Change search
Link to record
Permanent link

Direct link
Elfgren, Lennart, Senior ProfessorORCID iD iconorcid.org/0000-0002-0560-9355
Alternative names
Biography [eng]

Lennart Elfgren was born on July 9, 1942, in Gothenburg, Sweden. He studied civil engineering at Chalmers University of Technology and obtained a M.Sc. in 1965 and a PhD in 1971 on torsion-shear-bending in rc structures.

After a post doc stay at University of California at Berkeley 1972-73 working with curved box-girder bridges he was appointed to a position as Associate Professor in Structural Engineering at the recently started Luleå University of Technology. In 1981-83 he worked as a Consulting Engineer with Jacobson & Widmark (now WSP) in Gothenburg and in 1982-83 as part time Researcher in the Swedish Research and Testing Institute (now RISE) in Borås.

He returned to Luleå as Full Professor in 1983 and has served as Department Head and Dean of the Faculty of Engineering Sciences. He has been the main supervisor for 14 PhDs and an associate supervisor for another 15.

Publications (10 of 391) Show all publications
Min, X., Zhang, J., Tu, Y., Li, X., Wang, C., Sas, G. & Elfgren, L. (2024). A full-range fatigue life prediction model for RC beams strengthened with prestressed CFRP plates accounting for the impact of FRP debonding. Engineering structures, 301, Article ID 117305.
Open this publication in new window or tab >>A full-range fatigue life prediction model for RC beams strengthened with prestressed CFRP plates accounting for the impact of FRP debonding
Show others...
2024 (English)In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 301, article id 117305Article in journal (Refereed) Published
Place, publisher, year, edition, pages
Elsevier, 2024
National Category
Infrastructure Engineering
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-103512 (URN)10.1016/j.engstruct.2023.117305 (DOI)2-s2.0-85179467577 (Scopus ID)
Note

Validerad;2024;Nivå 2;2024-01-19 (signyg)

Funder: Natural Science Foundation of Jiangsu Province of China (grant nos. BK20230703); the Scientific Research Foundation of Nanjing Institute of Technology (grant nos. YKJ202122); the Natural Science Foundation of the Jiangsu Higher Education Institutions of China (23KJB560010); National Key Research and Development Program of China (grant nos. 2017YFC0703006-01); Array (2017YFC0703006-01)

Available from: 2024-01-08 Created: 2024-01-08 Last updated: 2024-02-01Bibliographically approved
Fang, M., Wang, T., Guo, T., Shi, P., Jiang, B., Wang, C., . . . Elfgren, L. (2024). Compressive reactive molecular dynamics on mechanical and structural behaviors of geopolymers: Imposing lateral constraints and varied temperatures. Applied Clay Science, 249, Article ID 107257.
Open this publication in new window or tab >>Compressive reactive molecular dynamics on mechanical and structural behaviors of geopolymers: Imposing lateral constraints and varied temperatures
Show others...
2024 (English)In: Applied Clay Science, ISSN 0169-1317, E-ISSN 1872-9053, Vol. 249, article id 107257Article in journal (Refereed) Published
Place, publisher, year, edition, pages
Elsevier Ltd, 2024
National Category
Other Materials Engineering
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-103908 (URN)10.1016/j.clay.2024.107257 (DOI)2-s2.0-85182403837 (Scopus ID)
Note

Validerad;2024;Nivå 2;2024-02-16 (joosat);

Funder: National Natural Science Foundation of China (51378104, U23A20661); Jiangsu Province (BZ2021011); Fundamental Research Funds for the Central Universities (2242022k30030, 2242022k30031); National Science Fund for Distinguished Young Scholars (52125802);

