The main objective of this background document is to bridge the gap between the most advanced structural assessment techniques based on probabilistic methods and the daily practice of bridge evalua ...
In this study, it has been demonstrated and documented how higher load carrying capacity with res... more In this study, it has been demonstrated and documented how higher load carrying capacity with respect to combined shear and torsion can be shown for road bridges through non-linear finite element (FE) analyses. In this report, the evaluation of a prestressed box girder bridge, the Kallosund Bridge, is documented as a case study. The Kallosund bridge is a 45 years old, cast-in-situ concrete bridge with four spans, built with the free cantilevering method on the west coast of Sweden. A previously performed initial structural assessment, performed according to current regulations and common engineering practice, showed insufficient load carrying capacity, both with respect to combined shear and torsion in large parts of the bridge, and with respect to bending moment in the outer spans. Since the capability to simulate and demonstrate higher capacity with respect to bending, using FE analyses, have been showed in several cases previously, this study focused on combined shear and torsion...
Corrosion of steel reinforcement causes cracking and spalling of concrete cover which affects the... more Corrosion of steel reinforcement causes cracking and spalling of concrete cover which affects the bond; this is a crucial factor in deterioration of concrete structures. Earlier, anchorage tests have been carried out on specimens with naturally corroded reinforcements. In an ongoing study, the focus is given to the modelling of these specimens. The aim is to evaluate the structural behaviour of the tested naturally corroded specimens. The analyses are performed in the FE program Diana. The frictional bond and corrosion models developed by Lundgren and Zandi are implemented in interface elements to model the interaction between the concrete and reinforcements. The preliminary results of the analysis showed differences in the shear crack pattern in comparison with the experiments. In the analysis, a longer remaining anchorage length was obtained in comparison with the experiment which resulted in a wrong failure mode. The issue might be related to the influence of aggregate interlock ...
Den svenska anlaggningsbranschen har i ett flertal utredningar fatt skarp kritik pa grund av dali... more Den svenska anlaggningsbranschen har i ett flertal utredningar fatt skarp kritik pa grund av dalig produktivitet. Forskning visar pa samma tendenser i ovriga Europa och USA. Vissa matningar tyder pa att byggandet i den svenska anlaggningsbranschen har en kostnadsokning som ar dubbelt sa hog jamfort med ovriga branscher under de senaste 20 aren. Lag produktivitet och lag innovationsformaga i byggbranschen leder till hogre kostnader som inte garanterat ger en hogre kvalitet. Trenden behover vandas sa att avkastningen pa investeringar i var infrastruktur okar! Det forsta steget ar att integrera konstruktions- och produktionsprocesserna, vilket ger kortare ledtider for bade planering och uppforande av byggnadsverk. Onodigt langa byggtider orsakar storningar for andra aktorer i samhallet. I ett pagaende doktorandprojekt, som ar ett samarbete mellan Trafikverket, WSP och Chalmers, soks mojligheten till att oka produktiviteten inom den svenska anlaggningsbranschen. Huvudsparet ar att utvec...
IABSE Congress, New York, New York 2019: The Evolving Metropolis, 2019
Restraint stresses appear in structural parts which are prevented from adjusting their shape when... more 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 wa...
IABSE Symposium, Vancouver 2017: Engineering the Future, 2017
The design of buildings and load carrying structures in early stages is a challenging task for a ... more The design of buildings and load carrying structures in early stages is a challenging task for a number of reasons; scant information generally exists and several different requirements involving building structures should be managed, including technical, environmental and financial requirements. However, this phase of the design process is important and will fundamentally influence the following construction phase, as well as the entire life of building structures. It is particularly important that the construction phase is properly considered already in the design phase and that the production method selected is suitable for the design of building structures. The purpose of this research has been to improve the design process in the conceptual phase. The findings will highlight the benefits of design for production in bridge engineering. The aim has been to identify examples of practices and work methodologies that are of good caliber in the Swedish bridge construction sector. Ear...
This report presents methodology, results and conclusions from the PhD-project “Evaluation, model... more This report presents methodology, results and conclusions from the PhD-project “Evaluation, modeling and handling of restraint stresses in concrete bridges”, which can be relevant for bridge designers. The project investigated thermal actions in portal frame bridges, and the widths of cracks resulting from restraint effects. The main results and conclusions are given in the summary in Swedish, while the following parts in English presents both results and conclusions, as well as the methodology.The report is developed as a guide for practicing bridge designers on how the load case describing temperature differences between structural parts can be included in design. It also highlights the difficulties and need for further research on determining what the resulting crack widths are and how to design crack distribution reinforcement when cracking is caused by restraint effects.An extensive summary in Swedish is also part of the report.
IABSE Symposium, Vancouver 2017: Engineering the Future, 2017
For reinforced concrete (RC) slabs without shear reinforcement, shear and punching can be the gov... more For reinforced concrete (RC) slabs without shear reinforcement, shear and punching can be the governing failure mode at ultimate limit state if subjected to large concentrated loads. Punching of RC slabs without shear reinforcement has been a challenging problem in assessment based on current standards. To examine a previously developed enhanced analysis approach, this study was conducted by applying continuum FE analyses to a 55-year old RC bridge deck slab subjected to concentrated loads near the main girder in a field failure test. The influence of parameters such as boundary conditions, location of concentrated loads and shear force distribution were investigated.
IABSE Conference, Rotterdam 2013: Assessment, Upgrading and Refurbishment of Infrastructures, 2013
Corrosion of reinforcement is a significant cause of deterioration in existing structures. While ... more Corrosion of reinforcement is a significant cause of deterioration in existing structures. While this topic has been extensively studied using artificially corroded test specimens, little is known about the actual response of naturally corroded structures. Overall, the literature suggests that drastic reduction of the corrosion time, i.e. from years to days, in accelerated corrosion process, might markedly influence the bond and the anchorage capacity of a reinforced concrete member.Consequently, the anchorage capacity of specimens with naturally corroded reinforcement was investigated. Since a large scatter was observed in the tests of the first series, see [1, 2], fourteen more specimens were tested in a second round using samples from the other side of the same bridge. The specimens were carefully documented regarding crack patterns, crack widths, and spalled regions before testing. In all cases, diagonal shear cracks preceded a splitting-induced pull- out failure; i.e. anchorage...
The growing need for reliable methods to evaluate the load-carrying capacity and remaining servic... more The growing need for reliable methods to evaluate the load-carrying capacity and remaining service life of deteriorated concrete structures has exposed the request for improved understanding of damage effects upon structural integrity. The presented research deals with the two most common causes of deterioration due to environmental impacts which are corrosion of reinforcement and freezing. Corrosion process leads to reduction
The bond properties of naturally corroded reinforced concrete members were experimentally investi... more The bond properties of naturally corroded reinforced concrete members were experimentally investigated. Thirteen specimens were taken from the northern edge beam of Stallbacka Bridge, a girder bridge in Sweden. The specimens exhibited different levels of corrosion-induced damage, including concrete cracking and cover spalling. The damage was carefully documented and the specimens were tested in suspended four-point bending tests. Their general behaviour was monitored through measurements of applied loads and vertical deflections. At the same time, the local anchorage behaviour was recorded at the end regions. The test results showed around 5% lower anchorage capacity for damaged specimens compared with the reference ones. The residual bond strength was studied with respect to the observed damage. These tests, and artificial corrosion results from the literature, indicate that the bond strength decreased with increasing maximum splitting crack widths. However, the bond capacity was h...
Uploads