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Popescu, C., Mirzazade, A., Ohlsson, U., Sas, G. & Häggström, J. (2021). Bridge inspections using unmanned aerial vehicles – A case study in Sweden. Luleå: Luleå University of Technology
Open this publication in new window or tab >>Bridge inspections using unmanned aerial vehicles – A case study in Sweden
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2021 (English)Report (Other academic)
Abstract [en]

The aim of the current project is to digitalize inspections and monitoring of structures’ health using drones in order to identify and allow for easier inspection of damages in transport infrastructure. The objectives set are to perform aerial photogrammetry to recreate the as-is condition to enable off-site inspection of difficult to reach areas in structures and identify damages – e.g. cracks, spalling, corrosion. The drone is controlled either autonomously or with the use of a remote control by a pilot from the ground. The drone can carry a wide range of imaging technologies including still, video and infrared sensors. The high flexibility and accessibility of drones in hard-to-reach or risk exposed areas makes the airborne photogrammetry a better alternative to the ground-based method. Given the potential of UAVs to help bridge inspectors performing inspections off-site, the Swedish Transport Administration developed a demonstration project to evaluate the effectiveness and future opportunities within inspection field. Five bridges of varying sizes and types were selected as demonstrators. Data collection including the 3D model creation has been performed by three different contractors while the model-based inspection for all bridges was performed by the same team. It has been shown that the 3D models could serve as a tool for bridge inspectors from which measurements could be extracted and certain damages identified. A full off-site inspection is currently not feasible as some areas of the bridges were difficult to capture. The models are only providing near-surface information, and therefore, in-depth inspection should not be overlooked. The difficulty to capture local defects such as delaminations and narrow cracks also reduces versatility. The main conclusion from the study is that drones cannot be used independently to conduct inspections. Currently, they can only be used as a complement to traditional inspections. The added value of a 3D model derives from the possibility of using it as tool to better plan large inspections in the field and/or future maintenance work.

Place, publisher, year, edition, pages
Luleå: Luleå University of Technology, 2021. p. 37
Series
Technical report / Luleå University of Technology, ISSN 1402-1536
Keywords
Drone inspection, Bridge inspections, Unmanned aerial vehicles
National Category
Infrastructure Engineering
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-83454 (URN)978-91-7790-814-2 (ISBN)
Available from: 2021-03-30 Created: 2021-03-30 Last updated: 2023-10-20Bibliographically approved
Huang, Z., Tu, Y., Meng, S., Ohlsson, U., Täljsten, B. & Elfgren, L. (2020). A practical method for predicting shear deformation of reinforced concrete beams. Engineering structures, 206, Article ID 110116.
Open this publication in new window or tab >>A practical method for predicting shear deformation of reinforced concrete beams
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2020 (English)In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 206, article id 110116Article in journal (Refereed) Published
Abstract [en]

This paper presents a practical method for predicting the deflections, including both the flexure and shear contributions, of reinforced concrete (RC) beams. The shear force - shear strain (V-γ) curve of a section in the shear span of RC beams is represented by a piecewise model and the tangent shear stiffness after shear cracking, Kt,cr, is assumed to be constant. A 2D finite element model, which has been validated for predicting shear deformation of RC beams, was used to identify factors that may affect the shear reduction factor (the ratio of Kt,cr to the elastic shear stiffness) and establish methodology for predicting the V-γ curve. Two types of methods, integration-form and closed-form, for predicting the total deflection were developed, in which the flexure-induced deflection (FD) was predicted using the Bischoff model while the shear-induced deflection (SD) was predicted using the method proposed in this paper. Comparison of the predictions with experimental results confirms that the Bischoff model provides reliable predictions of FDs of RC beams with and without shrinkage. It also shows that the proposed method can provide accurate predictions for SD after shear cracking, provided the effect of shrinkage on the shear cracking load is adequately quantified.