Available from: 2024-01-24 Created: 2024-01-24 Last updated: 2024-02-16Bibliographically approved
Wang, T., Cao, J., Guo, T., Tu, Y., Wang, C., Sas, G. & Elfgren, L. (2024). The role of deep learning in reducing computational cost when simulating chloride ion attack on hydrated calcium silicate with molecular dynamics. Construction and Building Materials, 417, Article ID 135257.
Open this publication in new window or tab >>The role of deep learning in reducing computational cost when simulating chloride ion attack on hydrated calcium silicate with molecular dynamics
Show others...
2024 (English)In: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 417, article id 135257Article in journal (Refereed) Published
Place, publisher, year, edition, pages
Elsevier Ltd, 2024
National Category
Other Civil Engineering
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-104320 (URN)10.1016/j.conbuildmat.2024.135257 (DOI)2-s2.0-85184522280 (Scopus ID)
Note

Validerad;2024;Nivå 2;2024-02-20 (joosat);

Funder: Natural Science Foundation of China [grant numbers 51378104]; National Science Fund for Distinguished Young Scholars [grant numbers 52125802]; "One belt, one road" innovation cooperation project, Jiangsu Province [grant numbers BZ2021011]; Fundamental Research Funds for the Central Universities [grant numbers 2242022k30030, 2242022k30031];

Available from: 2024-02-20 Created: 2024-02-20 Last updated: 2024-02-20Bibliographically approved
Min, X., Zhang, J., Li, X., Wang, C., Tu, Y., Sas, G. & Elfgren, L. (2023). A nonlinear prediction model of the debonding process of an FRP-concrete interface under fatigue loading. Construction and Building Materials, 369, Article ID 130583.
Open this publication in new window or tab >>A nonlinear prediction model of the debonding process of an FRP-concrete interface under fatigue loading
Show others...
2023 (English)In: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 369, article id 130583Article in journal (Refereed) Published
Abstract [en]

Externally bonded Fiber Reinforced Polymer (FRP) strengthening has been proven to be an efficient and reliable method for structural strengthening of reinforced concrete (RC) members. However, the beneficial effects of this method can be diminished due to the debonding of the FRP laminates. The mechanism of FRP debonding still requires further research, especially for strengthened members under fatigue loading. To understand and predict the FRP fatigue debonding process better, eleven FRP-concrete joint specimens were tested under static or fatigue loading. Both the theoretical derivation and the experimental study indicated that the debonding growth rate of the FRP laminate depended not only on the mean level (), but also the amplitude () of the applied fatigue load. In addition, the debonded portion of the FRP laminate had a significant impact on the following debonding process due to the friction and mechanical interaction between the debonded FRP and the concrete surface. Therefore, a new nonlinear prediction model is proposed in this paper. The proposed model explicitly took into account the amplitude and the mean level of the fatigue loading, which enabled the effect of both to be modelled. Meanwhile, a correction term was also introduced into the model to account for the influence of the previously debonded FRP laminate. The predicted results of the debonding growth rate and the debonding length agreed well with the experimental results.

Place, publisher, year, edition, pages
Elsevier Ltd, 2023
Keywords
Concrete, Debond, Fatigue, Fiber Reinforced Polymer, Interface
National Category
Composite Science and Engineering
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-95675 (URN)10.1016/j.conbuildmat.2023.130583 (DOI)000946205000001 ()2-s2.0-85147606490 (Scopus ID)
Note

Validerad;2023;Nivå 2;2023-02-21 (joosat);

Funder: Scientific Research Foundation of Nanjing Institute of Technology (YKJ202122); National Key Research and Development Program of China (No. 2017YFC0703006-01)

Available from: 2023-02-21 Created: 2023-02-21 Last updated: 2023-04-21Bibliographically approved
Liu, D., Wang, C., Gonzalez-Libreros, J., Guo, T., Cao, J., Tu, Y., . . . Sas, G. (2023). A review of concrete properties under the combined effect of fatigue and corrosion from a material perspective. Construction and Building Materials, 369, Article ID 130489.
Open this publication in new window or tab >>A review of concrete properties under the combined effect of fatigue and corrosion from a material perspective
Show others...
2023 (English)In: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 369, article id 130489Article, review/survey (Refereed) Published
Abstract [en]

