Change search
Link to record
Permanent link

Direct link
BETA
Publications (10 of 90) Show all publications
Nilimaa, J., Sabau, C., Bagge, N., Puurula, A., Sas, G., Blanksvärd, T., . . . Elfgren, L. (2018). Assessment and Loading to Failure of Three Swedish RC Bridges. In: Eva Lantsoght and Pinar Okumus (Ed.), Evaluation of Concrete Bridge Behavior through Load Testing: International Perspectives (pp. 8.1-8.18). Faarmington Hills, MI: American Concrete Institute, 323, Article ID SP-323-8.
Open this publication in new window or tab >>Assessment and Loading to Failure of Three Swedish RC Bridges
Show others...
2018 (English)In: Evaluation of Concrete Bridge Behavior through Load Testing: International Perspectives / [ed] Eva Lantsoght and Pinar Okumus, Faarmington Hills, MI: American Concrete Institute, 2018, Vol. 323, p. 8.1-8.18, article id SP-323-8Chapter in book (Refereed)
Abstract [en]

Current codes often underestimate the capacity of existing bridges. The purpose of the tests presented here has been to assess the real behaviour and capacity of three types of bridges in order to be able to utilize them in a more efficient way.

The three studied bridges are: (1) Lautajokk – A one-span trough bridge tested in fatigue to check the shear capacity of the section between the slab and the girders; (2) Övik – A two span trough bridge strengthened with Near Surface Mounted Reinforcement (NSMR) of Carbon Fibre Reinforced Polymers (CFRP) tested in bending, shear and torsion; and (3) Kiruna – A five-span prestressed three girder bridge tested to shear-bending failures in the girders and in the slab.

The failure capacities were considerably higher than what the code methods indicated. With calibrated and stepwise refined finite element models, it was possible to capture the real behaviour of the bridges. The experiences and methods may be useful in assessment and better use of other bridges.

Place, publisher, year, edition, pages
Faarmington Hills, MI: American Concrete Institute, 2018
National Category
Infrastructure Engineering
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-69992 (URN)978-1-64195-007-7 (ISBN)
Available from: 2018-06-29 Created: 2018-06-29 Last updated: 2018-08-10Bibliographically approved
Sabau, C., Popescu, C., Sas, G., Blanksvärd, T. & Täljsten, B. (2018). Axially Loaded RC Walls with Cutout Openings Strengthened with FRCM Composites. Journal of composites for construction, 22(6), 04018046-1-04018046-16, Article ID 04018046.
Open this publication in new window or tab >>Axially Loaded RC Walls with Cutout Openings Strengthened with FRCM Composites
Show others...
2018 (English)In: Journal of composites for construction, ISSN 1090-0268, E-ISSN 1943-5614, Vol. 22, no 6, p. 04018046-1-04018046-16, article id 04018046Article in journal (Refereed) Published
Abstract [en]

Upgrading existing buildings to new functional requirements may require new openings that can weaken the structure, promptingthe need for strengthening. In such cases traditional strengthening solutions, such as creating a reinforced concrete (RC) or steel frame aroundthe opening, imply long-term restrictions in the use of the structure compared to solutions that use externally bonded composites. Two fabricreinforcedcementitious matrix (FRCM) composites were used in this study to restore the capacity of panels with newly created doortype openings to that of a solid panel. Five half-scale RC panels acting as two-way action compression members were tested to failure.Two full-field optical deformation measurement systems were used to monitor and analyze the global structural response of each testedpanel (i.e., crack pattern, failure mechanism, and displacement/strain fields). The performance of existing design methods for RC panelshas been assessed in comparison with the experimental results. The capacity of strengthened panels with small openings (450 × 1,050 mm) was entirely restored to that of the solid panel. However, for panels with large openings (900 × 1,050 mm), only 75% of the solid panel’scapacity was restored. The capacity of the strengthened panels was about 175 and 150% higher compared to that of reference panels withsmall and large openings, respectively.

Place, publisher, year, edition, pages
American Society of Civil Engineers (ASCE), 2018
Keywords
FRCM, Reinforced concrete, Walls with openings, Digital image correlation
National Category
Infrastructure Engineering Building Technologies
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-70579 (URN)10.1061/(ASCE)CC.1943-5614.0000867 (DOI)000447252600001 ()2-s2.0-85051927413 (Scopus ID)
Note

Validerad;2018;Nivå 2;2018-08-24 (andbra)