Support from: National Natural Science Foundation of China (No. 51378104) and A Project Funded by the Priority Academic Program Development ofJiangsu Higher Education Institutions. The Development Fund of the Swedish Construction Industry (SBUF), the Swedish Research Council Formas and Elsa and Sven Thysell Foundation

Place, publisher, year, edition, pages
Elsevier, 2020
Keywords
concrete, shear deformations, practical method
National Category
Infrastructure Engineering Other Civil Engineering
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-77439 (URN)10.1016/j.engstruct.2019.110116 (DOI)000510609900004 ()2-s2.0-85077227485 (Scopus ID)
Funder
Svenska Byggbranschens Utvecklingsfond (SBUF)Swedish Research Council Formas
Note

Validerad;2020;Nivå 2;2020-01-23 (johcin)

Available from: 2020-01-16 Created: 2020-01-16 Last updated: 2023-09-06Bibliographically approved
Sabourova, N., Duvnjak, I., Grip, N., Damjanovic, D., Tu, Y., Popescu, C., . . . Elfgren, L. (2020). Detection of sparse damages in plates. In: Jan Bień, Jan Biliszczuk, Paweł Hawryszków, Maciej Hildebrand, Marta Knawa-Hawryszków, Krzysztof Sadowski (Ed.), IABSE Symposium, Wroclaw 2020: Synergy of Culture and Civil Engineering – History and Challenges. Paper presented at IABSE Symposium “Synergy of Culture and Civil Engineering – History and Challenges”, 7-9 October, 2020, Wrocław, Poland (pp. 1141-1148). Zürich: International Association For Bridge And Structural Engineering (IABSE)
Open this publication in new window or tab >>Detection of sparse damages in plates
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2020 (English)In: IABSE Symposium, Wroclaw 2020: Synergy of Culture and Civil Engineering – History and Challenges / [ed] Jan Bień, Jan Biliszczuk, Paweł Hawryszków, Maciej Hildebrand, Marta Knawa-Hawryszków, Krzysztof Sadowski, Zürich: International Association For Bridge And Structural Engineering (IABSE) , 2020, p. 1141-1148Conference paper, Published paper (Refereed)
Abstract [en]

Structural damage is often a spatially sparse phenomenon, i.e. it occurs only in a small part of the structure. This property of damage has not been utilized in the field of structural damage identification until quite recently, when the sparsity-based regularization developed in compressed sensing problems found its application in this field. In this paper we consider classical sensitivity-based finite element model updating combined with a regularization technique appropriate for the expected type of sparse damage. The validity of the proposed methods is demonstrated using simulations on a bridge. The pros and cons of these methods are discussed.

Place, publisher, year, edition, pages
Zürich: International Association For Bridge And Structural Engineering (IABSE), 2020
Keywords
Damage Detection, Sparse Damage, FEM Updating, Regularization
National Category
Other Civil Engineering Mathematical Analysis
Research subject
Structural Engineering; Applied Mathematics
Identifiers
urn:nbn:se:ltu:diva-81136 (URN)2-s2.0-85103443479 (Scopus ID)
Conference
IABSE Symposium “Synergy of Culture and Civil Engineering – History and Challenges”, 7-9 October, 2020, Wrocław, Poland
Note

ISBN för värdpublikation: 978-3-85748-169-7

Available from: 2020-10-14 Created: 2020-10-14 Last updated: 2022-12-30Bibliographically approved
Nilforoush, R., Nilimaa, J., Bagge, N., Puurula, A., Ohlsson, U., Nilsson, M., . . . Elfgren, L. (2020). Fracture energy of concrete for bridge assessment. In: Jan Bien; Jan Biliszczuk; Pawel Hawryszkow; Maciej Hildebrand; Marta Knawa-Hawryszkow; Krzysztof Sadowski (Ed.), 1st IABSE Online Symposium 2020: Synergy of Culture and Civil Engineering - History and Challenges. Paper presented at 1st IABSE Online Symposium 2020, Wroclaw, Poland (Online), October 7-9, 2020 (pp. 692-699). International Association for Bridge and Structural Engineering (IABSE)
Open this publication in new window or tab >>Fracture energy of concrete for bridge assessment
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2020 (English)In: 1st IABSE Online Symposium 2020: Synergy of Culture and Civil Engineering - History and Challenges / [ed] Jan Bien; Jan Biliszczuk; Pawel Hawryszkow; Maciej Hildebrand; Marta Knawa-Hawryszkow; Krzysztof Sadowski, International Association for Bridge and Structural Engineering (IABSE) , 2020, p. 692-699Conference paper, Published paper (Refereed)
Abstract [en]

In numerical assessments of concrete bridges, the value of the concrete fracture energy GF plays an important role. However, mostly the fracture energy is only estimated based on the concrete compressive strength using empirical formulae. In order to study methods to determine the concrete fracture energy for existing bridges, tests were carried out on 55-year-old concrete from a bridge tested to failure in Kiruna in northern Sweden. Uniaxial tensile tests are performed on notched cylindrical concrete cores drilled out from this and other bridges. In the paper, different methods to determine the concrete fracture energy are discussed and recommendations are given for assessment procedures.