When in use, reinforced concrete bridge structures not only experience high-frequency fatigue loading caused by passing vehicles, but also suffer from the effects of a corrosive environment. In addition to fatigue damage to reinforcement, long-term fatigue loading also causes concrete cracking and deterioration of pore structures, thereby accelerating the ingress of external corrosive substances and reducing concrete durability. Long-term exposure to a corrosive environment also reduces the performance of concrete and causes corrosion of reinforcement materials, affecting the fatigue performance of the structure. Therefore, there is a combined effect between fatigue loads and corrosion on concrete. This paper is a review of the current literature from a material perspective on the performance degradation of concrete under the combined action of fatigue loading and corrosion, that is, carbonation, chloride ion attack, freeze–thaw cycles, and sulphate attack. The paper includes (1) a description of a test method for examining the combined action of fatigue loading and corrosion, (2) a summary of performance degradation of concrete under the combined effect of fatigue loading and corrosion, and (3) an introduction to durability deterioration models considering fatigue damage, and fatigue models that can account for corrosion. Finally, potential future research on concrete under the combined effect of fatigue loading and corrosion is described.

Place, publisher, year, edition, pages
Elsevier, 2023
Keywords
Concrete, Fatigue load, Corrosion, Combined action, Carbonation, Chloride attack, Freeze–thaw cycles, Sulphate attack, Deterioration, Modelling
National Category
Infrastructure Engineering
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-95539 (URN)10.1016/j.conbuildmat.2023.130489 (DOI)000927776800001 ()2-s2.0-85147195723 (Scopus ID)
Funder
Swedish Transport Administration
Note

Validerad;2023;Nivå 2;2023-02-08 (hanlid);

Funder: FOI-BBT program (BBT-2019-022)

Available from: 2023-02-08 Created: 2023-02-08 Last updated: 2023-04-21Bibliographically approved
Liu, D., Wang, C., Gonzalez-Libreros, J., Tu, Y., Elfgren, L. & Sas, G. (2023). A review on aerodynamic load and dynamic behavior of railway noise barriers when high-speed trains pass. Journal of Wind Engineering and Industrial Aerodynamics, 239, Article ID 105458.
Open this publication in new window or tab >>A review on aerodynamic load and dynamic behavior of railway noise barriers when high-speed trains pass
Show others...
2023 (English)In: Journal of Wind Engineering and Industrial Aerodynamics, ISSN 0167-6105, E-ISSN 1872-8197, Vol. 239, article id 105458Article in journal (Refereed) Published
Abstract [en]

Noise barriers need to be installed along high-speed railway lines to protect nearby inhabitants from the noise pollution caused by the running of high-speed trains (HSTs). The vertical noise barrier is the main structural type. However, when an HST passes through the noise barriers sited along the track, significant and transient aerodynamic pressure will act on the surface of the noise barriers, resulting in strong dynamic responses and even fatigue damage. Therefore, it is important to determine the train-induced aerodynamic load on the barrier surface and analyze the dynamic behaviors of the noise barriers under such a load for its structural design and to guarantee its safety and durability. This paper is a systematic review of the current literature on the aerodynamic load and dynamic behavior of vertical noise barriers; it includes (1) a summary and analysis of characteristics of such aerodynamic pressure and relevant influencing factors, (2) an introduction to measurement methods of aerodynamic load and relevant pressure models on the surface of noise barriers, and (3) a description of the dynamic response and fatigue analysis of noise barriers under such loads. Finally, potential further studies on this topic are discussed, and conclusions are drawn.

