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Publications (10 of 16) 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
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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
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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
Sabau, C. (2018). FRCM-Composites for Strengthening Concrete Walls with Openings: Experimental and Numerical Analysis. (Doctoral dissertation). Luleå: Luleå University of Technology
Open this publication in new window or tab >>FRCM-Composites for Strengthening Concrete Walls with Openings: Experimental and Numerical Analysis
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Upgrading existing buildings to new functional requirements may require new openings that can weaken the structure, prompting the need for strengthening. In such cases, traditional strengthening solutions, such as creating a reinforced concrete or steel frame around the opening, imply long-term restrictions in the use of the structure.

In this study, the author carries experimental and numerical investigations on fiber reinforced cementitious matrix (FRCM) composites and their effectiveness for strengthening reinforced concrete walls with openings.

To assess the performance of FRCM composite having different fiber types and their suitability for strengthening reinforce concrete walls with openings, single-lap direct shear tests were carried out using carbon, glass, and basalt FRCM-concrete joints. A novel non-contact measurement approach, based on digital image photogrammetry, applied to the experimental study of the bond behavior of FRCM composites was proposed and investigated. The proposed measurement approach showed higher spatial measurement resolution and increased accuracy compared to traditional contact approaches.

The effect of cutout openings on the structural behavior of concrete walls was investigated experimentally, by loading to failure, half-scale, precast reinforced concrete panels with and without openings. The tested specimens were two-way action panels to which axial load with a small eccentricity was applied, thus the tested panels were representative of wall panels in buildings. The effect of cutout openings on the global behavior of a building structure was investigated through finite element analysis of an existing building where cutout openings were introduced in wall panels. Depending on their size, cutout openings can significantly decrease the capacity of the wall. The effectiveness of FRCM strengthening to restore the capacity walls with cutout openings was investigated experimentally. FRCM strengthening increased the capacity of walls having small door type openings (opening width was 25% of the wall’s width) to that of the solid wall. The capacity of the walls with large cutout openings was (opening width was 50% of the wall’s width) was increased to 75% of the solid wall’s capacity. The numerical and experimental analysis indicated that the decrease in axial load caused by cutout openings was proportional to the width opening. However, the numerical analysis of buildings structure indicated that the effects of openings on the buildings load carrying capacity are less severe.

Place, publisher, year, edition, pages
Luleå: Luleå University of Technology, 2018
Series
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
Keywords
FRCM, reinforced concrete, walls, openings, strenghtening
National Category
Building Technologies Infrastructure Engineering
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-70886 (URN)978-91-7790-205-8 (ISBN)978-91-7790-206-5 (ISBN)
Public defence
2018-11-14, F1031, Luleå University of Technology, Luleå, 09:00 (English)
Opponent
Supervisors
Available from: 2018-09-25 Created: 2018-09-18 Last updated: 2018-10-24Bibliographically approved
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
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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
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
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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
Gonzalez-Libreros, J., Sabau, C., Sneed, L. H., Sas, G. & Pellegrino, C. (2017). Effect of Confinement with FRCM Composites on Damaged Concrete Cylinders. In: Mechtcherine, Viktor; Slowik, Volker; Kabele, Petr (Ed.), Strain-Hardening Cement-Based Composites: Shcc4. Paper presented at International Conference on Strain-Hardening Cement-Based Composites, SHCC 2017, Dresden, Germany, 18-20 September 2017 (pp. 770-777). Dordrecht: Springer
Open this publication in new window or tab >>Effect of Confinement with FRCM Composites on Damaged Concrete Cylinders
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2017 (English)In: Strain-Hardening Cement-Based Composites: Shcc4 / [ed] Mechtcherine, Viktor; Slowik, Volker; Kabele, Petr, Dordrecht: Springer, 2017, p. 770-777Conference paper, Published paper (Refereed)
Abstract [en]

Confinement of axially loaded concrete members in existing structures is required when a change in use is expected or when there is a need to upgrade the structure to meet current design standards. In addition, after unusual overloading events (e.g., earthquakes), axially loaded members can suffer damage that increases the need of their retrofitting by means of confinement. The study of fiber reinforced cementitious matrix (FRCM) composites for confinement of compression members has gained attention in recent years due to the capability to overcome some of the disadvantages associated with more traditional strengthening techniques. However, the available experimental evidence is still scarce, and research on the topic is necessary. In this paper, the results of an experimental campaign performed on concrete cylinders confined with FRCM jackets are presented. Before strengthening, some specimens were preloaded in order to achieve specified damage levels. The specimens were then subjected to uniaxial concentric compressive loading. The axial load and axial strain response was recorded for each specimen. In addition, the elastic modulus of confined and unconfined specimens was determined. Results show that confinement with FRCM composites is able to provide an increase in the axial capacity of undamaged and damaged concrete cylinders.

