| 1. |
- Blomfors, Mattias, 1990, et al.
(författare)
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Development of engineering assessment method for anchorage in reinforced concrete
- 2016
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Ingår i: Nordic Concrete Research. ; 2/2016:55, s. 63-78
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Konferensbidrag (refereegranskat)abstract
- There is an increasing need for reliable methods to assess load-carrying capacity and remaining service life of existing infrastructure. Several previous research projects have resulted in a verified, simple 1D model for assessment of anchorage in corroded reinforced concrete structures. Current research aims to extend the 1D model to comprise more practical situations. To verify the 1D model for various cases appearing in practice, such as multiple layers and bundled reinforcement, 3D analyses were carried out. The size of 3D NLFE models required to capture the bond behaviour between corroded reinforcement and concrete is investigated, this to enable efficient analyses. Beam-end models and models of sub-sections with varying sizes and boundary conditions were studied, and the results in terms of bond stress and crack pattern compared. Good agreement was found for several section models; however the choice of boundary conditions largely influence the results and can lead to overestimation of the capacity.
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| 2. |
- Blomfors, Mattias, 1990, et al.
(författare)
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Digitala tvillingmodeller underlättar bedömning av risker
- 2019
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Ingår i: Samhällsbyggaren. - 2000-2408. ; , s. 24-25
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Tidskriftsartikel (populärvet., debatt m.m.)abstract
- Digitala tvillingmodeller är digitala simuleringar som kombinerar information om en fysisk verklighet med avancerade beräkningsmodeller. I ett pågående samarbete mellan Chalmers och Stanford utvecklas digitala tvillingmodeller av broar, vilket kommer att leda till förbättrade tillståndsbedömningar och beslutsunderlag i framtiden; se digitaltwinslab.com.
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| 3. |
- Blomfors, Mattias, 1990, et al.
(författare)
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Engineering bond model for corroded reinforcement
- 2018
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Ingår i: Engineering structures. - : Elsevier BV. - 0141-0296 .- 1873-7323. ; 156, s. 394-410
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Tidskriftsartikel (refereegranskat)abstract
- Corrosion of the reinforcement in concrete structures affects their structural capacity. This problem affects many existing concrete bridges and climate change is expected to worsen the situation in future. At the same time, assessment engineers lack simple and reliable calculation methods for assessing the structural capacity of structures damaged by corrosion. This paper further develops an existing model for assessing the anchorage capacity of corroded reinforcement. The new version is based on the local bond stress-slip relationships from fib Model Code 2010 and has been modified to account for corrosion. The model is verified against a database containing the results from nearly 500 bond tests and by comparison with an empirical model from the literature. The results show that the inherent scatter among bond tests is large, even within groups of similar confinement and corrosion level. Nevertheless, the assessment model that has been developed can represent the degradation of anchorage capacity due to corrosion reasonably well. This new development of the model is shown to represent the experimental data better than the previous version; it yields similar results to an empirical model in the literature. In contrast to many empirical models, the model developed here represents physical behaviour and shows the full local bond stress-slip relationship. Using this assessment model will increase the ability of professional engineers to estimate the anchorage capacity of corroded concrete structures.
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| 4. |
- Blomfors, Mattias, 1990, et al.