Place, publisher, year, edition, pages
Elsevier, 2023
Keywords
Noise barrier, Railway, High-speed train, Aerodynamic load, Dynamic response, Fatigue
National Category
Vehicle Engineering
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-98162 (URN)10.1016/j.jweia.2023.105458 (DOI)2-s2.0-85160798389 (Scopus ID)
Funder
Swedish Transport Administration, “Excellence Area 4” and FOI-BBT program (grant number BBT-2019-022)
Note

Validerad;2023;Nivå 2;2023-06-12 (joosat);

Licens fulltext: CC BY License

Available from: 2023-06-12 Created: 2023-06-12 Last updated: 2023-10-12Bibliographically approved
Yu, Q., Lin, Y., Guo, T., Wen, R., Wang, C., Tu, Y., . . . Elfgren, L. (2023). Assessing the unsaturated transport and adsorption properties of ions in nanopores of realistic hydrated-calcium-silicate gel using molecular dynamics simulations. Computational materials science, 222, Article ID 112121.
Open this publication in new window or tab >>Assessing the unsaturated transport and adsorption properties of ions in nanopores of realistic hydrated-calcium-silicate gel using molecular dynamics simulations
Show others...
2023 (English)In: Computational materials science, ISSN 0927-0256, E-ISSN 1879-0801, Vol. 222, article id 112121Article in journal (Refereed) Published
Abstract [en]

The unsaturated transport of water and ions in concrete structures accelerates the corrosion of reinforcing steel bars. Unfortunately, previous macroscopic and microscopic experimental studies have provided little clarity on the transport mechanisms of ions in calcium-silicate-hydrate (C-S-H) gels. This paper presents molecular dynamics simulations performed to investigate the effect of ion species and concentration during unsaturated transport processes. The transport rate of NaCl solutions at any given concentration significantly exceeds that of CaCl2 solutions because of desorption of intralayer calcium ions in the substrate. Additionally, the electric double layer effect of the realistic C-S-H gel substrate is more pronounced in NaCl solution than in CaCl2 solution and becomes stronger as the concentration increases in both cases. These insights into the effects of ion species and concentration on unsaturated ion transport and adsorption in realistic C-S-H gel nanopores will help guide the development of cement-based materials with improved corrosion resistance.

Place, publisher, year, edition, pages
Elsevier B.V., 2023
Keywords
Adsorption properties, Calcium silicate hydrate, Molecular dynamics simulation, Unsaturated transport
National Category
Physical Chemistry Materials Chemistry
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-96187 (URN)10.1016/j.commatsci.2023.112121 (DOI)2-s2.0-85149757816 (Scopus ID)
Note

Validerad;2023;Nivå 2;2023-03-20 (joosat);

Funder: National Natural Science Foundation of China (grant no. 51378104); National Science Fund for Distinguished Young Scholars (grant no. 52125802); “One belt, one road” innovation cooperation project, Jiangsu Province (grant no. BZ2021011)

Available from: 2023-03-20 Created: 2023-03-20 Last updated: 2023-04-21Bibliographically approved
Agredo Chavez, A. M., Ulfberg, A., Gonzalez-Libreros, J., Elfgren, L. & Sas, G. (2023). Data Validation of Strain-Based Monitoring Systems in Low Temperature Conditions, Case Study: The Kalix Bridge. In: Alper Ilki, Derya Çavunt, Yavuz Selim Çavunt (Ed.), Building for the Future: Durable, Sustainable, Resilient - Proceedings of the fib Symposium 2023 - Volume 2: . Paper presented at International Symposium of the International Federation for Structural Concrete, fib Symposium 2023, Istanbul, Turkey, June 5-7, 2023 (pp. 986-995). Springer, 2
Open this publication in new window or tab >>Data Validation of Strain-Based Monitoring Systems in Low Temperature Conditions, Case Study: The Kalix Bridge
Show others...
2023 (English)In: Building for the Future: Durable, Sustainable, Resilient - Proceedings of the fib Symposium 2023 - Volume 2 / [ed] Alper Ilki, Derya Çavunt, Yavuz Selim Çavunt, Springer, 2023, Vol. 2, p. 986-995Conference paper, Published paper (Refereed)
Abstract [en]

