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Mahal, Mohammed
Publications (8 of 8) Show all publications
Mahal, M., Blanksvärd, T. & Täljsten, B. (2016). A two-scale damage model for high-cycle fatigue at the fiber-reinforced polymer-concrete interface (ed.). Computers and Concrete, 116, 12-20
Open this publication in new window or tab >>A two-scale damage model for high-cycle fatigue at the fiber-reinforced polymer-concrete interface
2016 (English)In: Computers and Concrete, ISSN 1598-8198, Vol. 116, p. 12-20Article in journal (Refereed) Published
Abstract [en]

This paper presents a new two-scale damage model of the fiber-reinforced polymer (FRP)-concrete bond under high-cycle fatigue. The material behavior is modeled as elastic-plastic coupled with damage for the microscale analysis and as elastic for the mesoscale analysis. A new damage law for the interface joint is described. The two-scale damage model has been implemented as a material model for a three dimensional an eight-node interface element of zero thickness and used to simulate a double shear joint specimen under high cycle fatigue. The numerical calculations were performed with a full incremental cycle solution and a new cycle jump approach. Comparing the results from the finite element method (FEM) model with experimental data shows that the model is capable of accurately predicting the cyclic fatigue loading slip response of the joint interface.

National Category
Infrastructure Engineering
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-4720 (URN)10.1016/j.finel.2016.03.003 (DOI)000375933400002 ()2-s2.0-84964342113 (Scopus ID)2b565140-f4cb-4fb0-b6b0-3732d2b1fcfb (Local ID)2b565140-f4cb-4fb0-b6b0-3732d2b1fcfb (Archive number)2b565140-f4cb-4fb0-b6b0-3732d2b1fcfb (OAI)
Note
Validerad; 2016; Nivå 2; 20150114 (mohsal)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Mahal, M. (2016). Experimental investigation of RC beams strengthened with FRP materials under monotonic and fatigue loads (ed.).
Open this publication in new window or tab >>Experimental investigation of RC beams strengthened with FRP materials under monotonic and fatigue loads
2016 (English)Report (Other academic)
Abstract [en]

Carbon fiber-reinforced polymers are becoming more widely used for repair and strengthening of reinforced concrete bridge members by using two main common methods , externally bonded (EBR) to the tension surface of the member or internally located in a near surface mounted location (NSM).The selection of the efficient method from these methods under fatigue load is uncertain.This report presents the results from a laboratory test of a reinforced concrete beams under monotonic and fatigue loads, flexural strengthened by two strengthened system as EBR (externally bonded ) reinforcement and NSM (Near Surface Mounted) reinforcement, at Luleå University of Technology. The influence of strengthening material properties and the case where the concrete was pre-cracked are investigated and discussed through analysing the failure mechanism, load-deflection, and strain measurements in steel bars and CFRP. This study should improve our understanding the behavior of the strengthened reinforced concrete beam in two main strengthening methods under fatigue loading conditions, and should guide us to identify the advantages and disadvantages of these methods.

Publisher
p. 150
National Category
Construction Management
Research subject
Construction Engineering and Management
Identifiers
urn:nbn:se:ltu:diva-23137 (URN)5b976adc-4dc7-48fa-bad7-6d9107fdd628 (Local ID)5b976adc-4dc7-48fa-bad7-6d9107fdd628 (Archive number)5b976adc-4dc7-48fa-bad7-6d9107fdd628 (OAI)
Note

Upprättat; 2015; 20150114 (mohsal)

Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2017-11-24Bibliographically approved
Mahal, M., Täljsten, B. & Blanksvärd, T. (2016). Experimental performance of RC beams strengthened with FRP materials under monotonic and fatigue loads (ed.). Construction and Building Materials, 122, 126-139
Open this publication in new window or tab >>Experimental performance of RC beams strengthened with FRP materials under monotonic and fatigue loads
2016 (English)In: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 122, p. 126-139Article in journal (Refereed) Published
Abstract [en]

Carbon fiber-reinforced polymers (CFRPs) are increasingly being used to repair and strengthen reinforced concrete (RC) bridge members. CFRP strengthening may be applied by bonding polymeric plates to the exterior of the member’s tension surface or by placing CFRP bars inside the concrete member cover to provide near-surface mounted reinforcement. It is not clear which of these approaches is most effective at resisting fatigue loads. To compare their efficacy, four-point bending tests with reinforced concrete beams were conducted under monotonic and fatigue loading using both strengthened and unstrengthened RC beams having steel reinforcements with identical stress levels. The influence of the strengthening material’s properties and prior cracking of the member are investigated and discussed by analyzing failure mechanisms, load-deflection curves, and strain measurements for steel bars and CFRP materials observed during loading experiments. The results obtained indicate that the efficiency of strengthening is primarily determined by the relief of local stress in the member’s reinforcing steel bars before they rupture, and the fatigue life of the reinforcing steel after its initial fracturing. The latter of these quantities is related to the strengthened member’s ability to absorb the energy released at the moment the reinforcing bar fractures.

Keywords
Fiber-reinforced polymer, Reinforced concrete, Beam, Fatigue test
National Category
Infrastructure Engineering
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-15173 (URN)10.1016/j.conbuildmat.2016.06.060 (DOI)000382340600014 ()2-s2.0-84976293850 (Scopus ID)ea959f68-1358-4e72-bf6a-492e00df3d94 (Local ID)ea959f68-1358-4e72-bf6a-492e00df3d94 (Archive number)ea959f68-1358-4e72-bf6a-492e00df3d94 (OAI)
Note

Validerad; 2016; Nivå 2; 20150114 (mohsal)

Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2022-07-05Bibliographically approved
Mahal, M., Täljsten, B. & Blanksvärd, T. (2016). Fatigue analysis of RC beams strengthened in flexure using CFRP (ed.). Composite structures
Open this publication in new window or tab >>Fatigue analysis of RC beams strengthened in flexure using CFRP
2016 (English)In: Composite structures, ISSN 0263-8223, E-ISSN 1879-1085Article in journal (Refereed) Submitted
Abstract [en]

The increasing use of Fiber Reinforced Polymers (FRP) to repair, strengthen or upgrade reinforced concrete (RC) structural elements means that there is a need to develop analytical methods for analyzing the behavior of strengthened members under fatigue loading. This paper describes an analytical model for simulating the fatigue behavior of RC beams strengthened with Carbon Fiber Reinforced Polymer (CFRP). Fatigue calculations are performed using a lamellar model that considers the fatigue behavior of the RC and CFRP strengthening materials during loading. The model’s output is compared to experimental data for four CFRP-strengthened beams, showing that the new model accurately predicted the deflection and strain of each one. In addition, various models for predicting the fatigue life of CFRP-strengthened RC beams were tested and a model capable of providing conservative fatigue life estimates was identified.

National Category
Infrastructure Engineering
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-2661 (URN)05094d5b-1bad-4729-bb96-6fb60f834d45 (Local ID)05094d5b-1bad-4729-bb96-6fb60f834d45 (Archive number)05094d5b-1bad-4729-bb96-6fb60f834d45 (OAI)
Note

Upprättat; 2015; 20150114 (mohsal)

Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-05-02
Mahal, M. (2015). Fatigue Behaviour of RC beams Strengthened with CFRP: Analytical and Experimental investigations (ed.). (Doctoral dissertation). Luleå tekniska universitet
Open this publication in new window or tab >>Fatigue Behaviour of RC beams Strengthened with CFRP: Analytical and Experimental investigations
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Repeated cyclic loading of reinforced concrete (RC) structures such as bridges can cause reduced service life and structure failure due to fatigue even when the stress ranges applied to the structural components are very low. These problems can be mitigated by using fiber-reinforced polymer (FRP) composites to increase the structures’ load carrying capacity and fatigue life or service life. Strengthening of this sort may be a suitable way to prolong the service life of concrete structures. FRP strengthening involves externally bonding a plate, sheet or rod of the strengthening material to the surface of the concrete member or placing the strengthening element in grooves cut into the member’s surface. The bonding of plates or sheets to the surface is often referred to as EBR (externally bonded reinforcement) whereas the placement of strengthening bars in grooves carved into the member’s surface is referred to as NSM (Near Surface Mounted) reinforcement. When this research project was initiated, it was not clear whether EBR or NSM strengthening was more effective at alleviating the effects of fatigue loading, and there were many aspects of their use that warranted further investigation. The main objectives of the work presented in this thesis were to study the behaviour of materials and structures under fatigue loading, to assess the structural challenges presented by fatigue loading of members strengthened with EBR plates or NSM bars, and to identify analytical models suitable for the design and analysis of FRP-strengthening elements and strengthened concrete members. The scientific approach adopted in this work is based on experimental fatigue loading tests of RC beams strengthened with EBR plates and NSM bars together with the development and assessment of analytical methods for describing the fatigue behaviour of tested strengthened beams and numerical models for predicting the behaviour of bond joints under fatigue loading. The analytical models were then verified against experimental results. The theoretical and experimental studies were supported by a state-of-the-art literature review that was conducted to gather existing knowledge concerning FRP strengthening of RC members and their fatigue behaviour at the material and structural levels

Place, publisher, year, edition, pages
Luleå tekniska universitet, 2015. p. 138
Series
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
National Category
Infrastructure Engineering
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-26738 (URN)fdcd24f9-cd32-46c1-821b-11ae03900ad9 (Local ID)978-91-7583-234-0 (ISBN)978-91-7583-235-7 (ISBN)fdcd24f9-cd32-46c1-821b-11ae03900ad9 (Archive number)fdcd24f9-cd32-46c1-821b-11ae03900ad9 (OAI)
Public defence
2015-03-27, F1031, Luleå tekniska universitet, Luleå, 10:00
Opponent
Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2023-11-29Bibliographically approved
Mahal, M., Blanksvärd, T., Täljsten, B. & Sas, G. (2015). Using digital image correlation to evaluate fatigue behavior of strengthened reinforced concrete beams (ed.). Engineering structures, 105, 277-288
Open this publication in new window or tab >>Using digital image correlation to evaluate fatigue behavior of strengthened reinforced concrete beams
2015 (English)In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 105, p. 277-288Article in journal (Refereed) Published
Abstract [en]

The fatigue behavior of reinforced concrete beams externally strengthened with carbon fiber reinforced polymer plates and near-surface mounted bars has been investigated using a digital image correlation (DIC) technique. Displacement fields obtained from digital images recorded during specific load cycles in fatigue tests are analyzed to provide information on crack width, beam deflection and curvature, and major principal strains to enable crack detection. The results obtained in this way were compared to data gathered using conventional sensors, revealing that the DIC technique provided very accurate and detailed information. The experimental results for plate-strengthened, bar-strengthened, and unstrengthened beams are discussed.

National Category
Infrastructure Engineering
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-3725 (URN)10.1016/j.engstruct.2015.10.017 (DOI)000365050000022 ()2-s2.0-84945264599 (Scopus ID)18f1496b-2709-4325-b0a8-5532d7d6e2d7 (Local ID)18f1496b-2709-4325-b0a8-5532d7d6e2d7 (Archive number)18f1496b-2709-4325-b0a8-5532d7d6e2d7 (OAI)
Note
Validerad; 2015; Nivå 2; 20150114 (mohsal)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Mahal, M., Blanksvärd, T. & Täljsten, B. (2014). FE modeling of FRP-concrete interface for very high cycle fatigue behavior (ed.). In: (Ed.), A. Milazzo; M.H. Aliabadi (Ed.), Advances in fracture and damage mechanics XII: selected, peer reviewed papers from the 12th International Conference on Fracture and Damage Mechanics (FDM 2013), September 17 - 19, 2013, Sardinia, Italy. Paper presented at International Conference on Fracture and Damage Mechanics : 17/09/2013 - 19/09/2013 (pp. 165-168). Durnten-Zurich: Trans Tech Publications Inc.
Open this publication in new window or tab >>FE modeling of FRP-concrete interface for very high cycle fatigue behavior
2014 (English)In: Advances in fracture and damage mechanics XII: selected, peer reviewed papers from the 12th International Conference on Fracture and Damage Mechanics (FDM 2013), September 17 - 19, 2013, Sardinia, Italy / [ed] A. Milazzo; M.H. Aliabadi, Durnten-Zurich: Trans Tech Publications Inc., 2014, p. 165-168Conference paper, Published paper (Refereed)
Abstract [en]

The fatigue damage of FRP-concrete interface is a major problem in strengthened structures subjected to fatigue loading. The available FRP-concrete interface models published in the literature usually deal with fracture mechanism approach, which is unsuitable for high cycle fatigue damage. In this study, a constitutive micro model is developed for FRP-concrete interface for high cycle fatigue and incorporated into a three dimensional finite-element program. Numerical analysis of a double lap joint is carried out, and the results show that the proposed model is reasonably accurate

Place, publisher, year, edition, pages
Durnten-Zurich: Trans Tech Publications Inc., 2014
Series
Key Engineering Materials, ISSN 1013-9826 ; 577/578
National Category
Infrastructure Engineering
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-35200 (URN)10.4028/www.scientific.net/KEM.577-578.165 (DOI)000336693900042 ()2-s2.0-84888610178 (Scopus ID)9a17763d-335f-4649-854a-fa19addfc7f9 (Local ID)9a17763d-335f-4649-854a-fa19addfc7f9 (Archive number)9a17763d-335f-4649-854a-fa19addfc7f9 (OAI)
Conference
International Conference on Fracture and Damage Mechanics : 17/09/2013 - 19/09/2013
Note
Godkänd; 2014; 20131210 (andbra)Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2018-07-10Bibliographically approved
Mahal, M., Blanksvärd, T. & Täljsten, B. (2013). Examination at a material and structural level of the fatigue life of beams strengthened with mineral or epoxy bonded FRPs: the state of the art (ed.). Advances in Structural Engineering, 16(7), 1329-1345
Open this publication in new window or tab >>Examination at a material and structural level of the fatigue life of beams strengthened with mineral or epoxy bonded FRPs: the state of the art
2013 (English)In: Advances in Structural Engineering, ISSN 1369-4332, E-ISSN 2048-4011, Vol. 16, no 7, p. 1329-1345Article in journal (Refereed) Published
Abstract [en]

This paper presents a state of the art review of different material combinations and applications of mineral-based and epoxy-based bonded Fiber Reinforced Polymers (FRP), used for the strengthening of concrete structures subjected to fatigue loading. In this review, models of the fatigue life at the material and structural level are presented. This study examines the mechanical behavior of the FRP-material, surface bonding behavior and concrete beams strengthened under fatigue loading with different types of FRP-systems. The parameters that are investigated are applied load value, time dependent effects, type of strengthened structures (shear, flexural or combined) and the configuration of sheets or plates. The building codes and researchers' recommendations are also discussed. As a result of this review, the reader will obtains an overview of suitable materials and methods for strengthening structures subjected to fatigue loading by referring to the estimated fatigue life of material and strengthening structures at various applied stress levels.

National Category
Infrastructure Engineering
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-4070 (URN)10.1260/1369-4332.16.7.1311 (DOI)000323357200011 ()2-s2.0-84883141667 (Scopus ID)1ee5cbc0-5c70-45e5-be4c-b935d845d3b8 (Local ID)1ee5cbc0-5c70-45e5-be4c-b935d845d3b8 (Archive number)1ee5cbc0-5c70-45e5-be4c-b935d845d3b8 (OAI)
Note
Validerad; 2013; 20130823 (thojoh)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2023-09-06Bibliographically approved
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