Available from: 2018-08-24 Created: 2018-08-24 Last updated: 2018-10-29Bibliographically approved
Huang, Z., Lu, Z., Song, S., Tu, Y., Blanksvärd, T., Sas, G. & Elfgren, L. (2018). Finite element analysis of shear deformation in reinforced concrete shear-critical beams. Structure and Infrastructure Engineering, 14(6), 791-806
Open this publication in new window or tab >>Finite element analysis of shear deformation in reinforced concrete shear-critical beams
Show others...
2018 (English)In: Structure and Infrastructure Engineering, ISSN 1573-2479, E-ISSN 1744-8980, Vol. 14, no 6, p. 791-806Article in journal (Refereed) Published
Abstract [en]

The objective of this paper was to study the contribution of shear deformation in reinforced concrete (RC) shear-critical beams. A 2D concrete material model based on smeared fixed crack was presented and incorporated into a commercial finite element (FE) software. A method of calculating shear and flexure deformation separately out of total deformation in the shear span was presented and implemented into the FE analysis. Several experiments of RC shear-critical beams were simulated and good agreement between the experimental and numerical results was obtained in terms of total deformation, flexure deformation, shear deformation and crack patterns. The results show that after shear cracking, the contribution of shear deformation to total deformation increases rapidly. The shear span-to-depth ratio, the longitudinal reinforcement, the shear reinforcement and the load level could be the critical factor to influence the contribution of shear deformation. It appears that for RC shear-critical beams without shear reinforcement, the deformational behaviour is governed by flexure deformation. However, for RC beams with shear reinforcement, the contribution of shear deformation is not negligible after shear cracks develop. Moreover, the measuring method could also affect the measured shear deformation. Finally, future work on experimental investigation into this topic is recommended.

Place, publisher, year, edition, pages
Taylor & Francis, 2018
National Category
Infrastructure Engineering
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-65169 (URN)10.1080/15732479.2017.1360915 (DOI)000429038000009 ()
Note

Validerad;2018;Nivå 2;2018-04-10 (andbra)

Available from: 2017-08-17 Created: 2017-08-17 Last updated: 2018-04-19Bibliographically approved
Sabau, C., Popescu, C., Bagge, N., Sas, G., Blanksvärd, T. & Täljsten, B. (2018). Local and global behavior of walls with cut-out openings in multi-story reinforced concrete buildings. Engineering structures
Open this publication in new window or tab >>Local and global behavior of walls with cut-out openings in multi-story reinforced concrete buildings
Show others...
2018 (English)In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323Article in journal (Refereed) Submitted
Abstract [en]

This paper presents the finite element analysis (FEA) results of a multi-story reinforced concrete (RC) building having precast and cast-in-place load bearing walls. Door-type cut-out openings (height: 2.1 m, width: 0.9–4.4 m) were created at the first and second story of the building. Results from experimental tests on axially loaded RC panels were used to verify the modeling approach. The influence of cut-out openings on the response of individual RC panels, failure modes, and load redistribution to adjacent members was analyzed. Moreover, the wall bearing capacities obtained from FEA were compared with the values calculated from design equations. The results revealed that the robustness of multi-story buildings having RC load bearing wall systems decrease considerably with the creation of cut-out openings. However, owing to the initial robustness of the buildings, large cut-outopenings could be created under normal service conditions without strengthening of the building structure. Furthermore, design equations provided very conservative predictions of the ultimate capacity characterizing the solid walls and walls with small openings, whereas similar FEA and analytically predicted capacities were obtained for walls with large openings.

Keywords
FEM, reinforced concrete, building assessment, wall, openings
National Category
Building Technologies
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-70883 (URN)
Available from: 2018-09-18 Created: 2018-09-18 Last updated: 2018-11-23
Sabau, C., Popescu, C., Sas, G., Schmidt, J. W., Blanksvärd, T. & Täljsten, B. (2018). Strengthening of RC beams using bottom and side NSM reinforcement. Composites Part B: Engineering, 149, 82-91
Open this publication in new window or tab >>Strengthening of RC beams using bottom and side NSM reinforcement
Show others...
2018 (English)In: Composites Part B: Engineering, ISSN 1359-8368, E-ISSN 1879-1069, Vol. 149, p. 82-91Article in journal (Refereed) Published
Abstract [en]

The allowable strain in fibre reinforced polymers reinforcement is limited by design codes to avoid debonding. The near-surface mounted (NSM) reinforcement technique has been proven to produce better anchorage behaviour compared to externally bonded reinforcement solutions. However, NSM solutions do not always eliminate debonding issues, with concrete cover detachment (CCD) typically occurring in RC beams strengthened for flexure. This experimental study investigated the efficiency of side mounted (S) compared to bottom mounted (B) NSM bars to prevent CCD. The experimental results were compared to models available in the literature that predict the observed failure modes and the crack spacing in the NSM anchorage zone. Compared to B-NSM, the S-NSM solution was successful in avoiding brittle CCD failure and showed increased rotational capacity and energy dissipation at failure. Existing CCD debonding models were found to be conservative.