Place, publisher, year, edition, pages
International Association for Bridge and Structural Engineering (IABSE), 2020
Keywords
Assessment of structures, Brittleness, Concrete modelling, Fracture energy, Three-point-bending test, Uniaxial tensile test
National Category
Infrastructure Engineering
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-85850 (URN)2-s2.0-85103462867 (Scopus ID)
Conference
1st IABSE Online Symposium 2020, Wroclaw, Poland (Online), October 7-9, 2020
Funder
Swedish Transport AdministrationLuleå University of Technology
Note

ISBN för värdpublikation: 978-385748169-7

Available from: 2021-06-22 Created: 2021-06-22 Last updated: 2023-09-05Bibliographically approved
Cyron, W., Nilsson, M., Emborg, M. & Ohlsson, U. (2019). Bonded Concrete Overlays: A Brief Discussion on Restrained Shrinkage Deformations and Their Prediction Models. Nordic Concrete Research, 61(2), 107-129
Open this publication in new window or tab >>Bonded Concrete Overlays: A Brief Discussion on Restrained Shrinkage Deformations and Their Prediction Models
2019 (English)In: Nordic Concrete Research, ISSN 0800-6377, Vol. 61, no 2, p. 107-129Article in journal (Refereed) Published
Abstract [en]

Bonded concrete overlays (BCO) on bridge decks are beneficial solutions due to their superior properties as compared to the typical asphalt pavement. A significant number of overlays suffer however, from occurrence of cracks and delamination due to poor bond, and restrained shrinkage and thermal dilation. Over the past years different appraisals for estimation of the restrained deformations have been developed, from micro-scale models, based on poromechanics, to empirical equations as given in B3 or B4 models suggested by Baiant. This paper provides a short overview of calculation models along with a brief theoretical explanation of shrinkage mechanism.

Place, publisher, year, edition, pages
Walter de Gruyter, 2019
Keywords
bridge, overlay, concrete, shrinkage, creep
National Category
Infrastructure Engineering
Research subject
Building Materials; Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-95682 (URN)10.2478/ncr-2019-0019 (DOI)000508428100007 ()
Note

Godkänd;2023;Nivå 0;2023-02-23 (hanlid)

Available from: 2023-02-23 Created: 2023-02-23 Last updated: 2023-09-05Bibliographically approved
Duvnjak, I., Damjanović, D., Sabourova, N., Grip, N., Ohlsson, U., Elfgren, L. & Tu, Y. (2019). Damage Detection in Structures – Examples. In: IABSE Symposium 2019: Towards a Resilent Built Environment - Risk and Asset Management. Paper presented at IABSE Symposium 2019, Towards a Resilient Built Environment - Risk and Asset Management, March 27-29, 2019, Guimarães, Portugal (pp. 471-478). nternational Association for Bridge and Structural Engineering (IABSE)
Open this publication in new window or tab >>Damage Detection in Structures – Examples
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2019 (English)In: IABSE Symposium 2019: Towards a Resilent Built Environment - Risk and Asset Management, nternational Association for Bridge and Structural Engineering (IABSE) , 2019, p. 471-478Conference paper, Published paper (Refereed)
Abstract [en]

Damage assessment of structures includes estimation of location and severity of damage. Quite often it is done by using changes of dynamic properties, such as natural frequencies, mode shapes and damping ratios, determined on undamaged and damaged structures. The basic principle is to use dynamic properties of a structure as indicators of any change of its stiffness and/or mass. In this paper, two new methods for damage detection are presented and compared. The first method is based on comparison of normalised modal shape vectors determined before and after damage. The second method uses so-called 𝑙1-norm regularized finite element model updating. Some important properties of these methods are demonstrated using simulations on a Kirchhoff plate. The pros and cons of the two methods are discussed. Unique aspects of the methods are highlighted.