(författare)
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Incorporation of cracks in finite element modelling of existing concrete structures
- 2019
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Ingår i: Structural Health Monitoring 2019: Enabling Intelligent Life-Cycle Health Management for Industry Internet of Things (IIOT) - Proceedings of the 12th International Workshop on Structural Health Monitoring. - Lancaster, PA : DEStech Publications, Inc.. ; 1, s. 1611-1618
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Konferensbidrag (refereegranskat)abstract
- Transport infrastructures are fundamental in society and interruption in their service leads to large economic losses. However, inspection and maintenance work of said infrastructures need to be performed to ensure their safety, which traditionally involves limitation or interruption of their use. This paper treats the finite element modelling part of a framework for non-intrusive assessment of existing structures. In practice, the load history of a structure is rarely known in detail. Here, existing cracks due to previous loading is included from the start of the finite element (FE) analysis to circumvent this issue. The focus is on comparing the choice of different shear retention factors for discrete cracks based on comparison to experimental test results. The results indicate that the shear retention factor used for the discrete cracks does not influence the capacity, which remains the same for all considered values. It appears the anchorage force development of the bond-slip reinforcement does not rely on shear transfer in the discrete crack in the adopted FE model. Moreover, the results showed that combining both discrete cracks and abond-slip relation implicitly including the loss of confinement due to corrosion-induced splitting cracks leads to excessively low capacity compared to experimentalresults. From the present study it can be concluded that the shear retention factor is of little importance for the considered FE model. However, it is emphasized that other modelling choices may entail other findings.
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| 5. |
- Blomfors, Mattias, 1990, et al.
(författare)
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Practical bond model for corroded RC bridges
- 2017
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Ingår i: High Tech Concrete. - Cham : Springer International Publishing. - 2617-4820. - 9783319594705 ; , s. 1793-1803
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Konferensbidrag (refereegranskat)abstract
- Corrosion of steel reinforcement is a common cause of deterioration in reinforced concrete bridges and many existing bridges are damaged to varying degrees. The rate of deterioration of the bridge stock has been shown to increase due to climate change. Unsympathetically, the demand for load-carrying capacity is however often increased with time. Therefore there is an increasing need for reliable methods to assess the load-carrying capacity and remaining service-life of existing infrastructure. A simple model for the assessment of Anchorage in corroded Reinforced Concrete structures (ARC) has previously been developed. It was originally based on fib Model Code 1990 and has been verified with experiments and three-dimensional nonlinear finite element (3D NLFE) analyses for both accelerated and natural corrosion as well as for different degrees of corrosion. The model was applied when assessing two road bridges in Sweden. The investigation demonstrated great cost savings but also areas for improvement, in particular regarding (a) applicability to practical cases and (b) incorporation of uncertainties in the assessment. The primary focal point of this paper is to present an overview of the development of the ARC model together with recent verifications against a large bond test database as well as foreseen future developments. It was found that the ARC model represents the physical behaviour reasonably well, and gives conservative values of bond strength compared to the bond tests database. In future works, among others, uncertainties of the input variables will be incorporated by means of probabilistic modelling, making way for implementation of the ARC model into semi-probabilistic safety concepts by extraction of modification factors. Overall, with more accurate and reliable assessment methods for corroded RC structures, environmental and economic savings are imminent as more of the potential of existing structures can be realized.
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| 6. |
- Blomfors, Martin, et al.
(författare)
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Reliability analysis of corroded reinforced concrete beam with regards to anchorage failure
- 2019
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Ingår i: Life-Cycle Analysis and Assessment in Civil Engineering. - : CRC Press/Balkema. - 9781138626331 - 9781351857574 ; , s. 337-344, s. 337-344
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Konferensbidrag (refereegranskat)abstract
- Reinforcement corrosion is a common problem in reinforced concrete infrastructure today, and it is expected to increase in the future. To simply replace the corroded structures with new ones requires large resources, both in financial and environmental terms. Therefore it is important that existing structures are used to their full potential, also after the onset of corrosion. This paper presents a reliability study of the anchorage capacity of a reinforced concrete beam including reinforcement corrosion. The sensitivity of the different input parameters is also studied. As expected, the results show that the reliability is reduced with corrosion; the magnitude depends to a large extent on the modelling uncertainty used for the bond model for corroded reinforcement. The sensitivity analysis shows an influence of corrosion also on the sensitivities of the input parameters, which is expected based on the properties of the underlying bond model. This paper demonstrates that probabilistic evaluations give valuable insight of the reliability, which can be used to prolong the service-life of existing infrastructure and save both money and the environment.