Place, publisher, year, edition, pages
Elsevier, 2018
National Category
Infrastructure Engineering
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-68708 (URN)10.1016/j.compositesb.2018.05.011 (DOI)000442979500010 ()2-s2.0-85047119715 (Scopus ID)
Note

Validerad;2018;Nivå 2;2018-06-01 (svasva)

Available from: 2018-05-14 Created: 2018-05-14 Last updated: 2018-09-10Bibliographically approved
Bagge, N., Nilimaa, J., Blanksvärd, T., Täljsten, B., Elfgren, L., Sundquist, H. & Carolin, A. (2017). Assessment and failure test of a prestressed concrete bridge. In: Jaap Bakker; Dan M Frangopol; Klaas van Breugel (Ed.), Life-Cycle of Engineering Systems: Emphasis on Sustainable Civil Infrastructure. Paper presented at 5th International Symposium on Life-Cycle Engineering, IALCCE 2016, Delft, Netherlands, 16-20 October 2016 (pp. 1058-1063). Leiden: CRC Press/Balkema
Open this publication in new window or tab >>Assessment and failure test of a prestressed concrete bridge
Show others...
2017 (English)In: Life-Cycle of Engineering Systems: Emphasis on Sustainable Civil Infrastructure / [ed] Jaap Bakker; Dan M Frangopol; Klaas van Breugel, Leiden: CRC Press/Balkema , 2017, p. 1058-1063Conference paper, Published paper (Refereed)
Abstract [en]

Tests have been carried out at service- and ultimate load levels of a 55 year-old prestressed concrete girder bridge. The bridge, located in Kiruna, Sweden, was continuous in five spans with a total length of 121.5 m. The overall aim of the study was to determinate the accuracy of assessment methods for existing structures and to provide procedures for optimized assessment. Before the tests a 2D finite element (FE) analysis was performed to predict the behavior and load-carrying capacity of the bridge. In order to more accurately assess the bridge response a 3D FE model has now been developed. The actual loading history and material properties has been considered in the model. A Life Cycle Cost Assessment of the bridge has also been performed

Place, publisher, year, edition, pages
Leiden: CRC Press/Balkema, 2017
National Category
Infrastructure Engineering
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-63448 (URN)2-s2.0-85018632781 (Scopus ID)9781138028470 (ISBN)
Conference
5th International Symposium on Life-Cycle Engineering, IALCCE 2016, Delft, Netherlands, 16-20 October 2016
Available from: 2017-05-19 Created: 2017-05-19 Last updated: 2018-03-26Bibliographically approved
Häggström, J., Blanksvärd, T. & Täljsten, B. (2017). Bridge over Åby River: Evaluation of full scale testing.
Open this publication in new window or tab >>Bridge over Åby River: Evaluation of full scale testing
2017 (English)Report (Other academic)
Alternative title[sv]
Bro över Åby älv : Utvärding av fullskaleförsök
Publisher
p. 131
Series
Technical report / Luleå University of Technology, ISSN 1402-1536
Keywords
Full-scale monitoring steel truss bridge
National Category
Infrastructure Engineering
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-61614 (URN)978-91-7583-823-6 (ISBN)
Available from: 2017-01-24 Created: 2017-01-24 Last updated: 2018-03-20Bibliographically approved
Popescu, C., Sas, G., Blanksvärd, T. & Täljsten, B. (2017). Concrete walls with cutout openings strengthened by FRP confinement (ed.). Journal of composites for construction, 21(3), Article ID 04016106.
Open this publication in new window or tab >>Concrete walls with cutout openings strengthened by FRP confinement
2017 (English)In: Journal of composites for construction, ISSN 1090-0268, E-ISSN 1943-5614, Vol. 21, no 3, article id 04016106Article in journal (Refereed) Published
Abstract [en]

Redesigning buildings to improve their space efficiency and allow changes in use is often essential during their service lives tocomply with shifts in living standards and functional demands. This may require the introduction of new openings in elements such as beams,walls, and slabs, which inevitably reduces their structural performance and hence requires repair or strengthening. However, there are uncertaintiesregarding both the effects of openings and the best remedial options for them. Here, the authors report on an experimental investigation ofthe effectiveness of fiber-reinforced polymer (FRP)–based strengthening for restoring the axial capacity of a solid RC wall after cutting openings.Nine half-scale specimens, designed to represent typical wall panels in residential buildings with and without door-type openings, were testedto failure. It was found that FRP-confinement and mechanical anchorages increased the axial capacity of walls with small and large openings(which had 25 and 50% reductions in cross-sectional area, respectively) by 34–50% and 13–27%, to 85–94.8% and 56.5–63.4% of their precuttingcapacity, respectively. 