Place, publisher, year, edition, pages
nternational Association for Bridge and Structural Engineering (IABSE), 2019
Keywords
mode shape damage detection, finite element model updating, 𝑙1-norm regularization
National Category
Engineering and Technology Mathematics Other Civil Engineering
Research subject
Mathematics; Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-73334 (URN)10.2749/guimaraes.2019.0471 (DOI)2-s2.0-85065261356 (Scopus ID)
Conference
IABSE Symposium 2019, Towards a Resilient Built Environment - Risk and Asset Management, March 27-29, 2019, Guimarães, Portugal
Available from: 2019-03-28 Created: 2019-03-28 Last updated: 2023-02-22Bibliographically approved
Sabourova, N., Grip, N., Ohlsson, U., Elfgren, L., Tu, Y., Duvnjak, I. & Damjanović, D. (2019). Detection of Sparse Damages in Structures. In: IABSE Symposium 2019: Towards a Resilent Built Environment - Risk and Asset Management. Paper presented at IABSE Symposium 2019 'Towards a Resilient Built Environment - Risk and Asset Management', 27-29 March, 2019, Guimarães, Portugal (pp. 515-522). International Association for Bridge and Structural Engineering (IABSE)
Open this publication in new window or tab >>Detection of Sparse Damages in Structures
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2019 (English)In: IABSE Symposium 2019: Towards a Resilent Built Environment - Risk and Asset Management, International Association for Bridge and Structural Engineering (IABSE) , 2019, p. 515-522Conference paper, Published paper (Refereed)
Abstract [en]

Structural damage is often a spatially sparse phenomenon, i.e. it occurs only in a small part of the structure. This property of damage has not been utilized in the field of structural damage identification until quite recently, when the sparsity-based regularization developed in the compressed sensing found its application in this field.

In this paper we consider classical sensitivity-based finite element model updating combined with a regularization technique appropriate for the expected type of sparse damage. Traditionally (1) 𝑙2-norm regularization was used to solve the ill-posed inverse problems, such as damage identification. However, using (2) already well established 𝑙1-norm regularization or (3) our proposed 𝑙1-norm total variation regularization and (4) general dictionary-based regularization allows us to find damages with special spatial properties quite precisely using much fewer measurement locations than the number of possibly damaged elements of the structure. The validity of the proposed methods is demonstrated using simulations on a Kirchhoff plate model. The pros and cons of these methods are discussed.

Place, publisher, year, edition, pages
International Association for Bridge and Structural Engineering (IABSE), 2019
Series
IABSE Symposium Report ; 114
Keywords
sparse damage, 𝑙2-norm, 𝑙1-norm, total variation, dictionary-based regularization, sensitivity
National Category
Mathematical Analysis Other Civil Engineering
Research subject
Mathematics; Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-73335 (URN)10.2749/guimaraes.2019.0515 (DOI)2-s2.0-85065234822 (Scopus ID)
Conference
IABSE Symposium 2019 'Towards a Resilient Built Environment - Risk and Asset Management', 27-29 March, 2019, Guimarães, Portugal
Note

ISBN för värdpublikation: 978-1-5108-8445-8

Available from: 2019-03-28 Created: 2019-03-28 Last updated: 2023-02-22Bibliographically approved
Sabourova, N., Grip, N., Tu, Y., Wang, C., Enochsson, O., Blanksvärd, T., . . . Elfgren, L. (2019). Railway Concrete Arch Bridge over Kalix River at Långforsen: Dynamic Properties and Load-Carrying Capacity. Luleå: Luleå University of Technology
Open this publication in new window or tab >>Railway Concrete Arch Bridge over Kalix River at Långforsen: Dynamic Properties and Load-Carrying Capacity
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2019 (English)Report (Refereed)
Abstract [en]

The concrete arch bridge over Kalix River at Långforsen was built in 1960 and has a mid-span of 89,5 m and a height of 13,7 m. The bridge owner, Trafikverket, wanted to increase its allowable axle load from 225 to 300 kN. Field tests were carried out under service condition and with ambient vibrations. The test results were used to update and validate Finite Element Models. At last, the refined models were used to check the possibility to increase the axle load.

According to earlier assessments, most parts of the bridge is capable of carrying an axle load of 330 kN. The only critical sections are located in the beams carrying the rail on top of the arch in the section where the beams are united with the arch. Here the stresses in the longitudinal bottom reinforcement are slightly too high.

These sections have been studied in a FEM model for different loads and results show maximum strains of about 50·10-6 corresponding to stresses of only about 10 MPa in the reinforcement in the critical sections. Live load vertical deflections of the crown of the arch is of the order of only ± 6 mm. Dynamic studies have also been made showing that fatigue is no issue. Altogether the studies show that the bridge is able to carry an increased axle load of 300 kN without problems.