Place, publisher, year, edition, pages
Dordrecht: Springer, 2017
Series
RILEM Bookseries, ISSN 2211-0844 ; 15
National Category
Infrastructure Engineering
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-65594 (URN)10.1007/978-94-024-1194-2_88 (DOI)2-s2.0-85029409587 (Scopus ID)978-94-024-1193-5 (ISBN)978-94-024-1194-2 (ISBN)
Conference
International Conference on Strain-Hardening Cement-Based Composites, SHCC 2017, Dresden, Germany, 18-20 September 2017
Available from: 2017-09-12 Created: 2017-09-12 Last updated: 2018-03-28Bibliographically approved
Gonzalez-Libreros, J., Sabau, C., Sneed, L., Pellegrino, C. & Sas, G. (2017). State of research on shear strengthening of RC beams with FRCM composites. Construction and Building Materials, 149, 444-458
Open this publication in new window or tab >>State of research on shear strengthening of RC beams with FRCM composites
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2017 (English)In: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 149, p. 444-458Article in journal (Refereed) Published
Abstract [en]

This paper summarizes the state of research on the topic of shear strengthening of RC beams using externally bonded FRCM composites. In the first part of this paper, a detailed bibliographical review of the literature on the shear strengthening of RC beams using FRCM composites is carried out, and a database of experimental tests is developed. Analysis of the database shows that FRCM composites are able to increase the shear strength of RC beams. The effectiveness of the strengthening system appears to be influenced by parameters including the wrapping configuration, matrix compressive strength relative to the concrete compressive strength, and axial rigidity of the fibers. Different failure modes have been reported, including fracture of the fibers, detachment of the FRCM jacket (with or without concrete attached), and slippage of the fibers through the mortar. A possible interaction between the internal transverse steel reinforcement and the FRCM system has also been observed. In the second part of this paper, four design models proposed to predict the contribution of the FRCM composite to the shear strength of RC beams are assessed using the database developed. Results show that the use of the properties of the FRCM composite in Models 3 and 4 instead of the fiber mechanical characteristics does not significantly increase the accuracy of the models. A simple formulation such as that proposed by Model 1, based on the bare fiber properties, is found to be more accurate for beams with or without composite detachment.

Place, publisher, year, edition, pages
Elsevier, 2017
National Category
Infrastructure Engineering
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-63574 (URN)10.1016/j.conbuildmat.2017.05.128 (DOI)000405536800041 ()2-s2.0-85019931416 (Scopus ID)
Note

Validerad;2017;Nivå 2;2017-05-29 (andbra)

Available from: 2017-05-29 Created: 2017-05-29 Last updated: 2018-07-10Bibliographically approved
Sabau, C., Gonzalez-Libreros, J., Sneed, L., Sas, G., Pellegrino, C. & Täljsten, B. (2017). Use of image correlation system to study the bond behavior of FRCM-concrete joints. Materials and Structures, 50(3), Article ID 172.
Open this publication in new window or tab >>Use of image correlation system to study the bond behavior of FRCM-concrete joints
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2017 (English)In: Materials and Structures, ISSN 1359-5997, E-ISSN 1871-6873, Vol. 50, no 3, article id 172Article in journal (Refereed) Published
Abstract [en]

This paper presents a non-contact measurement approach, based on digital photogrammetry,applied to the experimental study of the bond behavior of fiber reinforced cementitious matrixcomposite (FRCM) - concrete joints tested in single-lap direct shear tests. The use of digitalphotogrammetry techniques and traditional contact measurement approaches for determiningdisplacement and strain are investigated and compared. The results show that measurements ofstrain in the fiber bundles determined using the image correlation system (ICS) correlate well withthose obtained from electrical strain gauges. However, differences of 38% to 52% were observedbetween the maximum strain measured with either ICS or electrical strain gages attached to thefiber bundles and the maximum strain in the fiber bundles computed from the maximum appliedload. ICS is also used to measure slip and strain of bare fiber bundles, and results show that theload distribution among fiber bundles is non-uniform. The proposed measurement approach showshigher spatial measurement resolution and increased accuracy compared to traditional contactapproaches by enabling measurements in each fiber bundle and overcoming the need to attachadditional elements to the tested specimen.

