Ändra sökning
Avgränsa sökresultatet
1 - 8 av 8
RefereraExporteraLänk till träfflistan
Permanent länk
Referera
Referensformat
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf
Träffar per sida
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sortering
  • Standard (Relevans)
  • Författare A-Ö
  • Författare Ö-A
  • Titel A-Ö
  • Titel Ö-A
  • Publikationstyp A-Ö
  • Publikationstyp Ö-A
  • Äldst först
  • Nyast först
  • Skapad (Äldst först)
  • Skapad (Nyast först)
  • Senast uppdaterad (Äldst först)
  • Senast uppdaterad (Nyast först)
  • Disputationsdatum (tidigaste först)
  • Disputationsdatum (senaste först)
  • Standard (Relevans)
  • Författare A-Ö
  • Författare Ö-A
  • Titel A-Ö
  • Titel Ö-A
  • Publikationstyp A-Ö
  • Publikationstyp Ö-A
  • Äldst först
  • Nyast först
  • Skapad (Äldst först)
  • Skapad (Nyast först)
  • Senast uppdaterad (Äldst först)
  • Senast uppdaterad (Nyast först)
  • Disputationsdatum (tidigaste först)
  • Disputationsdatum (senaste först)
Markera
Maxantalet träffar du kan exportera från sökgränssnittet är 250. Vid större uttag använd dig av utsökningar.
  • 1.
    Mahal, Mohammed
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och -produktion.
    Experimental investigation of RC beams strengthened with FRP materials under monotonic and fatigue loads2016Rapport (Övrigt vetenskapligt)
    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.

  • 2.
    Mahal, Mohammed
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och -produktion.
    Fatigue Behaviour of RC beams Strengthened with CFRP: Analytical and Experimental investigations2015Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    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

  • 3.
    Mahal, Mohammed
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och -produktion.
    Blanksvärd, Thomas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och -produktion.
    Täljsten, Björn
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och -produktion.
    A two-scale damage model for high-cycle fatigue at the fiber-reinforced polymer-concrete interface2016Ingår i: Computers and Concrete, ISSN 1598-8198, Vol. 116, s. 12-20Artikel i tidskrift (Refereegranskat)
    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.

  • 4.
    Mahal, Mohammed
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och -produktion.
    Blanksvärd, Thomas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och -produktion.
    Täljsten, Björn
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och -produktion.
    Examination at a material and structural level of the fatigue life of beams strengthened with mineral or epoxy bonded FRPs: the state of the art2013Ingår i: Advances in Structural Engineering, ISSN 1369-4332, E-ISSN 2048-4011, Vol. 16, nr 7, s. 1329-1345Artikel i tidskrift (Refereegranskat)
    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.

  • 5.
    Mahal, Mohammed
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och -produktion.
    Blanksvärd, Thomas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och -produktion.
    Täljsten, Björn
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och -produktion.
    FE modeling of FRP-concrete interface for very high cycle fatigue behavior2014Ingår i: 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, s. 165-168Konferensbidrag (Refereegranskat)
    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

  • 6.
    Mahal, Mohammed
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och -produktion.
    Blanksvärd, Thomas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och -produktion.
    Täljsten, Björn
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och -produktion.
    Sas, Gabriel
    Northern Research Institute.
    Using digital image correlation to evaluate fatigue behavior of strengthened reinforced concrete beams2015Ingår i: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 105, s. 277-288Artikel i tidskrift (Refereegranskat)
    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.

  • 7.
    Mahal, Mohammed
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och -produktion.
    Täljsten, Björn
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och -produktion.
    Blanksvärd, Thomas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och -produktion.
    Experimental performance of RC beams strengthened with FRP materials under monotonic and fatigue loads2016Ingår i: Journal of composites for construction, ISSN 1090-0268, E-ISSN 1943-5614, Vol. 122, s. 126-139Artikel i tidskrift (Refereegranskat)
    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.

  • 8.
    Mahal, Mohammed
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och -produktion.
    Täljsten, Björn
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och -produktion.
    Blanksvärd, Thomas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och -produktion.
    Fatigue analysis of RC beams strengthened in flexure using CFRP2016Ingår i: Composite structures, ISSN 0263-8223, E-ISSN 1879-1085Artikel i tidskrift (Refereegranskat)
    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.

1 - 8 av 8
RefereraExporteraLänk till träfflistan
Permanent länk
Referera
Referensformat
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf