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FRCM-Composites for Strengthening Concrete Walls with Openings: Experimental and Numerical Analysis
Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.ORCID iD: 0000-0003-1329-555x
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 [en]
FRCM, reinforced concrete, walls, openings, strenghtening
National Category
Building Technologies Infrastructure Engineering
Research subject
Structural Engineering
Identifiers
URN: urn:nbn:se:ltu:diva-70886ISBN: 978-91-7790-205-8 (print)ISBN: 978-91-7790-206-5 (electronic)OAI: oai:DiVA.org:ltu-70886DiVA, id: diva2:1249211
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: 2018-11-21Bibliographically approved
List of papers
1. Review of FRCM strengthening solutions for structural wall panels
Open this publication in new window or tab >>Review of FRCM strengthening solutions for structural wall panels
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(English)In: American Concrete Institute. Publication SP, ISSN 0193-2527, E-ISSN 1094-8120Article in journal (Refereed) In press
Abstract [en]

This paper summarizes the state-of-the-art on the topic of structural wall panels strengthened using fabric reinforced cementitious matrix composites (FRCM) composites. A systematic review of the literature is carried out to identify gaps in the available literature. A database of experimental tests, relevant for structural panels, was created and used to assess the influence of parameters such as test method, fiber type and material compressive strength, on the performance of FRCM strengthening. Since experimental investigations on walls strengthened with FRCM composites is still limited and mostly focused on shear, further investigations on walls as compression members can be considered timely, especially walls with openings, which have been overlooked. Experimental tests performed by the authors on reinforced concrete walls with openings are presented and assessed relative to the complete database. It was shown that FRCM composites are suitable repair solutions when new openings need to be created in existing walls.

Keywords
FRCM, reinforced concrete, structural walls
National Category
Building Technologies
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-70880 (URN)
Funder
SBUF - Sveriges Byggindustriers Utvecklingsfond, 13246EU, FP7, Seventh Framework Programme, MC-ITN-2013-607851
Available from: 2018-09-18 Created: 2018-09-18 Last updated: 2018-11-23
2. Influence of the fiber type and matrix age of the bonding of FRCM composite strips applied to concrete substrates
Open this publication in new window or tab >>Influence of the fiber type and matrix age of the bonding of FRCM composite strips applied to concrete substrates
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2016 (English)In: Eighth International Conference on Fibre-Reinforced Polymer (FRP) Composites in Civil Engineering / [ed] J.G. Teng and J.G. Dai, 2016, p. 456-461Conference paper, Published paper (Refereed)
Abstract [en]

Fiber reinforced cementitious matrix (FRCM) composites represent an alternative to fiber reinforced polymer(FRP) composites for strengthening existing civil structures. FRCM is comprised of fibers, usually in the form ofa textile with an open-mesh configuration, embedded in an inorganic mortar matrix. It shares the advantages ofFRP systems and overcomes some of its drawbacks, which makes it suitable for a wide range of applications.Although research on this topic is still scarce, it has been shown that debonding represents a key factor in itsperformance. In order to gain more insight in this issue, a series of classical push-pull single-lap direct shear testswere carried out on basalt, carbon, and glass FRCM-concrete joints. The results allow for comparing theperformance of the joints with carbon, basalt, and glass fibers in terms of applied load – global slip response andfailure mode. The influence of matrix age was also investigated. The curing time of the mortar matrix was foundto influence the load carrying capacity of carbon FRCM – concrete joints.

Keywords
FRCM, basalt, carbon, glass, concrete, debonding.
National Category
Composite Science and Engineering Infrastructure Engineering
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-62570 (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: 2018-09-18Bibliographically approved
3. Use of image correlation system to study the bond behavior of FRCM-concrete joints
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
4. Effect of cut-out openings on the axial strength of concrete walls
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
5. Local and global behavior of walls with cut-out openings in multi-story reinforced concrete buildings
Open this publication in new window or tab >>Local and global behavior of walls with cut-out openings in multi-story reinforced concrete buildings
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2019 (English)In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 187, p. 57-72Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
FEM, reinforced concrete, building assessment, wall, openings
National Category
Building Technologies Other Civil Engineering
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-70883 (URN)10.1016/j.engstruct.2019.02.046 (DOI)000462689900006 ()2-s2.0-85062088838 (Scopus ID)
Note

Validerad;2019;Nivå 2;2019-03-07 (inah)

Available from: 2018-09-18 Created: 2018-09-18 Last updated: 2019-04-23Bibliographically approved
6. Axially Loaded RC Walls with Cutout Openings Strengthened with FRCM Composites
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

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