Over the last decades, economic growth and sustained development have enforced the need to ensure reliable and long-lasting infrastructure network to guarantee serviceability and safety. Nevertheless, detrimental effects can lead over time to insufficient structural performance under increasing service loadings and extreme events. Hence, Structural Health Monitoring (SHM) arises as a solution to cope with the need of having timely and continuous data to assess the state of crucial structural assets, such as prestressed concrete bridges. On this matter, the validation of the retrieved data becomes essential for the risk-based decision making in the assessment of bridges, where selecting the most suitable monitoring system could allow to addressed main causes to the right phenomena of deterioration during the service life of the bridge. Consistently with these efforts, this paper deals with a comparative study between the data acquired by different strain-based sensors such as Fiber optic systems (FOS) and strain gauges that were installed to monitor a proof loading test developed on a 65-year-old balanced cantilever prestressed concrete bridge located in Northern Sweden. The monitored data led to establish main differences between emerging types of monitoring systems such as FOS to the well-based strain gauges when exposed to low temperature conditions. Conclusions regarding the influencing parameters between both retrieved data are drawn when evaluating the structural response under serviceability loading conditions is performed, supporting decision makers when different levels of structural assessment are required.

Place, publisher, year, edition, pages
Springer, 2023
Series
Lecture Notes in Civil Engineering, ISSN 2366-2557, E-ISSN 2366-2565 ; 350
Keywords
Assessment, proof loading test, strain-based monitoring, prestressed concrete bridges, instrumentation, low temperature conditions, Sensor Validation Tools (SVTs)
National Category
Infrastructure Engineering
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-99640 (URN)10.1007/978-3-031-32511-3_101 (DOI)2-s2.0-85164265346 (Scopus ID)978-3-031-32510-6 (ISBN)978-3-031-32511-3 (ISBN)
Conference
International Symposium of the International Federation for Structural Concrete, fib Symposium 2023, Istanbul, Turkey, June 5-7, 2023
Available from: 2023-08-14 Created: 2023-08-14 Last updated: 2023-08-14Bibliographically approved
Daescu, C. A., Gonzalez-Libreros, J., Wang, C., Elfgren, L. & Sas, G. (2023). Demolition of a 65-year-old box-girder prestressed concrete bridge located in Northern Sweden. In: Alfred Strauss; Konrad Bergmeister (Ed.), EuroStruct 2023 European Association on Quality Control of  Bridges and Structures: Digital Transformation in Sustainability: . Paper presented at EUROSTRUCT2023 - 2nd Conference of the European Association on Quality Control of Bridges and Structures, Vienna, Austria, September 25-29, 2023 (pp. 229-234). John Wiley & Sons
Open this publication in new window or tab >>Demolition of a 65-year-old box-girder prestressed concrete bridge located in Northern Sweden
Show others...
2023 (English)In: EuroStruct 2023 European Association on Quality Control of  Bridges and Structures: Digital Transformation in Sustainability / [ed] Alfred Strauss; Konrad Bergmeister, John Wiley & Sons, 2023, p. 229-234Conference paper, Published paper (Refereed)
Abstract [en]

A new bridge was built in Kalix, northern Sweden, to replace an existing prestressed concrete box-girder bridge that had been in service for over 60 years. The old bridge had a total length of 283.6 m divided into five spans: 43.9 m, 47.0 m, 94.0 m, 47.0 m, and 43.9 m. It was constructed using the balanced cantilever method with segments having lengths of around 3.0 m. The need for replacement arose from recommendations extracted from an assessment of the old bridge's state and capacity. In addition to the construction of the new bridge, its replacement necessitated the creation and evaluation of demolition procedure for the existing bridge. This procedure had to be carefully designed to avoid damaging the new bridge and stability-related issues but also to prevent debris from falling into the Kalix River, which is part of a Natura 2000 protected area. This paper discusses various issues considered while developing the demolition strategy, including the use of bed-rock anchored tendons, intermediate support fixing at specific locations, and proper evaluation of position of the demolition equipment supported by the bridge, among others. The problem of disposing of the demolished material is also discussed.

Place, publisher, year, edition, pages
John Wiley & Sons, 2023
Series
ce/papers - Proceedings in Civil Engineering, E-ISSN 2509-7075 ; 6:5
Keywords
Bridge, Demolition, Waste Disposal, Deconstruction, Tendons, Anchoring System
National Category
Infrastructure Engineering
Identifiers
urn:nbn:se:ltu:diva-103664 (URN)10.1002/cepa.2745 (DOI)
Conference
EUROSTRUCT2023 - 2nd Conference of the European Association on Quality Control of Bridges and Structures, Vienna, Austria, September 25-29, 2023
Note

Funder: NCC  Infrastructure, Civil Engineering Division, Sweden;

Full text license: CC BY

Available from: 2024-01-15 Created: 2024-01-15 Last updated: 2024-01-15Bibliographically approved
Cao, J., Wang, C., Wang, T., Gonzalez-Libreros, J., Tu, Y., Sas, G. & Elfgren, L. (2023). Effects of Temperature and NaCl Concentration on the Adsorption of C-S-H Gel in Cement Paste: A Multi-fidelity Molecular Dynamics Simulation. In: Alper Ilki, Derya Çavunt, Yavuz Selim Çavunt (Ed.), Building for the Future: Durable, Sustainable, Resilient - Proceedings of the fib Symposium 2023 - Volume 2: . Paper presented at International Symposium of the International Federation for Structural Concrete, fib Symposium 2023, Istanbul, Turkey, June 5-7, 2023 (pp. 499-508). Springer, 2
Open this publication in new window or tab >>Effects of Temperature and NaCl Concentration on the Adsorption of C-S-H Gel in Cement Paste: A Multi-fidelity Molecular Dynamics Simulation
Show others...
2023 (English)In: Building for the Future: Durable, Sustainable, Resilient - Proceedings of the fib Symposium 2023 - Volume 2 / [ed] Alper Ilki, Derya Çavunt, Yavuz Selim Çavunt, Springer, 2023, Vol. 2, p. 499-508Conference paper, Published paper (Refereed)
Abstract [en]

The durability and compressive strength of concrete will vary with the material components, ambient temperature, external intrusion. Using molecular dynamics (MD) methods to study the dynamic behavior of particles in cement-based materials can help us understand the underlying mechanism of property changes in concrete caused by above factors at the atomic level. So far, MD methods have been widely used to analyze the physical and chemical properties of concrete materials and the interaction mechanism between different interfaces at the nanoscale. However, too much complexity in the models will reduce the result accuracy and increase the computational cost. A suitable neural network structure can not only ensure the accuracy of analysis results, but also reduce the computational cost. In this work, MD methods are applied to build the models to explore the diffusivity of Na+ and Cl− in the calcium silicate hydrate (C-S-H) gel pores at different concentration and temperatures. In the process of running models, part of the MD models’ fidelity is reduced to save the computational cost, then the trained multi-fidelity physics informed neural network framework was used to obtain more accurate analysis results. The combination of MD simulations and deep learning methods expands the application range of MD in the field of concrete structure, has good development prospect and application value.

Place, publisher, year, edition, pages
Springer, 2023
Series
Lecture Notes in Civil Engineering, ISSN 2366-2557, E-ISSN 2366-2565 ; 350
Keywords
Multi-fidelity Model, Molecular Dynamics, C-S-H Gel, Ion diffusion
National Category
Construction Management
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-99604 (URN)10.1007/978-3-031-32511-3_53 (DOI)2-s2.0-85164267102 (Scopus ID)978-3-031-32510-6 (ISBN)978-3-031-32511-3 (ISBN)
Conference
International Symposium of the International Federation for Structural Concrete, fib Symposium 2023, Istanbul, Turkey, June 5-7, 2023
Available from: 2023-08-14 Created: 2023-08-14 Last updated: 2023-08-14Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-0560-9355

Search in DiVA

Show all publications