Place, publisher, year, edition, pages
Springer, 2017
Keywords
bond, carbon fiber, digital image correlation, direct shear, FRCM composite, point tracking
National Category
Composite Science and Engineering Infrastructure Engineering
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-62574 (URN)10.1617/s11527-017-1036-4 (DOI)000404147000003 ()2-s2.0-85018506006 (Scopus ID)
Projects
European Network for Durable Reinforcement and Rehabilitation Solutions (endure)
Funder
EU, FP7, Seventh Framework Programme, MC-ITN-2013-607851
Note

Validerad; 2017; Nivå 2; 2017-04-26 (andbra)

Available from: 2017-03-20 Created: 2017-03-20 Last updated: 2018-09-18Bibliographically approved
Popescu, C., Sas, G., Sabau, C. & Blanksvärd, T. (2016). Effect of cut-out openings on the axial strength of concrete walls (ed.). Journal of Structural Engineering, 142(11), Article ID 4016100.
Open this publication in new window or tab >>Effect of cut-out openings on the axial strength of concrete walls
2016 (English)In: Journal of Structural Engineering, ISSN 0733-9445, E-ISSN 1943-541X, Vol. 142, no 11, article id 4016100Article in journal (Refereed) Published
Abstract [en]

Old structures are frequently modified to comply with current living standards and/or legislation. Such modifications may include the addition of new windows or doors and paths for ventilation and heating systems, all of which require openings to be cut into structural walls. However, effects of the required openings are not sufficiently understood. Thus, the objective of the work reported here was to analyze openings’ effects on the axial strength of large concrete wall panels. Three half-scaled walls with two opening configurations, corresponding to “small” and “large” door openings, were subjected to a uniformly distributed axial load with a small eccentricity. The results indicate that the 25% and 50% reductions in cross-sectional area of the solid wall caused by introducing the small and large openings reduced the load-carrying capacity by nearly 36% and 50%, respectively. The failure progression was captured using digital image correlation technique and the results indicated involvement of a plate mechanism rather than uniaxial behavior as adopted in current design codes. Using a simplified procedure, the load-carrying capacity was predicted using existing design models found in the research literature and design codes.

National Category
Infrastructure Engineering
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-13543 (URN)10.1061/(ASCE)ST.1943-541X.0001558 (DOI)000386366600008 ()2-s2.0-84991677088 (Scopus ID)cc593011-a98a-471f-9ff8-ca86152f99d9 (Local ID)cc593011-a98a-471f-9ff8-ca86152f99d9 (Archive number)cc593011-a98a-471f-9ff8-ca86152f99d9 (OAI)
Note

Validerad; 2016; Nivå 2; 2016-11-08 (andbra)

Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-09-18Bibliographically approved
Gonzalez-Libreros, J., Sabau, C., Sneed, L., Pellegrino, C. & Sas, G. (2016). Experimental investigation on RC beams strenghened in shear with  externally bonded composites. In: J.G. Teng and J.G. Dai (Ed.), Eighth International Conference onFibre-Reinforced Polymer (FRP) Composites in Civil Engineering: . Paper presented at 8th International Conference on Fibre-Reinforced Polymer (FRP) Composites in Civil Engineering, Hong Kong, China 14-16 December 2016 (pp. 384-389). Hong Kong, China: The Hong Kong Polytechnic University
Open this publication in new window or tab >>Experimental investigation on RC beams strenghened in shear with  externally bonded composites
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2016 (English)In: Eighth International Conference onFibre-Reinforced Polymer (FRP) Composites in Civil Engineering / [ed] J.G. Teng and J.G. Dai, Hong Kong, China: The Hong Kong Polytechnic University , 2016, p. 384-389Conference paper, Published paper (Refereed)
Abstract [en]

This paper presents the results of an experimental campaign carried out to investigate the behavior of reinforcedconcrete (RC) beams strengthened in shear using externally bonded advanced composite materials. In order tocompare their performance, two different types of composite materials were used to strengthen the beams: fiberreinforced polymer (FRP) and fiber reinforced cementitious matrix (FRCM) composites. The beams were thentested in four-point bending scheme, and measurements regarding applied load and mid-span displacements wereacquired. Observations regarding the gain in shear strength, influence on mid-span deflection and ductility, andcomparison of the performance of the two strengthening systems are provided. For specimens strengthened withFRCM composite, the contribution to the shear strength provided by the FRCM strengthening system is comparedwith the value predicted by an analytical model found in the available literature.

Place, publisher, year, edition, pages
Hong Kong, China: The Hong Kong Polytechnic University, 2016
Keywords
FRP, FRCM, reinforced concrete, shear, strengthening
National Category
Building Technologies
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-62572 (URN)
Conference
8th International Conference on Fibre-Reinforced Polymer (FRP) Composites in Civil Engineering, Hong Kong, China 14-16 December 2016
Funder
EU, FP7, Seventh Framework Programme, MC-ITN-2013-607851
Available from: 2017-03-20 Created: 2017-03-20 Last updated: 2018-03-28Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-1329-555x

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