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| 7. |
- Blomfors, Mattias, 1990, et al.
(författare)
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Reliable engineering assessments of corroded concrete structures
- 2017
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Ingår i: Nordic Concrete Research : Proceedings of the XXIII Nordic Concrete Research Symposium, Aalborg, Denmark, 21-23 August, 2017 - Proceedings of the XXIII Nordic Concrete Research Symposium, Aalborg, Denmark, 21-23 August, 2017. ; , s. 245-248
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Konferensbidrag (refereegranskat)abstract
- Corrosion of steel reinforcement is a large and increasing problem for reinforced concrete structures. Simple and reliable assessment methods are required to use the full capacity of existing infrastructure. In this paper, a reliable engineering assessment method is outlined. A model for anchorage has been developed and verified against a large database of bond tests. Also the influence of corrosion on the bending and shear capacity is to be included, and a probabilistic model will be established. The outcome of this work will enable practising engineers to perform reliable assessments of concrete structures with corroded reinforcement.
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| 8. |
- Coronelli, Dario, et al.
(författare)
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FIB model code 2020 - Structural models for existing concrete structures
- 2018
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Ingår i: FIB 2018 - Proceedings for the 2018 fib Congress: Better, Smarter, Stronger. - 2617-4820. ; , s. 3019-3040
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Konferensbidrag (refereegranskat)abstract
- The paper gives an overview of this ambitious project, which builds upon the achievements of fib MC2010, the previous edition of the fib Model Code. MC2020 will deal with both the design of new structures and all the activities associated with the through-life management and care of existing concrete structures, including matters such as inservice assessment and interventions to extend the life / improve the performance of these structures. Particular attention will be paid to issues specific to existing structures. Relevant structural models are planned for the determination of their load capacity / structural reliability, serviceability, remaining service life etc taking account of: • Load-carrying behaviour not considered in design, such as compressive membrane action and the increase in concrete compressive strength with time due to ongoing hydration effects. • Load-carrying behaviour in deteriorated members and structures, which is different to those members which have not experienced deterioration. The paper gives consideration to corrosion of reinforced concrete members and prestressed concrete members, as well as to the effects of other forms of deterioration such as alkali-aggregate reactions and frost damage. The paper also notes some of the differences between the approaches employed for Life Cycle Assessment and Design (LCA / LCD) based on deterioration models, and the assessment of the present condition of the structure (i.e. at a given moment in time) which utilise mechanical models to represent the influences of the deterioration processes which are active.
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| 9. |
- E. Ransom, Elliot, et al.
(författare)
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A UAV-based platform for automated inspection of cracked concrete surfaces
- 2019
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Ingår i: Structural Health Monitoring 2019: Enabling Intelligent Life-Cycle Health Management for Industry Internet of Things (IIOT) - Proceedings of the 12th International Workshop on Structural Health Monitoring. - Lancaster, PA : DEStech Publications, Inc..
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Konferensbidrag (refereegranskat)
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| 10. |
- Fahimi, Shayan, et al.
(författare)
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Replication of Crack Pattern in FE Analysis Based on Discretization of Tension Softening Curves
- 2017
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Ingår i: Nordic Concrete Research. - 0800-6377. ; 56:1, s. 1-9
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Tidskriftsartikel (refereegranskat)abstract
- Today, there is an increasing need for reliable methods for condition assessment and service-life evaluation of existing structures. Although advanced 3D Nonlinear Finite Element (3D NLFE) analysis has proven to be capable of describing the behavior of reinforced concrete in a comprehensive way, the analysis results are difficult to couple with visual inspection data such as cracking and spalling. Moreover, 3D NLFE programs are numerically expensive and incomprehensible for full-scale practical applications. Thus, the present study aims to couple 3D NLFE analysis with condition assessment data, and consequently to increase the accuracy, to optimize the computation time and to improve robustness of such analyses.
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