Place, publisher, year, edition, pages
Luleå: Luleå University of Technology, 2019. p. 44
Series
Research report / Luleå University of Technology, ISSN 1402-1528
Keywords
Concrete Arch Bridge, Railway, Dynamic Properties, Load-Carrying Capacity
National Category
Infrastructure Engineering
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-76116 (URN)978-91-7790-473-1 (ISBN)
Funder
Swedish Transport Administration
Available from: 2019-09-25 Created: 2019-09-25 Last updated: 2023-09-05Bibliographically approved
Coric, I., Täljsten, B., Blanksvärd, T., Sas, G., Ohlsson, U. & Elfgren, L. (2018). Railway Bridges on the Iron Ore Line in Northern Sweden: From Axle Loads of 14 to 32,5 ton. In: IABSE Conference Copenhagen 2018: Engineering the Past, to Meet the Needs of the Future. Paper presented at IABSE Conference 2018 'Engineering the Past, to Meet the Needs of the Future', 25-27 June, 2018, Copenhagen, Denmark (pp. 55-62). International Association for Bridge and Structural Engineering (IABSE)
Open this publication in new window or tab >>Railway Bridges on the Iron Ore Line in Northern Sweden: From Axle Loads of 14 to 32,5 ton
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2018 (English)In: IABSE Conference Copenhagen 2018: Engineering the Past, to Meet the Needs of the Future, International Association for Bridge and Structural Engineering (IABSE) , 2018, p. 55-62Conference paper, Published paper (Refereed)
Abstract [en]

The Iron Ore Railway Line was built around 1900 and has more than 100 bridges. It has a length of ca 500 km and runs from Kiruna and Malmberget in northern Sweden to the ice-free harbour in Narvik in Norway on the Atlantic and to Luleå in Sweden on the Baltic. The original axle load was 14 ton. The axle load has gradually been increased to 25 ton in 1955, to 30 ton in 1998 and to 32,5 ton in 2017.

The increases in axle loads have been preceded by monitoring and assessment studies of the bridges. The capacity and need for strengthening or replacement of the bridges have been evaluated. Many of the bridges could carry a higher load than what it was designed for. Experiences from studies before the axle load was increased in 1998 and 2017 are presented and discussed.

Place, publisher, year, edition, pages
International Association for Bridge and Structural Engineering (IABSE), 2018
Series
IABSE Symposium Report ; 111
Keywords
Railway bridges, foundations, steel, reinforced and prestressed concrete, Assessment, Strengthening, Fatigue
National Category
Infrastructure Engineering
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-72379 (URN)2-s2.0-85067093793 (Scopus ID)
Conference
IABSE Conference 2018 'Engineering the Past, to Meet the Needs of the Future', 25-27 June, 2018, Copenhagen, Denmark
Note

ISBN för värdpublikation: 978-1-5108-9208-8

Available from: 2018-12-28 Created: 2018-12-28 Last updated: 2021-07-02Bibliographically approved
Persson, M., Ohlsson, U., Silfwerbrand, J. & Emborg, M. (2017). Interface stresses in concrete bridge deck overlays subjected to differentialshrinkage. In: Proceedings of the 23rd Nordic Concrete Research Symposium: . Paper presented at 23th Symposium on Nordic Concrete Research & Developement, Aalborg, Denmark, 21 - 23 August 2017. Oslo, Norway: Nordic Concrete Federation
Open this publication in new window or tab >>Interface stresses in concrete bridge deck overlays subjected to differentialshrinkage
2017 (English)In: Proceedings of the 23rd Nordic Concrete Research Symposium, Oslo, Norway: Nordic Concrete Federation , 2017Conference paper, Published paper (Refereed)
Abstract [en]

Concrete overlays on bridge decks are expected to be more durable as compared with the more common asphalt solution. Besides stresses due to traffic load and temperature variations at service, the overlays are exposed to stresses due to long term shrinkage. Of interest is to evaluate the concrete overlay due to the shrinkage induced stresses at the composite interface. Three strategies have been employed to gain knowledge on the stresses; 1) use of non-destructive test systems via field observations, 2) a numerical study on a concrete composite slab tested in laboratory, 3) recordings of realistic shrinkage and climate data on a reference bridge using vibrating strain gauges and humidity probes in the newly cast concrete overlay. The data were used as input data for a linear elastic finite element model. This article demonstrates this last phase of the work.

Place, publisher, year, edition, pages
Oslo, Norway: Nordic Concrete Federation, 2017
National Category
Infrastructure Engineering
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-65991 (URN)978-82-8208-056-9 (ISBN)
Conference
23th Symposium on Nordic Concrete Research & Developement, Aalborg, Denmark, 21 - 23 August 2017
Available from: 2017-10-06 Created: 2017-10-06 Last updated: 2018-03-27Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0001-5187-2552

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