Place, publisher, year, edition, pages
American Society of Civil Engineers (ASCE), 2017
National Category
Infrastructure Engineering
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-2760 (URN)10.1061/(ASCE)CC.1943-5614.0000759 (DOI)000400524800008 ()2-s2.0-85017517559 (Scopus ID)071b8226-9b6c-41f9-9efc-499979742502 (Local ID)071b8226-9b6c-41f9-9efc-499979742502 (Archive number)071b8226-9b6c-41f9-9efc-499979742502 (OAI)
Note

Validerad; 2017; Nivå 2; 2017-04-25 (andbra)

 

Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-11-20Bibliographically approved
Sabau, C., Popescu, C., Sas, G., Blanksvärd, T. & Täljsten, B. (2017). Concrete Walls with Openings Strengthened Using FRCM Composites. In: Maurizio Guadagnini & Sue Keighley (Ed.), Advanced Composites in Construction: Conference Proceedings. Paper presented at 8th Biennial Conference on Advanced Composites In Construction, Sheffield, 5-7 September 2017 (pp. 188-192). Chesterfield: NetComposites Limited
Open this publication in new window or tab >>Concrete Walls with Openings Strengthened Using FRCM Composites
Show others...
2017 (English)In: Advanced Composites in Construction: Conference Proceedings / [ed] Maurizio Guadagnini & Sue Keighley, Chesterfield: NetComposites Limited , 2017, p. 188-192Conference paper, Published paper (Refereed)
Abstract [en]

In the current social and economic context, upgrading or retrofitting of existing buildings, instead of replacingwith new constructions, is becoming more and more popular due to shorter service interruptions,accessibility, and economic reasons. Upgrading building to current living standards and new functionalityneed often require new openings to be created in structural elements such as reinforced concrete walls andslabs. With the aim of improving existing strengthening solutions for such cases, this study presents someaspects of an experimental investigation of the effectiveness of fibre reinforced cementitious matrixcomposites (FRCM) strengthening for restoring the axial capacity of a solid reinforced concrete wall aftercreating new door openings. Five half-scale specimens, designed to represent typical wall panels inresidential buildings with and without door-type openings, were tested to failure. It was found that FRCMsystems were able to fully restore the axial capacity of the walls with small openings to that of the solid wall,and to restore the axial capacity of walls with large openings to approximately 75% of that of the solid wall.

Place, publisher, year, edition, pages
Chesterfield: NetComposites Limited, 2017
National Category
Building Technologies Infrastructure Engineering
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-66500 (URN)2-s2.0-85040222976 (Scopus ID)
Conference
8th Biennial Conference on Advanced Composites In Construction, Sheffield, 5-7 September 2017
Available from: 2017-11-08 Created: 2017-11-08 Last updated: 2018-03-28Bibliographically approved
Häggström, J., Blanksvärd, T., Collin, P. & Tu, Y. (2017). Full-scale testing to failure of a steel truss railway bridge. Proceedings of the Institution of Civil Engineers: Engineering Sustainability, 170(2), 93-101
Open this publication in new window or tab >>Full-scale testing to failure of a steel truss railway bridge
2017 (English)In: Proceedings of the Institution of Civil Engineers: Engineering Sustainability, ISSN 1478-4637, E-ISSN 1751-7664, Vol. 170, no 2, p. 93-101Article in journal (Refereed) Published
Abstract [en]

Significant resources have been invested in maintaining existing infrastructure. Many structures are becoming old, do not meet current requirements, or are reaching the end of their life cycle. It is not feasible or sustainable to replace all of those that may be deemed obsolete; however, often their specified capacities are very conservative. So there is an urgent need to obtain more robust knowledge of their true status. This paper describes a unique project, in which a 33 m long steel truss railway bridge (over the Åby River) was tested to failure. The findings can be used to identify optimal solutions for other bridges of the same design that are still in use, notably the bridge over Rautasjokk (a river in Sweden). These two bridges were tested in three stages. This paper focuses on the second stage, wherein Åby Bridge was subjected to static full-scale testing to failure, by pulling it downwards. The global failure mode consisted of buckling of the top chord with yielding of the steel starting at a total load of 8 MN and the peak load being reached at around 11 MN, corresponding to a load approximately four to five times higher than the characteristic design load.

Place, publisher, year, edition, pages
Institution of Civil Engineers, 2017
Keywords
bridges field testing & monitoring steel structures
National Category
Infrastructure Engineering
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-62708 (URN)10.1680/jbren.15.00025 (DOI)000405988000002 ()
Note

Validerad;2017;Nivå 2;2017-06-07 (rokbeg)

Available from: 2017-03-27 Created: 2017-03-27 Last updated: 2018-12-14Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-5154-7044

Search in DiVA

Show all publications